[PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[Thomas Weißschuh]

Finding the debug version of the vDSO is not trivial as there is no common
scheme where it is placed. That's especially problematic for CI testing.

The vDSO futex unlock mechanism requires for testing to have access to the
inner labels of the unlock assembly, which are only accessible via the
debug so.

Also for general debugging purposes it's convenient to have access to the
debug vDSO at a well defined place.

The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
regular 'make vdso_install' layout, including build-id symlinks to find
the correct file for each process.

The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.

On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
explicit dependency to avoid errors due to concurrent builds.

Suggested-by: Thomas Gleixner <tglx@kernel.org>
Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 Makefile            | 33 ++++++++++++++++++++++++++++++++-
 arch/x86/Makefile   |  3 +++
 init/Kconfig        | 10 ++++++++++
 kernel/Makefile     |  1 +
 kernel/vdso_debug.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index b9c5792c79e0..8049f10c27b2 100644
--- a/Makefile
+++ b/Makefile
@@ -298,7 +298,7 @@ no-dot-config-targets := $(clean-targets) \
 			 %asm-generic kernelversion %src-pkg dt_binding_check \
 			 dt_style_selftest \
 			 outputmakefile rustavailable rustfmt rustfmtcheck \
-			 run-command
+			 run-command have-vdso-debug
 no-sync-config-targets := $(no-dot-config-targets) %install modules_sign kernelrelease \
 			  image_name
 single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.rsi %.s %/
@@ -1539,6 +1539,37 @@ vdso_install: export INSTALL_FILES = $(vdso-install-y)
 vdso_install:
 	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vdsoinst
 
+# ---------------------------------------------------------------------------
+# vDSO embedded debug symbols
+
+PHONY += vdso_prepare
+
+# Build the targets in $(vdso-install-y)
+# Some architectures may do this already through vdso_prepare,
+# so add a dependency to avoid race conditions
+$(vdso-install-y): vdso_prepare prepare0 FORCE
+	@$(MAKE) $(build)=$(patsubst %/,%,$(dir $@)) $@
+
+tar-opts := --mtime='1970-01-01 00:00:00' --owner=0 --group=0 --sort=name --numeric-owner --mode=u=rw,go=r,a+X
+
+quiet_cmd_vdso_debug_tar_xz = VDSODBG $@
+      cmd_vdso_debug_tar_xz = \
+		rm -rf $(tmp-target); mkdir -p $(tmp-target)/vdso/; \
+		$(MAKE) quiet=@ MODLIB=$(tmp-target) vdso_install; \
+		$(TAR) $(tar-opts) -a -c -f $@ -C $(tmp-target)/vdso/ .
+
+targets += vdso_debug.tar.xz
+vdso_debug.tar.xz: $(vdso-install-y) FORCE
+	$(call if_changed,vdso_debug_tar_xz)
+
+ifdef CONFIG_IVDSODEBUG
+prepare: vdso_debug.tar.xz
+endif
+
+PHONY += have-vdso-debug
+have-vdso-debug:
+	@echo $(if $(vdso-install-y)$(vdso-install-),y,n)
+
 # ---------------------------------------------------------------------------
 # Tools
 
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 598f178102ee..b762fddb620e 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -316,6 +316,9 @@ vdso-install-$(CONFIG_X86_64)	   += arch/x86/entry/vdso/vdso64/vdso64.so.dbg
 vdso-install-$(CONFIG_X86_X32_ABI) += arch/x86/entry/vdso/vdso64/vdsox32.so.dbg
 vdso-install-$(CONFIG_COMPAT_32)   += arch/x86/entry/vdso/vdso32/vdso32.so.dbg
 
+# vdsox32.so.dbg is derived from vdso64.so.dbg. Avoid races with CONFIG_IVDSODEBUG
+arch/x86/entry/vdso/vdso64/vdsox32.so.dbg: arch/x86/entry/vdso/vdso64/vdso64.so.dbg
+
 archprepare: checkbin
 checkbin:
 ifdef CONFIG_MITIGATION_RETPOLINE
diff --git a/init/Kconfig b/init/Kconfig
index 5230d4879b1c..f09132a44264 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -801,6 +801,16 @@ config IKHEADERS
 	  or similar programs.  If you build the headers as a module, a module called
 	  kheaders.ko is built which can be loaded on-demand to get access to headers.
 
+config IVDSODEBUG
+	tristate "Enable vDSO debug information through /sys/kernel/vdso_debug.tar.xz"
+	depends on SYSFS
+	depends on "$(shell,make have-vdso-debug)"
+	help
+	  This option enables access to the vDSO debug information. That can be
+	  used to debug applications and test the vDSO implementation.
+
+	  If configured as M the module will be called vdso_debug.ko.
+
 config LOG_BUF_SHIFT
 	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 	range 12 25
diff --git a/kernel/Makefile b/kernel/Makefile
index 1e1a31673577..8adcc26ef859 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -93,6 +93,7 @@ obj-$(CONFIG_USER_NS) += user_namespace.o
 obj-$(CONFIG_PID_NS) += pid_namespace.o
 obj-$(CONFIG_IKCONFIG) += configs.o
 obj-$(CONFIG_IKHEADERS) += kheaders.o
+obj-$(CONFIG_IVDSODEBUG) += vdso_debug.o
 obj-$(CONFIG_SMP) += stop_machine.o
 obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
 obj-$(CONFIG_AUDITSYSCALL) += auditsc.o audit_watch.o audit_fsnotify.o audit_tree.o
diff --git a/kernel/vdso_debug.c b/kernel/vdso_debug.c
new file mode 100644
index 000000000000..72d4f11327fc
--- /dev/null
+++ b/kernel/vdso_debug.c
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/cache.h>
+#include <linux/init.h>
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/sysfs.h>
+
+asm (
+"	.pushsection .rodata, \"a\"	\n"
+"	.global vdso_debug_data		\n"
+"vdso_debug_data:			\n"
+"	.incbin \"vdso_debug.tar.xz\"	\n"
+"	.global vdso_debug_data_end	\n"
+"vdso_debug_data_end:			\n"
+"	.popsection			\n"
+);
+
+extern char vdso_debug_data[];
+extern char vdso_debug_data_end[];
+
+static struct bin_attribute vdso_debug_attr __ro_after_init =
+	__BIN_ATTR_SIMPLE_RO(vdso_debug.tar.xz, 0444);
+
+static int __init vdso_debug_init(void)
+{
+	vdso_debug_attr.private = vdso_debug_data;
+	vdso_debug_attr.size = vdso_debug_data_end - vdso_debug_data;
+
+	return sysfs_create_bin_file(kernel_kobj, &vdso_debug_attr);
+}
+
+static void __exit vdso_debug_exit(void)
+{
+	sysfs_remove_bin_file(kernel_kobj, &vdso_debug_attr);
+}
+
+module_init(vdso_debug_init);
+module_exit(vdso_debug_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Thomas Weißschuh <thomas.weissschuh@linutronix.de>");
+MODULE_DESCRIPTION("Provide vDSO debug information at runtime");

---
base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
change-id: 20260624-vdso-sysfs-abfd14fde5a7

Best regards,
--  
Thomas Weißschuh <thomas.weissschuh@linutronix.de>

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[André Almeida]

Em 08/07/2026 10:56, Thomas Weißschuh escreveu:
> Finding the debug version of the vDSO is not trivial as there is no common
> scheme where it is placed. That's especially problematic for CI testing.
> 
> The vDSO futex unlock mechanism requires for testing to have access to the
> inner labels of the unlock assembly, which are only accessible via the
> debug so.
> 
> Also for general debugging purposes it's convenient to have access to the
> debug vDSO at a well defined place.
> 
> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
> regular 'make vdso_install' layout, including build-id symlinks to find
> the correct file for each process.
> 
> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
> 
> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
> explicit dependency to avoid errors due to concurrent builds.
> 
> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> ---

Thanks for your patch! Tested in arm64 (qemu) and it worked fine. I was 
just expecting that the file would be called "vdso.so.dbg", not "vdso.so".

Tested-by: André Almeida <andrealmeid@igalia.com>

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[André Almeida]

Em 08/07/2026 12:28, André Almeida escreveu:
> Em 08/07/2026 10:56, Thomas Weißschuh escreveu:
>> Finding the debug version of the vDSO is not trivial as there is no 
>> common
>> scheme where it is placed. That's especially problematic for CI testing.
>>
>> The vDSO futex unlock mechanism requires for testing to have access to 
>> the
>> inner labels of the unlock assembly, which are only accessible via the
>> debug so.
>>
>> Also for general debugging purposes it's convenient to have access to the
>> debug vDSO at a well defined place.
>>
>> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
>> regular 'make vdso_install' layout, including build-id symlinks to find
>> the correct file for each process.
>>
>> The design is kept close to the ones of the similar IKCONFIG and 
>> IKHEADERS.
>>
>> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
>> explicit dependency to avoid errors due to concurrent builds.
>>
>> Suggested-by: Thomas Gleixner <tglx@kernel.org>
>> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
>> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>> ---
> 
> Thanks for your patch! Tested in arm64 (qemu) and it worked fine. I was 
> just expecting that the file would be called "vdso.so.dbg", not "vdso.so".
> 
> Tested-by: André Almeida <andrealmeid@igalia.com>

Also, how do you suggest to integrate this with kselftests? Maybe adding 
an untar command to futex/functional/run.sh?

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[Thomas Weißschuh]

On Wed, Jul 15, 2026 at 09:29:35AM -0300, André Almeida wrote:
> Em 08/07/2026 12:28, André Almeida escreveu:
> > Em 08/07/2026 10:56, Thomas Weißschuh escreveu:
> > > Finding the debug version of the vDSO is not trivial as there is no
> > > common
> > > scheme where it is placed. That's especially problematic for CI testing.
> > > 
> > > The vDSO futex unlock mechanism requires for testing to have access
> > > to the
> > > inner labels of the unlock assembly, which are only accessible via the
> > > debug so.
> > > 
> > > Also for general debugging purposes it's convenient to have access to the
> > > debug vDSO at a well defined place.
> > > 
> > > The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
> > > regular 'make vdso_install' layout, including build-id symlinks to find
> > > the correct file for each process.
> > > 
> > > The design is kept close to the ones of the similar IKCONFIG and
> > > IKHEADERS.
> > > 
> > > On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
> > > explicit dependency to avoid errors due to concurrent builds.
> > > 
> > > Suggested-by: Thomas Gleixner <tglx@kernel.org>
> > > Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
> > > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> > > ---
> > 
> > Thanks for your patch! Tested in arm64 (qemu) and it worked fine. I was
> > just expecting that the file would be called "vdso.so.dbg", not
> > "vdso.so".

That is due to scripts/Makefile.vdsoinst:

dest := $(install-dir)/$$(patsubst %.dbg,%,$$(notdir $(1)))

> > Tested-by: André Almeida <andrealmeid@igalia.com>

Thanks!

> Also, how do you suggest to integrate this with kselftests? Maybe adding an
> untar command to futex/functional/run.sh?

In the current implementation, yes. But it would also be possible to have a
proper virtual directory tree, albeit with higher implementation consts.


Thomas

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[Vincenzo Frascino]

On 08/07/2026 14:56, Thomas Weißschuh wrote:
> Finding the debug version of the vDSO is not trivial as there is no common
> scheme where it is placed. That's especially problematic for CI testing.
> 
> The vDSO futex unlock mechanism requires for testing to have access to the
> inner labels of the unlock assembly, which are only accessible via the
> debug so.
> 
> Also for general debugging purposes it's convenient to have access to the
> debug vDSO at a well defined place.
> 
> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
> regular 'make vdso_install' layout, including build-id symlinks to find
> the correct file for each process.
> 
> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
> 
> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
> explicit dependency to avoid errors due to concurrent builds.
> 
> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

This is a really good idea. Thanks!

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

> ---
>  Makefile            | 33 ++++++++++++++++++++++++++++++++-
>  arch/x86/Makefile   |  3 +++
>  init/Kconfig        | 10 ++++++++++
>  kernel/Makefile     |  1 +
>  kernel/vdso_debug.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 89 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index b9c5792c79e0..8049f10c27b2 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -298,7 +298,7 @@ no-dot-config-targets := $(clean-targets) \
>  			 %asm-generic kernelversion %src-pkg dt_binding_check \
>  			 dt_style_selftest \
>  			 outputmakefile rustavailable rustfmt rustfmtcheck \
> -			 run-command
> +			 run-command have-vdso-debug
>  no-sync-config-targets := $(no-dot-config-targets) %install modules_sign kernelrelease \
>  			  image_name
>  single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.rsi %.s %/
> @@ -1539,6 +1539,37 @@ vdso_install: export INSTALL_FILES = $(vdso-install-y)
>  vdso_install:
>  	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vdsoinst
>  
> +# ---------------------------------------------------------------------------
> +# vDSO embedded debug symbols
> +
> +PHONY += vdso_prepare
> +
> +# Build the targets in $(vdso-install-y)
> +# Some architectures may do this already through vdso_prepare,
> +# so add a dependency to avoid race conditions
> +$(vdso-install-y): vdso_prepare prepare0 FORCE
> +	@$(MAKE) $(build)=$(patsubst %/,%,$(dir $@)) $@
> +
> +tar-opts := --mtime='1970-01-01 00:00:00' --owner=0 --group=0 --sort=name --numeric-owner --mode=u=rw,go=r,a+X
> +
> +quiet_cmd_vdso_debug_tar_xz = VDSODBG $@
> +      cmd_vdso_debug_tar_xz = \
> +		rm -rf $(tmp-target); mkdir -p $(tmp-target)/vdso/; \
> +		$(MAKE) quiet=@ MODLIB=$(tmp-target) vdso_install; \
> +		$(TAR) $(tar-opts) -a -c -f $@ -C $(tmp-target)/vdso/ .
> +
> +targets += vdso_debug.tar.xz
> +vdso_debug.tar.xz: $(vdso-install-y) FORCE
> +	$(call if_changed,vdso_debug_tar_xz)
> +
> +ifdef CONFIG_IVDSODEBUG
> +prepare: vdso_debug.tar.xz
> +endif
> +
> +PHONY += have-vdso-debug
> +have-vdso-debug:
> +	@echo $(if $(vdso-install-y)$(vdso-install-),y,n)
> +
>  # ---------------------------------------------------------------------------
>  # Tools
>  
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 598f178102ee..b762fddb620e 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -316,6 +316,9 @@ vdso-install-$(CONFIG_X86_64)	   += arch/x86/entry/vdso/vdso64/vdso64.so.dbg
>  vdso-install-$(CONFIG_X86_X32_ABI) += arch/x86/entry/vdso/vdso64/vdsox32.so.dbg
>  vdso-install-$(CONFIG_COMPAT_32)   += arch/x86/entry/vdso/vdso32/vdso32.so.dbg
>  
> +# vdsox32.so.dbg is derived from vdso64.so.dbg. Avoid races with CONFIG_IVDSODEBUG
> +arch/x86/entry/vdso/vdso64/vdsox32.so.dbg: arch/x86/entry/vdso/vdso64/vdso64.so.dbg
> +
>  archprepare: checkbin
>  checkbin:
>  ifdef CONFIG_MITIGATION_RETPOLINE
> diff --git a/init/Kconfig b/init/Kconfig
> index 5230d4879b1c..f09132a44264 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -801,6 +801,16 @@ config IKHEADERS
>  	  or similar programs.  If you build the headers as a module, a module called
>  	  kheaders.ko is built which can be loaded on-demand to get access to headers.
>  
> +config IVDSODEBUG
> +	tristate "Enable vDSO debug information through /sys/kernel/vdso_debug.tar.xz"
> +	depends on SYSFS
> +	depends on "$(shell,make have-vdso-debug)"
> +	help
> +	  This option enables access to the vDSO debug information. That can be
> +	  used to debug applications and test the vDSO implementation.
> +
> +	  If configured as M the module will be called vdso_debug.ko.
> +
>  config LOG_BUF_SHIFT
>  	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
>  	range 12 25
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 1e1a31673577..8adcc26ef859 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -93,6 +93,7 @@ obj-$(CONFIG_USER_NS) += user_namespace.o
>  obj-$(CONFIG_PID_NS) += pid_namespace.o
>  obj-$(CONFIG_IKCONFIG) += configs.o
>  obj-$(CONFIG_IKHEADERS) += kheaders.o
> +obj-$(CONFIG_IVDSODEBUG) += vdso_debug.o
>  obj-$(CONFIG_SMP) += stop_machine.o
>  obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
>  obj-$(CONFIG_AUDITSYSCALL) += auditsc.o audit_watch.o audit_fsnotify.o audit_tree.o
> diff --git a/kernel/vdso_debug.c b/kernel/vdso_debug.c
> new file mode 100644
> index 000000000000..72d4f11327fc
> --- /dev/null
> +++ b/kernel/vdso_debug.c
> @@ -0,0 +1,43 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/cache.h>
> +#include <linux/init.h>
> +#include <linux/kobject.h>
> +#include <linux/module.h>
> +#include <linux/sysfs.h>
> +
> +asm (
> +"	.pushsection .rodata, \"a\"	\n"
> +"	.global vdso_debug_data		\n"
> +"vdso_debug_data:			\n"
> +"	.incbin \"vdso_debug.tar.xz\"	\n"
> +"	.global vdso_debug_data_end	\n"
> +"vdso_debug_data_end:			\n"
> +"	.popsection			\n"
> +);
> +
> +extern char vdso_debug_data[];
> +extern char vdso_debug_data_end[];
> +
> +static struct bin_attribute vdso_debug_attr __ro_after_init =
> +	__BIN_ATTR_SIMPLE_RO(vdso_debug.tar.xz, 0444);
> +
> +static int __init vdso_debug_init(void)
> +{
> +	vdso_debug_attr.private = vdso_debug_data;
> +	vdso_debug_attr.size = vdso_debug_data_end - vdso_debug_data;
> +
> +	return sysfs_create_bin_file(kernel_kobj, &vdso_debug_attr);
> +}
> +
> +static void __exit vdso_debug_exit(void)
> +{
> +	sysfs_remove_bin_file(kernel_kobj, &vdso_debug_attr);
> +}
> +
> +module_init(vdso_debug_init);
> +module_exit(vdso_debug_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Thomas Weißschuh <thomas.weissschuh@linutronix.de>");
> +MODULE_DESCRIPTION("Provide vDSO debug information at runtime");
> 
> ---
> base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
> change-id: 20260624-vdso-sysfs-abfd14fde5a7
> 
> Best regards,
> --  
> Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> 

-- 
Regards,
Vincenzo

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[H. Peter Anvin]

On July 9, 2026 2:57:09 AM PDT, Vincenzo Frascino <vincenzo.frascino@arm.com> wrote:
>
>
>On 08/07/2026 14:56, Thomas Weißschuh wrote:
>> Finding the debug version of the vDSO is not trivial as there is no common
>> scheme where it is placed. That's especially problematic for CI testing.
>> 
>> The vDSO futex unlock mechanism requires for testing to have access to the
>> inner labels of the unlock assembly, which are only accessible via the
>> debug so.
>> 
>> Also for general debugging purposes it's convenient to have access to the
>> debug vDSO at a well defined place.
>> 
>> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
>> regular 'make vdso_install' layout, including build-id symlinks to find
>> the correct file for each process.
>> 
>> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
>> 
>> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
>> explicit dependency to avoid errors due to concurrent builds.
>> 
>> Suggested-by: Thomas Gleixner <tglx@kernel.org>
>> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
>> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>
>This is a really good idea. Thanks!
>
>Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
>
>> ---
>>  Makefile            | 33 ++++++++++++++++++++++++++++++++-
>>  arch/x86/Makefile   |  3 +++
>>  init/Kconfig        | 10 ++++++++++
>>  kernel/Makefile     |  1 +
>>  kernel/vdso_debug.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>>  5 files changed, 89 insertions(+), 1 deletion(-)
>> 
>> diff --git a/Makefile b/Makefile
>> index b9c5792c79e0..8049f10c27b2 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -298,7 +298,7 @@ no-dot-config-targets := $(clean-targets) \
>>  			 %asm-generic kernelversion %src-pkg dt_binding_check \
>>  			 dt_style_selftest \
>>  			 outputmakefile rustavailable rustfmt rustfmtcheck \
>> -			 run-command
>> +			 run-command have-vdso-debug
>>  no-sync-config-targets := $(no-dot-config-targets) %install modules_sign kernelrelease \
>>  			  image_name
>>  single-targets := %.a %.i %.ko %.lds %.ll %.lst %.mod %.o %.rsi %.s %/
>> @@ -1539,6 +1539,37 @@ vdso_install: export INSTALL_FILES = $(vdso-install-y)
>>  vdso_install:
>>  	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.vdsoinst
>>  
>> +# ---------------------------------------------------------------------------
>> +# vDSO embedded debug symbols
>> +
>> +PHONY += vdso_prepare
>> +
>> +# Build the targets in $(vdso-install-y)
>> +# Some architectures may do this already through vdso_prepare,
>> +# so add a dependency to avoid race conditions
>> +$(vdso-install-y): vdso_prepare prepare0 FORCE
>> +	@$(MAKE) $(build)=$(patsubst %/,%,$(dir $@)) $@
>> +
>> +tar-opts := --mtime='1970-01-01 00:00:00' --owner=0 --group=0 --sort=name --numeric-owner --mode=u=rw,go=r,a+X
>> +
>> +quiet_cmd_vdso_debug_tar_xz = VDSODBG $@
>> +      cmd_vdso_debug_tar_xz = \
>> +		rm -rf $(tmp-target); mkdir -p $(tmp-target)/vdso/; \
>> +		$(MAKE) quiet=@ MODLIB=$(tmp-target) vdso_install; \
>> +		$(TAR) $(tar-opts) -a -c -f $@ -C $(tmp-target)/vdso/ .
>> +
>> +targets += vdso_debug.tar.xz
>> +vdso_debug.tar.xz: $(vdso-install-y) FORCE
>> +	$(call if_changed,vdso_debug_tar_xz)
>> +
>> +ifdef CONFIG_IVDSODEBUG
>> +prepare: vdso_debug.tar.xz
>> +endif
>> +
>> +PHONY += have-vdso-debug
>> +have-vdso-debug:
>> +	@echo $(if $(vdso-install-y)$(vdso-install-),y,n)
>> +
>>  # ---------------------------------------------------------------------------
>>  # Tools
>>  
>> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
>> index 598f178102ee..b762fddb620e 100644
>> --- a/arch/x86/Makefile
>> +++ b/arch/x86/Makefile
>> @@ -316,6 +316,9 @@ vdso-install-$(CONFIG_X86_64)	   += arch/x86/entry/vdso/vdso64/vdso64.so.dbg
>>  vdso-install-$(CONFIG_X86_X32_ABI) += arch/x86/entry/vdso/vdso64/vdsox32.so.dbg
>>  vdso-install-$(CONFIG_COMPAT_32)   += arch/x86/entry/vdso/vdso32/vdso32.so.dbg
>>  
>> +# vdsox32.so.dbg is derived from vdso64.so.dbg. Avoid races with CONFIG_IVDSODEBUG
>> +arch/x86/entry/vdso/vdso64/vdsox32.so.dbg: arch/x86/entry/vdso/vdso64/vdso64.so.dbg
>> +
>>  archprepare: checkbin
>>  checkbin:
>>  ifdef CONFIG_MITIGATION_RETPOLINE
>> diff --git a/init/Kconfig b/init/Kconfig
>> index 5230d4879b1c..f09132a44264 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -801,6 +801,16 @@ config IKHEADERS
>>  	  or similar programs.  If you build the headers as a module, a module called
>>  	  kheaders.ko is built which can be loaded on-demand to get access to headers.
>>  
>> +config IVDSODEBUG
>> +	tristate "Enable vDSO debug information through /sys/kernel/vdso_debug.tar.xz"
>> +	depends on SYSFS
>> +	depends on "$(shell,make have-vdso-debug)"
>> +	help
>> +	  This option enables access to the vDSO debug information. That can be
>> +	  used to debug applications and test the vDSO implementation.
>> +
>> +	  If configured as M the module will be called vdso_debug.ko.
>> +
>>  config LOG_BUF_SHIFT
>>  	int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
>>  	range 12 25
>> diff --git a/kernel/Makefile b/kernel/Makefile
>> index 1e1a31673577..8adcc26ef859 100644
>> --- a/kernel/Makefile
>> +++ b/kernel/Makefile
>> @@ -93,6 +93,7 @@ obj-$(CONFIG_USER_NS) += user_namespace.o
>>  obj-$(CONFIG_PID_NS) += pid_namespace.o
>>  obj-$(CONFIG_IKCONFIG) += configs.o
>>  obj-$(CONFIG_IKHEADERS) += kheaders.o
>> +obj-$(CONFIG_IVDSODEBUG) += vdso_debug.o
>>  obj-$(CONFIG_SMP) += stop_machine.o
>>  obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
>>  obj-$(CONFIG_AUDITSYSCALL) += auditsc.o audit_watch.o audit_fsnotify.o audit_tree.o
>> diff --git a/kernel/vdso_debug.c b/kernel/vdso_debug.c
>> new file mode 100644
>> index 000000000000..72d4f11327fc
>> --- /dev/null
>> +++ b/kernel/vdso_debug.c
>> @@ -0,0 +1,43 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +#include <linux/cache.h>
>> +#include <linux/init.h>
>> +#include <linux/kobject.h>
>> +#include <linux/module.h>
>> +#include <linux/sysfs.h>
>> +
>> +asm (
>> +"	.pushsection .rodata, \"a\"	\n"
>> +"	.global vdso_debug_data		\n"
>> +"vdso_debug_data:			\n"
>> +"	.incbin \"vdso_debug.tar.xz\"	\n"
>> +"	.global vdso_debug_data_end	\n"
>> +"vdso_debug_data_end:			\n"
>> +"	.popsection			\n"
>> +);
>> +
>> +extern char vdso_debug_data[];
>> +extern char vdso_debug_data_end[];
>> +
>> +static struct bin_attribute vdso_debug_attr __ro_after_init =
>> +	__BIN_ATTR_SIMPLE_RO(vdso_debug.tar.xz, 0444);
>> +
>> +static int __init vdso_debug_init(void)
>> +{
>> +	vdso_debug_attr.private = vdso_debug_data;
>> +	vdso_debug_attr.size = vdso_debug_data_end - vdso_debug_data;
>> +
>> +	return sysfs_create_bin_file(kernel_kobj, &vdso_debug_attr);
>> +}
>> +
>> +static void __exit vdso_debug_exit(void)
>> +{
>> +	sysfs_remove_bin_file(kernel_kobj, &vdso_debug_attr);
>> +}
>> +
>> +module_init(vdso_debug_init);
>> +module_exit(vdso_debug_exit);
>> +
>> +MODULE_LICENSE("GPL");
>> +MODULE_AUTHOR("Thomas Weißschuh <thomas.weissschuh@linutronix.de>");
>> +MODULE_DESCRIPTION("Provide vDSO debug information at runtime");
>> 
>> ---
>> base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
>> change-id: 20260624-vdso-sysfs-abfd14fde5a7
>> 
>> Best regards,
>> --  
>> Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>> 
>

Why stuff them into a tarball?

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[Thomas Weißschuh]

On Thu, Jul 09, 2026 at 12:06:07PM -0700, H. Peter Anvin wrote:
> On July 9, 2026 2:57:09 AM PDT, Vincenzo Frascino <vincenzo.frascino@arm.com> wrote:
> >On 08/07/2026 14:56, Thomas Weißschuh wrote:
> >> Finding the debug version of the vDSO is not trivial as there is no common
> >> scheme where it is placed. That's especially problematic for CI testing.
> >> 
> >> The vDSO futex unlock mechanism requires for testing to have access to the
> >> inner labels of the unlock assembly, which are only accessible via the
> >> debug so.
> >> 
> >> Also for general debugging purposes it's convenient to have access to the
> >> debug vDSO at a well defined place.
> >> 
> >> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
> >> regular 'make vdso_install' layout, including build-id symlinks to find
> >> the correct file for each process.
> >> 
> >> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
> >> 
> >> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
> >> explicit dependency to avoid errors due to concurrent builds.
> >> 
> >> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> >> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
> >> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>

(...)

> Why stuff them into a tarball?

Because it was the easiest solution to implement and has been sufficient
for IKHEADERS so far. I don't see a clearly winning solution among the
possibilities to expose a directory:

* Use plain sysfs:
  Requires a new code generator and potentially changes to sysfs

* Use a read-only filesystem like cramfs/erofs:
  Introduces new build-time and runtime dependencies

* Add a new filesystem backed by a tarball or cpio archive:
  Lot's of complexity and work to implement

But I am open to discussions and other ideas.


Thomas

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[H. Peter Anvin]

On July 9, 2026 11:36:25 PM PDT, "Thomas Weißschuh" <thomas.weissschuh@linutronix.de> wrote:
>On Thu, Jul 09, 2026 at 12:06:07PM -0700, H. Peter Anvin wrote:
>> On July 9, 2026 2:57:09 AM PDT, Vincenzo Frascino <vincenzo.frascino@arm.com> wrote:
>> >On 08/07/2026 14:56, Thomas Weißschuh wrote:
>> >> Finding the debug version of the vDSO is not trivial as there is no common
>> >> scheme where it is placed. That's especially problematic for CI testing.
>> >> 
>> >> The vDSO futex unlock mechanism requires for testing to have access to the
>> >> inner labels of the unlock assembly, which are only accessible via the
>> >> debug so.
>> >> 
>> >> Also for general debugging purposes it's convenient to have access to the
>> >> debug vDSO at a well defined place.
>> >> 
>> >> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
>> >> regular 'make vdso_install' layout, including build-id symlinks to find
>> >> the correct file for each process.
>> >> 
>> >> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
>> >> 
>> >> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
>> >> explicit dependency to avoid errors due to concurrent builds.
>> >> 
>> >> Suggested-by: Thomas Gleixner <tglx@kernel.org>
>> >> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
>> >> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>
>(...)
>
>> Why stuff them into a tarball?
>
>Because it was the easiest solution to implement and has been sufficient
>for IKHEADERS so far. I don't see a clearly winning solution among the
>possibilities to expose a directory:
>
>* Use plain sysfs:
>  Requires a new code generator and potentially changes to sysfs
>
>* Use a read-only filesystem like cramfs/erofs:
>  Introduces new build-time and runtime dependencies
>
>* Add a new filesystem backed by a tarball or cpio archive:
>  Lot's of complexity and work to implement
>
>But I am open to discussions and other ideas.
>
>
>Thomas

I discussed this with GregKH a while ago, in the context of eventually making the vdso an actual mapping of a virtual file. According to him it should be quite simple in sysfs; I got a bit stumped on the necessary hooks (the kernel needs to keep track of where the vdso lives in the address space.)

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[Thomas Weißschuh]

On Fri, Jul 10, 2026 at 12:32:55AM -0700, H. Peter Anvin wrote:
> On July 9, 2026 11:36:25 PM PDT, "Thomas Weißschuh" <thomas.weissschuh@linutronix.de> wrote:
> >On Thu, Jul 09, 2026 at 12:06:07PM -0700, H. Peter Anvin wrote:
> >> On July 9, 2026 2:57:09 AM PDT, Vincenzo Frascino <vincenzo.frascino@arm.com> wrote:
> >> >On 08/07/2026 14:56, Thomas Weißschuh wrote:
> >> >> Finding the debug version of the vDSO is not trivial as there is no common
> >> >> scheme where it is placed. That's especially problematic for CI testing.
> >> >> 
> >> >> The vDSO futex unlock mechanism requires for testing to have access to the
> >> >> inner labels of the unlock assembly, which are only accessible via the
> >> >> debug so.
> >> >> 
> >> >> Also for general debugging purposes it's convenient to have access to the
> >> >> debug vDSO at a well defined place.
> >> >> 
> >> >> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
> >> >> regular 'make vdso_install' layout, including build-id symlinks to find
> >> >> the correct file for each process.
> >> >> 
> >> >> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
> >> >> 
> >> >> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
> >> >> explicit dependency to avoid errors due to concurrent builds.
> >> >> 
> >> >> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> >> >> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
> >> >> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> >
> >(...)
> >
> >> Why stuff them into a tarball?
> >
> >Because it was the easiest solution to implement and has been sufficient
> >for IKHEADERS so far. I don't see a clearly winning solution among the
> >possibilities to expose a directory:
> >
> >* Use plain sysfs:
> >  Requires a new code generator and potentially changes to sysfs
> >
> >* Use a read-only filesystem like cramfs/erofs:
> >  Introduces new build-time and runtime dependencies
> >
> >* Add a new filesystem backed by a tarball or cpio archive:
> >  Lot's of complexity and work to implement
> >
> >But I am open to discussions and other ideas.
> 
> I discussed this with GregKH a while ago, in the context of eventually making
> the vdso an actual mapping of a virtual file. According to him it should be
> quite simple in sysfs; I got a bit stumped on the necessary hooks (the kernel
> needs to keep track of where the vdso lives in the address space.)

Interesting idea, I will take a look at it.

Today the vDSO mapped into userspace is a stripped version. For the
debugging usecase however we want the unstripped one.
Also it won't help with debugging a coredump.


Thomas

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[H. Peter Anvin]

On July 10, 2026 12:41:31 AM PDT, "Thomas Weißschuh" <thomas.weissschuh@linutronix.de> wrote:
>On Fri, Jul 10, 2026 at 12:32:55AM -0700, H. Peter Anvin wrote:
>> On July 9, 2026 11:36:25 PM PDT, "Thomas Weißschuh" <thomas.weissschuh@linutronix.de> wrote:
>> >On Thu, Jul 09, 2026 at 12:06:07PM -0700, H. Peter Anvin wrote:
>> >> On July 9, 2026 2:57:09 AM PDT, Vincenzo Frascino <vincenzo.frascino@arm.com> wrote:
>> >> >On 08/07/2026 14:56, Thomas Weißschuh wrote:
>> >> >> Finding the debug version of the vDSO is not trivial as there is no common
>> >> >> scheme where it is placed. That's especially problematic for CI testing.
>> >> >> 
>> >> >> The vDSO futex unlock mechanism requires for testing to have access to the
>> >> >> inner labels of the unlock assembly, which are only accessible via the
>> >> >> debug so.
>> >> >> 
>> >> >> Also for general debugging purposes it's convenient to have access to the
>> >> >> debug vDSO at a well defined place.
>> >> >> 
>> >> >> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
>> >> >> regular 'make vdso_install' layout, including build-id symlinks to find
>> >> >> the correct file for each process.
>> >> >> 
>> >> >> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
>> >> >> 
>> >> >> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
>> >> >> explicit dependency to avoid errors due to concurrent builds.
>> >> >> 
>> >> >> Suggested-by: Thomas Gleixner <tglx@kernel.org>
>> >> >> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
>> >> >> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>> >
>> >(...)
>> >
>> >> Why stuff them into a tarball?
>> >
>> >Because it was the easiest solution to implement and has been sufficient
>> >for IKHEADERS so far. I don't see a clearly winning solution among the
>> >possibilities to expose a directory:
>> >
>> >* Use plain sysfs:
>> >  Requires a new code generator and potentially changes to sysfs
>> >
>> >* Use a read-only filesystem like cramfs/erofs:
>> >  Introduces new build-time and runtime dependencies
>> >
>> >* Add a new filesystem backed by a tarball or cpio archive:
>> >  Lot's of complexity and work to implement
>> >
>> >But I am open to discussions and other ideas.
>> 
>> I discussed this with GregKH a while ago, in the context of eventually making
>> the vdso an actual mapping of a virtual file. According to him it should be
>> quite simple in sysfs; I got a bit stumped on the necessary hooks (the kernel
>> needs to keep track of where the vdso lives in the address space.)
>
>Interesting idea, I will take a look at it.
>
>Today the vDSO mapped into userspace is a stripped version. For the
>debugging usecase however we want the unstripped one.
>Also it won't help with debugging a coredump.
>
>
>Thomas

Why wouldn't it??

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[Thomas Weißschuh]

On Fri, Jul 10, 2026 at 11:34:48AM -0700, H. Peter Anvin wrote:
> On July 10, 2026 12:41:31 AM PDT, "Thomas Weißschuh" <thomas.weissschuh@linutronix.de> wrote:
> >On Fri, Jul 10, 2026 at 12:32:55AM -0700, H. Peter Anvin wrote:
> >> On July 9, 2026 11:36:25 PM PDT, "Thomas Weißschuh" <thomas.weissschuh@linutronix.de> wrote:
> >> >On Thu, Jul 09, 2026 at 12:06:07PM -0700, H. Peter Anvin wrote:
> >> >> On July 9, 2026 2:57:09 AM PDT, Vincenzo Frascino <vincenzo.frascino@arm.com> wrote:
> >> >> >On 08/07/2026 14:56, Thomas Weißschuh wrote:
> >> >> >> Finding the debug version of the vDSO is not trivial as there is no common
> >> >> >> scheme where it is placed. That's especially problematic for CI testing.
> >> >> >> 
> >> >> >> The vDSO futex unlock mechanism requires for testing to have access to the
> >> >> >> inner labels of the unlock assembly, which are only accessible via the
> >> >> >> debug so.
> >> >> >> 
> >> >> >> Also for general debugging purposes it's convenient to have access to the
> >> >> >> debug vDSO at a well defined place.
> >> >> >> 
> >> >> >> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
> >> >> >> regular 'make vdso_install' layout, including build-id symlinks to find
> >> >> >> the correct file for each process.
> >> >> >> 
> >> >> >> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
> >> >> >> 
> >> >> >> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
> >> >> >> explicit dependency to avoid errors due to concurrent builds.
> >> >> >> 
> >> >> >> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> >> >> >> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
> >> >> >> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> >> >
> >> >(...)
> >> >
> >> >> Why stuff them into a tarball?
> >> >
> >> >Because it was the easiest solution to implement and has been sufficient
> >> >for IKHEADERS so far. I don't see a clearly winning solution among the
> >> >possibilities to expose a directory:
> >> >
> >> >* Use plain sysfs:
> >> >  Requires a new code generator and potentially changes to sysfs
> >> >
> >> >* Use a read-only filesystem like cramfs/erofs:
> >> >  Introduces new build-time and runtime dependencies
> >> >
> >> >* Add a new filesystem backed by a tarball or cpio archive:
> >> >  Lot's of complexity and work to implement
> >> >
> >> >But I am open to discussions and other ideas.
> >> 
> >> I discussed this with GregKH a while ago, in the context of eventually making
> >> the vdso an actual mapping of a virtual file. According to him it should be
> >> quite simple in sysfs; I got a bit stumped on the necessary hooks (the kernel
> >> needs to keep track of where the vdso lives in the address space.)
> >
> >Interesting idea, I will take a look at it.

What would be the advantages?

How would this handle the fact that the data page mapping needs to be fixed
next to the code one? Should the data page mapping also be a virtual file?

> >Today the vDSO mapped into userspace is a stripped version. For the
> >debugging usecase however we want the unstripped one.

> >Also it won't help with debugging a coredump.
> Why wouldn't it??

I can't reconstruct what I was thinking here. Sorry for the noise.


Thomas

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[Nicolas Schier]

On 2026-07-08 15:56 +0200, Thomas Weißschuh wrote:
> Finding the debug version of the vDSO is not trivial as there is no common
> scheme where it is placed. That's especially problematic for CI testing.
> 
> The vDSO futex unlock mechanism requires for testing to have access to the
> inner labels of the unlock assembly, which are only accessible via the
> debug so.
> 
> Also for general debugging purposes it's convenient to have access to the
> debug vDSO at a well defined place.
> 
> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
> regular 'make vdso_install' layout, including build-id symlinks to find
> the correct file for each process.
> 
> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
> 
> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
> explicit dependency to avoid errors due to concurrent builds.
> 
> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> ---
>  Makefile            | 33 ++++++++++++++++++++++++++++++++-
>  arch/x86/Makefile   |  3 +++
>  init/Kconfig        | 10 ++++++++++
>  kernel/Makefile     |  1 +
>  kernel/vdso_debug.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 89 insertions(+), 1 deletion(-)
> 

This seems to have fallen through the cracks; shall it be considered for
kbuild-7.5?

-- 
Nicolas

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[H. Peter Anvin]

On October 27, 2026 1:22:44 PM PDT, Nicolas Schier <nsc@kernel.org> wrote:
>On 2026-07-08 15:56 +0200, Thomas Weißschuh wrote:
>> Finding the debug version of the vDSO is not trivial as there is no common
>> scheme where it is placed. That's especially problematic for CI testing.
>> 
>> The vDSO futex unlock mechanism requires for testing to have access to the
>> inner labels of the unlock assembly, which are only accessible via the
>> debug so.
>> 
>> Also for general debugging purposes it's convenient to have access to the
>> debug vDSO at a well defined place.
>> 
>> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
>> regular 'make vdso_install' layout, including build-id symlinks to find
>> the correct file for each process.
>> 
>> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
>> 
>> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
>> explicit dependency to avoid errors due to concurrent builds.
>> 
>> Suggested-by: Thomas Gleixner <tglx@kernel.org>
>> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
>> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>> ---
>>  Makefile            | 33 ++++++++++++++++++++++++++++++++-
>>  arch/x86/Makefile   |  3 +++
>>  init/Kconfig        | 10 ++++++++++
>>  kernel/Makefile     |  1 +
>>  kernel/vdso_debug.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>>  5 files changed, 89 insertions(+), 1 deletion(-)
>> 
>
>This seems to have fallen through the cracks; shall it be considered for
>kbuild-7.5?
>

A thought: most tools support compressed separate debug information. Would it make more sense to have the vdso images with separate, compressed debug data in a subdirectory?

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[Thomas Weißschuh]

On Tue, Oct 27, 2026 at 05:02:52PM -0700, H. Peter Anvin wrote:
> On October 27, 2026 1:22:44 PM PDT, Nicolas Schier <nsc@kernel.org> wrote:
> >On 2026-07-08 15:56 +0200, Thomas Weißschuh wrote:
> >> Finding the debug version of the vDSO is not trivial as there is no common
> >> scheme where it is placed. That's especially problematic for CI testing.
> >> 
> >> The vDSO futex unlock mechanism requires for testing to have access to the
> >> inner labels of the unlock assembly, which are only accessible via the
> >> debug so.
> >> 
> >> Also for general debugging purposes it's convenient to have access to the
> >> debug vDSO at a well defined place.
> >> 
> >> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
> >> regular 'make vdso_install' layout, including build-id symlinks to find
> >> the correct file for each process.
> >> 
> >> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
> >> 
> >> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
> >> explicit dependency to avoid errors due to concurrent builds.
> >> 
> >> Suggested-by: Thomas Gleixner <tglx@kernel.org>
> >> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
> >> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
> >> ---
> >>  Makefile            | 33 ++++++++++++++++++++++++++++++++-
> >>  arch/x86/Makefile   |  3 +++
> >>  init/Kconfig        | 10 ++++++++++
> >>  kernel/Makefile     |  1 +
> >>  kernel/vdso_debug.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> >>  5 files changed, 89 insertions(+), 1 deletion(-)
> >> 
> >
> >This seems to have fallen through the cracks; shall it be considered for
> >kbuild-7.5?

Please don't pick this up just yet. I have a prototype which exposes the
directory through sysfs directly without forcing users to unpack the archive.
If you could take a look at the kbuild bits however, that would be great.

> A thought: most tools support compressed separate debug information. Would it
> make more sense to have the vdso images with separate, compressed debug data
> in a subdirectory?

I want to stick to the 'make vdso_install' layout. Maybe that should be
changed to your proposal, too? But what are the specific advantages?
The files are compressed on disk anyways through the module compression.


Thomas

Re: [PATCH] vDSO, kbuild: Provide vDSO debug variants at runtime

[H. Peter Anvin]

On October 27, 2026 10:55:04 PM PDT, "Thomas Weißschuh" <thomas.weissschuh@linutronix.de> wrote:
>On Tue, Oct 27, 2026 at 05:02:52PM -0700, H. Peter Anvin wrote:
>> On October 27, 2026 1:22:44 PM PDT, Nicolas Schier <nsc@kernel.org> wrote:
>> >On 2026-07-08 15:56 +0200, Thomas Weißschuh wrote:
>> >> Finding the debug version of the vDSO is not trivial as there is no common
>> >> scheme where it is placed. That's especially problematic for CI testing.
>> >> 
>> >> The vDSO futex unlock mechanism requires for testing to have access to the
>> >> inner labels of the unlock assembly, which are only accessible via the
>> >> debug so.
>> >> 
>> >> Also for general debugging purposes it's convenient to have access to the
>> >> debug vDSO at a well defined place.
>> >> 
>> >> The files are placed in /sys/kernel/vdso_debug.tar.xz. They use the
>> >> regular 'make vdso_install' layout, including build-id symlinks to find
>> >> the correct file for each process.
>> >> 
>> >> The design is kept close to the ones of the similar IKCONFIG and IKHEADERS.
>> >> 
>> >> On x86 the x32 vDSO is derived from the x86_64 one, necessitating an
>> >> explicit dependency to avoid errors due to concurrent builds.
>> >> 
>> >> Suggested-by: Thomas Gleixner <tglx@kernel.org>
>> >> Link: https://lore.kernel.org/lkml/20260602090536.045586688@kernel.org/
>> >> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
>> >> ---
>> >>  Makefile            | 33 ++++++++++++++++++++++++++++++++-
>> >>  arch/x86/Makefile   |  3 +++
>> >>  init/Kconfig        | 10 ++++++++++
>> >>  kernel/Makefile     |  1 +
>> >>  kernel/vdso_debug.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>> >>  5 files changed, 89 insertions(+), 1 deletion(-)
>> >> 
>> >
>> >This seems to have fallen through the cracks; shall it be considered for
>> >kbuild-7.5?
>
>Please don't pick this up just yet. I have a prototype which exposes the
>directory through sysfs directly without forcing users to unpack the archive.
>If you could take a look at the kbuild bits however, that would be great.
>
>> A thought: most tools support compressed separate debug information. Would it
>> make more sense to have the vdso images with separate, compressed debug data
>> in a subdirectory?
>
>I want to stick to the 'make vdso_install' layout. Maybe that should be
>changed to your proposal, too? But what are the specific advantages?
>The files are compressed on disk anyways through the module compression.
>
>
>Thomas

The nice thing would be that it would let debug tools use them as-is, and after all we need to make the vdso itself available anyway. As a possible side benefit the user would be able to see the post-patch vdso.