* Re: [PATCH] LoongArch: kdump: add arch_crash_save_vmcoreinfo() support
2026-09-23 6:03 [PATCH] LoongArch: kdump: add arch_crash_save_vmcoreinfo() support Yangyang Lian
@ 2026-09-23 6:16 ` sashiko-bot
2026-09-24 2:23 ` Tao Cui
2026-09-24 7:56 ` [PATCH v2] " Yangyang Lian
2 siblings, 0 replies; 5+ messages in thread
From: sashiko-bot @ 2026-09-23 6:16 UTC (permalink / raw)
To: Mike Rapoport, Pratyush Yadav, Huacai Chen, Pasha Tatashin,
Yangyang Lian, Andrew Morton, Baoquan He
Cc: Haoran Jiang, loongarch, WANG Xuerui, George Guo, Dave Young,
kexec, linux-kernel
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] kdump: off-by-one in VMEMMAP_END export causes incorrect range in tools
--
commit 39488158a1b2af61bc47f6be1cf24b8ef1c6d7cd
Author: Yangyang Lian <lianyangyang@kylinos.cn>
LoongArch: kdump: add arch_crash_save_vmcoreinfo() support
This commit implements arch_crash_save_vmcoreinfo() for LoongArch to export
architecture-specific values to the vmcoreinfo PT_NOTE. This allows userspace
crash analysis tools to reliably derive module ranges, vmemmap ranges, VA_BITS,
and the KASLR offset.
> diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
> index 404a15f6782c3..a714ce4cf2141 100644
> --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
> +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
[ ... ]
> +MODULES_VADDR|MODULES_END|VMALLOC_START|VMALLOC_END|VMEMMAP_START|VMEMMAP_END
> +-----------------------------------------------------------------------------
> +
> +Used to get the correct ranges:
> + MODULES_VADDR ~ MODULES_END-1 : Kernel module space.
> + VMALLOC_START ~ VMALLOC_END-1 : vmalloc() / ioremap() space.
> + VMEMMAP_START ~ VMEMMAP_END-1 : vmemmap region, used for struct page array.
[ ... ]
> diff --git a/arch/loongarch/kernel/vmcore_info.c b/arch/loongarch/kernel/vmcore_info.c
> new file mode 100644
> index 0000000000000..1128f6cdfe0dd
> --- /dev/null
> +++ b/arch/loongarch/kernel/vmcore_info.c
[ ... ]
> +void arch_crash_save_vmcoreinfo(void)
> +{
> + VMCOREINFO_NUMBER(VA_BITS);
> + /* NUMBER(VMALLOC_START) is exported by the generic code */
> + vmcoreinfo_append_str("NUMBER(VMALLOC_END)=0x%lx\n", VMALLOC_END);
> +#ifdef CONFIG_64BIT
> + vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n", MODULES_VADDR);
> + vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n", MODULES_END);
> + vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n", (unsigned long)vmemmap);
> + vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n", VMEMMAP_END);
[Severity: Medium]
Is this exporting the correct boundary for VMEMMAP_END?
As documented in the newly added admin-guide for vmcoreinfo (above), tools
like crash or makedumpfile expect the exported VMEMMAP_END to act as an
exclusive bound (VMEMMAP_START ~ VMEMMAP_END-1).
However, on LoongArch, the VMEMMAP_END macro is defined as an inclusive bound.
Exporting it directly without adjusting it to an exclusive bound
(e.g., VMEMMAP_END + 1) means the exported value is off by one byte.
Could this cause tools calculating the size via VMEMMAP_END - VMEMMAP_START
to get VMEMMAP_SIZE - 1, thereby truncating the last page when shifted and
triggering errors when analyzing the vmcore?
> +#endif
> + vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%lx\n", PHYS_OFFSET);
> + vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
> +}
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260923060349.146780-1-lianyangyang@kylinos.cn?part=1
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] LoongArch: kdump: add arch_crash_save_vmcoreinfo() support
2026-09-23 6:03 [PATCH] LoongArch: kdump: add arch_crash_save_vmcoreinfo() support Yangyang Lian
2026-09-23 6:16 ` sashiko-bot
@ 2026-09-24 2:23 ` Tao Cui
2026-09-24 7:56 ` [PATCH v2] " Yangyang Lian
2 siblings, 0 replies; 5+ messages in thread
From: Tao Cui @ 2026-09-24 2:23 UTC (permalink / raw)
To: Yangyang Lian, Andrew Morton, Baoquan He, Mike Rapoport,
Pasha Tatashin, Pratyush Yadav, Huacai Chen
Cc: cui.tao, Dave Young, WANG Xuerui, kexec, loongarch, linux-kernel,
Haoran Jiang, George Guo
Hi Yangyang,
在 2026/9/23 14:03, Yangyang Lian 写道:
> Since commit 23c85094fe18 ("proc/kcore: add vmcoreinfo note to
> /proc/kcore") the kernel has exported the vmcoreinfo PT_NOTE on
> /proc/kcore as wellas /proc/vmcore.
>
> LoongArch does not provide arch_crash_save_vmcoreinfo(), so the
> arch-specific values are missing from the vmcoreinfo PT_NOTE. The
> generic exporter in kernel/vmcore_info.c already provides
> NUMBER(VMALLOC_START), but tools like crash cannot derive the module
> and vmemmap ranges, VA_BITS, or the KASLR offset of a LoongArch dump.
>
> Since commit 18210a104bb9 ("LoongArch: Expand module virtual address
> space to 2GB") the vmalloc and module boundaries are no longer stable
> across kernel versions either, so vmcoreinfo is the only reliable
> source for them.
>
I gave this patch a run on a Loongson-3A6000 box: built next-20260922
with it applied and booted the kernel as a KVM guest. Without the
patch /proc/kcore only has the generic fields (OSRELEASE, PAGESIZE,
NUMBER(VMALLOC_START) and the usual symbols/offsets). With it, the
note now looks like:
OSRELEASE=7.3.0-rc4-next-20260922-eagersplit+
PAGESIZE=16384
NUMBER(VMALLOC_START)=0xffff800082008000
NUMBER(VA_BITS)=47
NUMBER(VMALLOC_END)=0xfffffebffd7f8000
NUMBER(MODULES_VADDR)=0xffff800002008000
NUMBER(MODULES_END)=0xffff800082008000
NUMBER(VMEMMAP_START)=0xfffffebffe000000
NUMBER(VMEMMAP_END)=0xfffffffffdffffff
NUMBER(PHYS_OFFSET)=0x0
KERNELOFFSET=0
(KASLR is off in my guest cmdline, hence KERNELOFFSET=0.)
One thing worth a look: as also pointed out in the sashiko review,
VMEMMAP_END on LoongArch is an inclusive bound (note the ...fdffffff
above), while the doc added in this patch says
VMEMMAP_START ~ VMEMMAP_END-1, and tools like makedumpfile compute
the size as VMEMMAP_END - VMEMMAP_START. So exporting VMEMMAP_END + 1
would probably match what consumers expect.
Works fine otherwise.
Tested-by: Tao Cui <cuitao@kylinos.cn>
> Provide this function in a separate file that is built at the same time
> as its caller in kernel/vmcore_info.c, and add a LOONGARCH64 section to
> Documentation/admin-guide/kdump/vmcoreinfo.rst.
>
> Reported-by: Haoran Jiang <jianghaoran@kylinos.cn>
> Suggested-by: Haoran Jiang <jianghaoran@kylinos.cn>
> Co-developed-by: George Guo <guodongtai@kylinos.cn>
> Signed-off-by: George Guo <guodongtai@kylinos.cn>
> Signed-off-by: Yangyang Lian <lianyangyang@kylinos.cn>
> ---
> .../admin-guide/kdump/vmcoreinfo.rst | 29 +++++++++++++++++++
> arch/loongarch/kernel/Makefile | 1 +
> arch/loongarch/kernel/vmcore_info.c | 21 ++++++++++++++
> 3 files changed, 51 insertions(+)
> create mode 100644 arch/loongarch/kernel/vmcore_info.c
>
> diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
> index 7663c610fe90..2ff921232616 100644
> --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
> +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
> @@ -594,3 +594,32 @@ va_kernel_pa_offset
>
> Indicates the offset between the kernel virtual and physical mappings.
> Used to translate virtual to physical addresses.
> +
> +LOONGARCH64
> +===========
> +
> +VA_BITS
> +-------
> +
> +The maximum number of bits for virtual addresses. Used to compute the
> +virtual memory ranges.
> +
> +PHYS_OFFSET
> +-----------
> +
> +Indicates the physical address of the start of memory. Used to translate
> +virtual to physical addresses.
> +
> +KERNELOFFSET
> +------------
> +
> +The kernel randomization offset. Used to locate the kernel text in
> +virtual memory. If KASLR is disabled, this value is zero.
> +
> +MODULES_VADDR|MODULES_END|VMALLOC_START|VMALLOC_END|VMEMMAP_START|VMEMMAP_END
> +-----------------------------------------------------------------------------
> +
> +Used to get the correct ranges:
> + MODULES_VADDR ~ MODULES_END-1 : Kernel module space.
> + VMALLOC_START ~ VMALLOC_END-1 : vmalloc() / ioremap() space.
> + VMEMMAP_START ~ VMEMMAP_END-1 : vmemmap region, used for struct page array.
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 001924877772..6260c15adaba 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -64,6 +64,7 @@ obj-$(CONFIG_RELOCATABLE) += relocate.o
> obj-$(CONFIG_KEXEC_CORE) += machine_kexec.o relocate_kernel.o
> obj-$(CONFIG_KEXEC_FILE) += machine_kexec_file.o kexec_efi.o kexec_elf.o
> obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
> +obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o
>
> obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o
> obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o
> diff --git a/arch/loongarch/kernel/vmcore_info.c b/arch/loongarch/kernel/vmcore_info.c
> new file mode 100644
> index 000000000000..1128f6cdfe0d
> --- /dev/null
> +++ b/arch/loongarch/kernel/vmcore_info.c
> @@ -0,0 +1,21 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/vmcore_info.h>
> +#include <asm/addrspace.h>
> +#include <asm/pgtable.h>
> +#include <asm/setup.h>
> +
> +void arch_crash_save_vmcoreinfo(void)
> +{
> + VMCOREINFO_NUMBER(VA_BITS);
> + /* NUMBER(VMALLOC_START) is exported by the generic code */
> + vmcoreinfo_append_str("NUMBER(VMALLOC_END)=0x%lx\n", VMALLOC_END);
> +#ifdef CONFIG_64BIT
> + vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n", MODULES_VADDR);
> + vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n", MODULES_END);
> + vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n", (unsigned long)vmemmap);
> + vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n", VMEMMAP_END);
> +#endif
> + vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%lx\n", PHYS_OFFSET);
> + vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
> +}
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH v2] LoongArch: kdump: add arch_crash_save_vmcoreinfo() support
2026-09-23 6:03 [PATCH] LoongArch: kdump: add arch_crash_save_vmcoreinfo() support Yangyang Lian
2026-09-23 6:16 ` sashiko-bot
2026-09-24 2:23 ` Tao Cui
@ 2026-09-24 7:56 ` Yangyang Lian
2026-09-24 8:04 ` sashiko-bot
2 siblings, 1 reply; 5+ messages in thread
From: Yangyang Lian @ 2026-09-24 7:56 UTC (permalink / raw)
To: Andrew Morton, Baoquan He, Mike Rapoport, Pasha Tatashin,
Pratyush Yadav, Huacai Chen
Cc: Dave Young, WANG Xuerui, kexec, loongarch, linux-kernel,
Yangyang Lian, Haoran Jiang, Tao Cui, George Guo
Since commit 23c85094fe18 ("proc/kcore: add vmcoreinfo note to
/proc/kcore") the kernel has exported the vmcoreinfo PT_NOTE on
/proc/kcore as wellas /proc/vmcore.
LoongArch does not provide arch_crash_save_vmcoreinfo(), so the
arch-specific values are missing from the vmcoreinfo PT_NOTE. The
generic exporter in kernel/vmcore_info.c already provides
NUMBER(VMALLOC_START), but tools like crash cannot derive the module
and vmemmap ranges, VA_BITS, or the KASLR offset of a LoongArch dump.
Since commit 18210a104bb9 ("LoongArch: Expand module virtual address
space to 2GB") the vmalloc and module boundaries are no longer stable
across kernel versions either, so vmcoreinfo is the only reliable
source for them.
Provide this function in a separate file that is built at the same time
as its caller in kernel/vmcore_info.c, and add a LOONGARCH64 section to
Documentation/admin-guide/kdump/vmcoreinfo.rst.
Reported-by: Haoran Jiang <jianghaoran@kylinos.cn>
Suggested-by: Haoran Jiang <jianghaoran@kylinos.cn>
Tested-by: Tao Cui <cuitao@kylinos.cn>
Co-developed-by: George Guo <guodongtai@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
Signed-off-by: Yangyang Lian <lianyangyang@kylinos.cn>
---
V2 -> V1: Export VMEMMAP_END + 1 to make it an exclusive bound, matching
what tools like makedumpfile expect.
Add Tested-by tag from Tao Cui.
.../admin-guide/kdump/vmcoreinfo.rst | 29 +++++++++++++++++++
arch/loongarch/kernel/Makefile | 1 +
arch/loongarch/kernel/vmcore_info.c | 21 ++++++++++++++
3 files changed, 51 insertions(+)
create mode 100644 arch/loongarch/kernel/vmcore_info.c
diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
index 7663c610fe90..2ff921232616 100644
--- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
+++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
@@ -594,3 +594,32 @@ va_kernel_pa_offset
Indicates the offset between the kernel virtual and physical mappings.
Used to translate virtual to physical addresses.
+
+LOONGARCH64
+===========
+
+VA_BITS
+-------
+
+The maximum number of bits for virtual addresses. Used to compute the
+virtual memory ranges.
+
+PHYS_OFFSET
+-----------
+
+Indicates the physical address of the start of memory. Used to translate
+virtual to physical addresses.
+
+KERNELOFFSET
+------------
+
+The kernel randomization offset. Used to locate the kernel text in
+virtual memory. If KASLR is disabled, this value is zero.
+
+MODULES_VADDR|MODULES_END|VMALLOC_START|VMALLOC_END|VMEMMAP_START|VMEMMAP_END
+-----------------------------------------------------------------------------
+
+Used to get the correct ranges:
+ MODULES_VADDR ~ MODULES_END-1 : Kernel module space.
+ VMALLOC_START ~ VMALLOC_END-1 : vmalloc() / ioremap() space.
+ VMEMMAP_START ~ VMEMMAP_END-1 : vmemmap region, used for struct page array.
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 001924877772..6260c15adaba 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -64,6 +64,7 @@ obj-$(CONFIG_RELOCATABLE) += relocate.o
obj-$(CONFIG_KEXEC_CORE) += machine_kexec.o relocate_kernel.o
obj-$(CONFIG_KEXEC_FILE) += machine_kexec_file.o kexec_efi.o kexec_elf.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
+obj-$(CONFIG_VMCORE_INFO) += vmcore_info.o
obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o
obj-$(CONFIG_UNWINDER_PROLOGUE) += unwind_prologue.o
diff --git a/arch/loongarch/kernel/vmcore_info.c b/arch/loongarch/kernel/vmcore_info.c
new file mode 100644
index 000000000000..fb703b716253
--- /dev/null
+++ b/arch/loongarch/kernel/vmcore_info.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/vmcore_info.h>
+#include <asm/addrspace.h>
+#include <asm/pgtable.h>
+#include <asm/setup.h>
+
+void arch_crash_save_vmcoreinfo(void)
+{
+ VMCOREINFO_NUMBER(VA_BITS);
+ /* NUMBER(VMALLOC_START) is exported by the generic code */
+ vmcoreinfo_append_str("NUMBER(VMALLOC_END)=0x%lx\n", VMALLOC_END);
+#ifdef CONFIG_64BIT
+ vmcoreinfo_append_str("NUMBER(MODULES_VADDR)=0x%lx\n", MODULES_VADDR);
+ vmcoreinfo_append_str("NUMBER(MODULES_END)=0x%lx\n", MODULES_END);
+ vmcoreinfo_append_str("NUMBER(VMEMMAP_START)=0x%lx\n", (unsigned long)vmemmap);
+ vmcoreinfo_append_str("NUMBER(VMEMMAP_END)=0x%lx\n", VMEMMAP_END + 1);
+#endif
+ vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%lx\n", PHYS_OFFSET);
+ vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
+}
--
2.25.1
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH v2] LoongArch: kdump: add arch_crash_save_vmcoreinfo() support
2026-09-24 7:56 ` [PATCH v2] " Yangyang Lian
@ 2026-09-24 8:04 ` sashiko-bot
0 siblings, 0 replies; 5+ messages in thread
From: sashiko-bot @ 2026-09-24 8:04 UTC (permalink / raw)
To: Yangyang Lian, Andrew Morton, Pratyush Yadav, Pasha Tatashin,
Huacai Chen, Mike Rapoport, Baoquan He
Cc: WANG Xuerui, Tao Cui, Dave Young, George Guo, kexec, loongarch,
Haoran Jiang, linux-kernel
> Since commit 23c85094fe18 ("proc/kcore: add vmcoreinfo note to
> /proc/kcore") the kernel has exported the vmcoreinfo PT_NOTE on
> /proc/kcore as wellas /proc/vmcore.
>
> LoongArch does not provide arch_crash_save_vmcoreinfo(), so the
> arch-specific values are missing from the vmcoreinfo PT_NOTE. The
> generic exporter in kernel/vmcore_info.c already provides
> NUMBER(VMALLOC_START), but tools like crash cannot derive the module
> and vmemmap ranges, VA_BITS, or the KASLR offset of a LoongArch dump.
>
> Since commit 18210a104bb9 ("LoongArch: Expand module virtual address
> space to 2GB") the vmalloc and module boundaries are no longer stable
> across kernel versions either, so vmcoreinfo is the only reliable
> source for them.
>
> Provide this function in a separate file that is built at the same time
> as its caller in kernel/vmcore_info.c, and add a LOONGARCH64 section to
> Documentation/admin-guide/kdump/vmcoreinfo.rst.
>
> Reported-by: Haoran Jiang <jianghaoran@kylinos.cn>
> Suggested-by: Haoran Jiang <jianghaoran@kylinos.cn>
> Tested-by: Tao Cui <cuitao@kylinos.cn>
> Co-developed-by: George Guo <guodongtai@kylinos.cn>
> Signed-off-by: George Guo <guodongtai@kylinos.cn>
> Signed-off-by: Yangyang Lian <lianyangyang@kylinos.cn>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260924075655.375632-1-lianyangyang@kylinos.cn?part=1
^ permalink raw reply [flat|nested] 5+ messages in thread