[PATCH v3 0/2] Prevent dynamic relocations in vDSO

[PATCH v3 0/2] Prevent dynamic relocations in vDSO

[Alexandre Ghiti]

Patch 2 uses a generic function to make sure the vDSO object does not
contain any dynamic relocations.

Patch 1 removes a dynamic relocation from vDSO in rv32 found with patch
2.

v2: https://lore.kernel.org/linux-riscv/20240705060902.113294-1-alexghiti@rivosinc.com/
v1: https://lore.kernel.org/linux-riscv/20240326113831.283025-1-alexghiti@rivosinc.com/

Changes in v3:
- Add RB and TB from Bjorn and Vladimir from v1
- Use -fno-builtin instead of the previous option that does not exist in llvm
  (Palmer)

Changes in v2:
- Add patch 1 (Björn)

Alexandre Ghiti (2):
  riscv: vdso: Prevent the compiler from inserting calls to memset()
  riscv: Check that vdso does not contain any dynamic relocations

 arch/riscv/kernel/vdso/Makefile | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

-- 
2.39.2

[PATCH v3 1/2] riscv: vdso: Prevent the compiler from inserting calls to memset()

[Alexandre Ghiti]

The compiler is smart enough to insert a call to memset() in
riscv_vdso_get_cpus(), which generates a dynamic relocation.

So prevent this by using -fno-builtin option.

Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API")
Cc: stable@vger.kernel.org
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
---
 arch/riscv/kernel/vdso/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
index 960feb1526ca..3f1c4b2d0b06 100644
--- a/arch/riscv/kernel/vdso/Makefile
+++ b/arch/riscv/kernel/vdso/Makefile
@@ -18,6 +18,7 @@ obj-vdso = $(patsubst %, %.o, $(vdso-syms)) note.o
 
 ccflags-y := -fno-stack-protector
 ccflags-y += -DDISABLE_BRANCH_PROFILING
+ccflags-y += -fno-builtin
 
 ifneq ($(c-gettimeofday-y),)
   CFLAGS_vgettimeofday.o += -fPIC -include $(c-gettimeofday-y)
-- 
2.39.2

Re: [PATCH v3 1/2] riscv: vdso: Prevent the compiler from inserting calls to memset()

[Guo Ren]

On Wed, Oct 16, 2024 at 4:37 PM Alexandre Ghiti <alexghiti@rivosinc.com> wrote:
>
> The compiler is smart enough to insert a call to memset() in
> riscv_vdso_get_cpus(), which generates a dynamic relocation.
>
> So prevent this by using -fno-builtin option.
>
> Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> ---
>  arch/riscv/kernel/vdso/Makefile | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> index 960feb1526ca..3f1c4b2d0b06 100644
> --- a/arch/riscv/kernel/vdso/Makefile
> +++ b/arch/riscv/kernel/vdso/Makefile
> @@ -18,6 +18,7 @@ obj-vdso = $(patsubst %, %.o, $(vdso-syms)) note.o
>
>  ccflags-y := -fno-stack-protector
>  ccflags-y += -DDISABLE_BRANCH_PROFILING
> +ccflags-y += -fno-builtin
LGTM!
Reviewed-by: Guo Ren <guoren@kernel.org>

>
>  ifneq ($(c-gettimeofday-y),)
>    CFLAGS_vgettimeofday.o += -fPIC -include $(c-gettimeofday-y)
> --
> 2.39.2
>


-- 
Best Regards
 Guo Ren

[PATCH v3 2/2] riscv: Check that vdso does not contain any dynamic relocations

[Alexandre Ghiti]

Like other architectures, use the common cmd_vdso_check to make sure of
that.

Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Tested-by: Vladimir Isaev <vladimir.isaev@syntacore.com>
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
---
 arch/riscv/kernel/vdso/Makefile | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
index 3f1c4b2d0b06..9a1b555e8733 100644
--- a/arch/riscv/kernel/vdso/Makefile
+++ b/arch/riscv/kernel/vdso/Makefile
@@ -45,7 +45,7 @@ $(obj)/vdso.o: $(obj)/vdso.so
 
 # link rule for the .so file, .lds has to be first
 $(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
-	$(call if_changed,vdsold)
+	$(call if_changed,vdsold_and_check)
 LDFLAGS_vdso.so.dbg = -shared -soname=linux-vdso.so.1 \
 	--build-id=sha1 --hash-style=both --eh-frame-hdr
 
@@ -65,7 +65,8 @@ include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
 # actual build commands
 # The DSO images are built using a special linker script
 # Make sure only to export the intended __vdso_xxx symbol offsets.
-quiet_cmd_vdsold = VDSOLD  $@
-      cmd_vdsold = $(LD) $(ld_flags) -T $(filter-out FORCE,$^) -o $@.tmp && \
+quiet_cmd_vdsold_and_check = VDSOLD  $@
+      cmd_vdsold_and_check = $(LD) $(ld_flags) -T $(filter-out FORCE,$^) -o $@.tmp && \
                    $(OBJCOPY) $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \
-                   rm $@.tmp
+                   rm $@.tmp && \
+                   $(cmd_vdso_check)
-- 
2.39.2

Re: [PATCH v3 2/2] riscv: Check that vdso does not contain any dynamic relocations

[Guo Ren]

On Wed, Oct 16, 2024 at 4:38 PM Alexandre Ghiti <alexghiti@rivosinc.com> wrote:
>
> Like other architectures, use the common cmd_vdso_check to make sure of
> that.
>
> Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
> Tested-by: Vladimir Isaev <vladimir.isaev@syntacore.com>
> Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
> ---
>  arch/riscv/kernel/vdso/Makefile | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/kernel/vdso/Makefile b/arch/riscv/kernel/vdso/Makefile
> index 3f1c4b2d0b06..9a1b555e8733 100644
> --- a/arch/riscv/kernel/vdso/Makefile
> +++ b/arch/riscv/kernel/vdso/Makefile
> @@ -45,7 +45,7 @@ $(obj)/vdso.o: $(obj)/vdso.so
>
>  # link rule for the .so file, .lds has to be first
>  $(obj)/vdso.so.dbg: $(obj)/vdso.lds $(obj-vdso) FORCE
> -       $(call if_changed,vdsold)
> +       $(call if_changed,vdsold_and_check)
>  LDFLAGS_vdso.so.dbg = -shared -soname=linux-vdso.so.1 \
>         --build-id=sha1 --hash-style=both --eh-frame-hdr
>
> @@ -65,7 +65,8 @@ include/generated/vdso-offsets.h: $(obj)/vdso.so.dbg FORCE
>  # actual build commands
>  # The DSO images are built using a special linker script
>  # Make sure only to export the intended __vdso_xxx symbol offsets.
> -quiet_cmd_vdsold = VDSOLD  $@
> -      cmd_vdsold = $(LD) $(ld_flags) -T $(filter-out FORCE,$^) -o $@.tmp && \
> +quiet_cmd_vdsold_and_check = VDSOLD  $@
> +      cmd_vdsold_and_check = $(LD) $(ld_flags) -T $(filter-out FORCE,$^) -o $@.tmp && \
>                     $(OBJCOPY) $(patsubst %, -G __vdso_%, $(vdso-syms)) $@.tmp $@ && \
> -                   rm $@.tmp
> +                   rm $@.tmp && \
> +                   $(cmd_vdso_check)
Following other architectures to append a $(cmd_vdso_check) is okay.

Reviewed-by: Guo Ren <guoren@kernel.org>

> --
> 2.39.2
>


-- 
Best Regards
 Guo Ren

Re: [PATCH v3 0/2] Prevent dynamic relocations in vDSO

[patchwork-bot+linux-riscv]

Hello:

This series was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Wed, 16 Oct 2024 10:36:23 +0200 you wrote:
> Patch 2 uses a generic function to make sure the vDSO object does not
> contain any dynamic relocations.
> 
> Patch 1 removes a dynamic relocation from vDSO in rv32 found with patch
> 2.
> 
> v2: https://lore.kernel.org/linux-riscv/20240705060902.113294-1-alexghiti@rivosinc.com/
> v1: https://lore.kernel.org/linux-riscv/20240326113831.283025-1-alexghiti@rivosinc.com/
> 
> [...]

Here is the summary with links:
  - [v3,1/2] riscv: vdso: Prevent the compiler from inserting calls to memset()
    https://git.kernel.org/riscv/c/f431f67ff6c2
  - [v3,2/2] riscv: Check that vdso does not contain any dynamic relocations
    https://git.kernel.org/riscv/c/fcb5dcb789a2

You are awesome, thank you!
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