| Message ID | 20240925175021.1526936-2-Jason@zx2c4.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 4b058c9f281f5b100efbf665dd5a1a05e1654d6d |
| Headers | show |
| Series | powerpc/vdso: allow r30 in vDSO code generation of getrandom | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 8 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 21 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 5 jobs. |
On Wed, Sep 25, 2024 at 07:50:22PM +0200, Jason A. Donenfeld wrote: > For gettimeofday, -ffixed-r30 was passed to work around a bug in Go > code, where the vDSO trampoline forgot to save and restore this register > across function calls. But Go requires a different trampoline for every > call, and there's no reason that new Go code needs to be broken and add > more bugs. So remove -ffixed-r30 for getrandom. Strangely, I am _unable to_ make the Go code not crash with this patch applied. I'm not quite sure what I'm doing wrong yet, or if this points to another issue.
Le 25/09/2024 à 20:38, Jason A. Donenfeld a écrit : > On Wed, Sep 25, 2024 at 07:50:22PM +0200, Jason A. Donenfeld wrote: >> For gettimeofday, -ffixed-r30 was passed to work around a bug in Go >> code, where the vDSO trampoline forgot to save and restore this register >> across function calls. But Go requires a different trampoline for every >> call, and there's no reason that new Go code needs to be broken and add >> more bugs. So remove -ffixed-r30 for getrandom. > > Strangely, I am _unable to_ make the Go code not crash with this patch > applied. I'm not quite sure what I'm doing wrong yet, or if this points > to another issue. Do you mean that without this patch the Go code works and with this patch it crashes ? That's strange taken into account that the chacha function plays up with r30 regardless of this patch. Christophe
On Wed, Sep 25, 2024 at 08:48:31PM +0200, Christophe Leroy wrote: > > > Le 25/09/2024 à 20:38, Jason A. Donenfeld a écrit : > > On Wed, Sep 25, 2024 at 07:50:22PM +0200, Jason A. Donenfeld wrote: > >> For gettimeofday, -ffixed-r30 was passed to work around a bug in Go > >> code, where the vDSO trampoline forgot to save and restore this register > >> across function calls. But Go requires a different trampoline for every > >> call, and there's no reason that new Go code needs to be broken and add > >> more bugs. So remove -ffixed-r30 for getrandom. > > > > Strangely, I am _unable to_ make the Go code not crash with this patch > > applied. I'm not quite sure what I'm doing wrong yet, or if this points > > to another issue. > > Do you mean that without this patch the Go code works and with this > patch it crashes ? That's strange taken into account that the chacha > function plays up with r30 regardless of this patch. Yea, that's what I meant. It turned out to be a Go runtime bug, which won't affect other vDSO functions but does affect getrandom(). I fixed the issue and sent a patch up to Google. So this is not the kernel's issue. Therefore, this patch can move forward. Jason
On Wed, 25 Sep 2024 19:50:22 +0200, Jason A. Donenfeld wrote: > For gettimeofday, -ffixed-r30 was passed to work around a bug in Go > code, where the vDSO trampoline forgot to save and restore this register > across function calls. But Go requires a different trampoline for every > call, and there's no reason that new Go code needs to be broken and add > more bugs. So remove -ffixed-r30 for getrandom. > > > [...] Applied to powerpc/fixes. [1/1] powerpc/vdso: allow r30 in vDSO code generation of getrandom https://git.kernel.org/powerpc/c/4b058c9f281f5b100efbf665dd5a1a05e1654d6d cheers
diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile index 56fb1633529a..31ca5a547004 100644 --- a/arch/powerpc/kernel/vdso/Makefile +++ b/arch/powerpc/kernel/vdso/Makefile @@ -22,7 +22,7 @@ endif ifneq ($(c-getrandom-y),) CFLAGS_vgetrandom-32.o += -include $(c-getrandom-y) - CFLAGS_vgetrandom-64.o += -include $(c-getrandom-y) $(call cc-option, -ffixed-r30) + CFLAGS_vgetrandom-64.o += -include $(c-getrandom-y) endif # Build rules
For gettimeofday, -ffixed-r30 was passed to work around a bug in Go code, where the vDSO trampoline forgot to save and restore this register across function calls. But Go requires a different trampoline for every call, and there's no reason that new Go code needs to be broken and add more bugs. So remove -ffixed-r30 for getrandom. Fixes: 8072b39c3a75 ("powerpc/vdso: Wire up getrandom() vDSO implementation on VDSO64") Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- Michael - can you take this through your tree as a ppc fix? arch/powerpc/kernel/vdso/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)