| Message ID | 20240223064032.3463229-1-swboyd@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: ftrace: Don't forbid CALL_OPS+CC_OPTIMIZE_FOR_SIZE with Clang | expand |
On Thu, Feb 22, 2024 at 10:40:29PM -0800, Stephen Boyd wrote: > Per commit b3f11af9b2ce ("arm64: ftrace: forbid CALL_OPS with > CC_OPTIMIZE_FOR_SIZE"), GCC is silently ignoring `-falign-functions=N` > when passed `-Os`, causing functions to be improperly aligned. This > doesn't seem to be a problem with Clang though, where enabling CALL_OPS > with CC_OPTIMIZE_FOR_SIZE doesn't spit out any warnings at boot about > misaligned patch-sites. Only forbid CALL_OPS if GCC is used and we're > optimizing for size so that CALL_OPS can be used with clang optimizing > for size. > > Cc: Jason Ling <jasonling@chromium.org> > Cc: Florian Fainelli <f.fainelli@gmail.com> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Nathan Chancellor <nathan@kernel.org> > Cc: Nick Desaulniers <ndesaulniers@google.com> > Cc: Bill Wendling <morbo@google.com> > Cc: Justin Stitt <justinstitt@google.com> > Cc: <llvm@lists.linux.dev> > Fixes: b3f11af9b2ce ("arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE") > Signed-off-by: Stephen Boyd <swboyd@chromium.org> Seems reasonable to me. Reviewed-by: Nathan Chancellor <nathan@kernel.org> I wonder if that GCC issue is resolved with '-fmin-function-alignment' that is being introduced in GCC 14 [1]. If it is, I suspect this conditional could actually be CONFIG_CC_HAS_SANE_FUNCTION_ALIGNMENT instead of CONFIG_CC_IS_CLANG, but that can obviously happen as a clean up later down the road (more just food for thought for the arm64 folks, not sure how much '-Os' is used in general) [1]: https://git.kernel.org/masahiroy/linux-kbuild/c/5270316c9fec8cc99aa0e0a258509c5c7f789d12 > --- > arch/arm64/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index aa7c1d435139..6b96d75a3a3d 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -198,7 +198,7 @@ config ARM64 > if DYNAMIC_FTRACE_WITH_ARGS && DYNAMIC_FTRACE_WITH_CALL_OPS > select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS \ > if (DYNAMIC_FTRACE_WITH_ARGS && !CFI_CLANG && \ > - !CC_OPTIMIZE_FOR_SIZE) > + (CC_IS_CLANG || !CC_OPTIMIZE_FOR_SIZE)) > select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \ > if DYNAMIC_FTRACE_WITH_ARGS > select HAVE_SAMPLE_FTRACE_DIRECT > > base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d > -- > https://chromeos.dev >
On Thu, 22 Feb 2024 22:40:29 -0800, Stephen Boyd wrote: > Per commit b3f11af9b2ce ("arm64: ftrace: forbid CALL_OPS with > CC_OPTIMIZE_FOR_SIZE"), GCC is silently ignoring `-falign-functions=N` > when passed `-Os`, causing functions to be improperly aligned. This > doesn't seem to be a problem with Clang though, where enabling CALL_OPS > with CC_OPTIMIZE_FOR_SIZE doesn't spit out any warnings at boot about > misaligned patch-sites. Only forbid CALL_OPS if GCC is used and we're > optimizing for size so that CALL_OPS can be used with clang optimizing > for size. > > [...] Applied to arm64 (for-next/misc), thanks! [1/1] arm64: ftrace: Don't forbid CALL_OPS+CC_OPTIMIZE_FOR_SIZE with Clang https://git.kernel.org/arm64/c/a743f26d03a9
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index aa7c1d435139..6b96d75a3a3d 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -198,7 +198,7 @@ config ARM64 if DYNAMIC_FTRACE_WITH_ARGS && DYNAMIC_FTRACE_WITH_CALL_OPS select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS \ if (DYNAMIC_FTRACE_WITH_ARGS && !CFI_CLANG && \ - !CC_OPTIMIZE_FOR_SIZE) + (CC_IS_CLANG || !CC_OPTIMIZE_FOR_SIZE)) select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \ if DYNAMIC_FTRACE_WITH_ARGS select HAVE_SAMPLE_FTRACE_DIRECT
Per commit b3f11af9b2ce ("arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE"), GCC is silently ignoring `-falign-functions=N` when passed `-Os`, causing functions to be improperly aligned. This doesn't seem to be a problem with Clang though, where enabling CALL_OPS with CC_OPTIMIZE_FOR_SIZE doesn't spit out any warnings at boot about misaligned patch-sites. Only forbid CALL_OPS if GCC is used and we're optimizing for size so that CALL_OPS can be used with clang optimizing for size. Cc: Jason Ling <jasonling@chromium.org> Cc: Florian Fainelli <f.fainelli@gmail.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Bill Wendling <morbo@google.com> Cc: Justin Stitt <justinstitt@google.com> Cc: <llvm@lists.linux.dev> Fixes: b3f11af9b2ce ("arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE") Signed-off-by: Stephen Boyd <swboyd@chromium.org> --- arch/arm64/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) base-commit: 6613476e225e090cc9aad49be7fa504e290dd33d