linux-kernel - [PATCH 6.8 494/715] arm64: ftrace: Don't forbid CALL_OPS+CC_OPTIMIZE_FOR

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Date: Sun, 24 Mar 2024 18:31:13 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Stephen Boyd <swboyd@...omium.org>,
	Jason Ling <jasonling@...omium.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	llvm@...ts.linux.dev,
	Catalin Marinas <catalin.marinas@....com>,
	Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.8 494/715] arm64: ftrace: Don't forbid CALL_OPS+CC_OPTIMIZE_FOR_SIZE with Clang

From: Stephen Boyd <swboyd@...omium.org>

[ Upstream commit a743f26d03a96593c0f3d05dc26b388f45de67c9 ]

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@...omium.org>
Cc: Florian Fainelli <f.fainelli@...il.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Bill Wendling <morbo@...gle.com>
Cc: Justin Stitt <justinstitt@...gle.com>
Cc: llvm@...ts.linux.dev
Fixes: b3f11af9b2ce ("arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE")
Signed-off-by: Stephen Boyd <swboyd@...omium.org>
Reviewed-by: Nathan Chancellor <nathan@...nel.org>
Link: https://lore.kernel.org/r/20240223064032.3463229-1-swboyd@chromium.org
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/arm64/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index aa7c1d4351396..6b96d75a3a3d8 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
-- 
2.43.0