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Subject[PATCH 3/8] arm64: Extend support for CONFIG_FUNCTION_ALIGNMENT
Date
On arm64 we don't align assembly funciton in the same way as C
functions. This somewhat limits the utility of
CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B for testing.

Follow the example of x86, and align assembly functions in the same way
as C functions.

I've tested this by selecting CONFIG_DEBUG_FORCE_FUNCTION_ALIGN_64B=y,
building and booting a kernel, and looking for misaligned text symbols:

Before:
# grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | wc -l
322

After:
# grep ' [Tt] ' /proc/kallsyms | grep -iv '[048c]0 [Tt] ' | wc -l
115

The remaining unaligned text symbols are a combination of non-function labels
in assembly and early position-independent code which is built with '-Os'.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/linkage.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/linkage.h b/arch/arm64/include/asm/linkage.h
index 1436fa1cde24d..df18a3446ce82 100644
--- a/arch/arm64/include/asm/linkage.h
+++ b/arch/arm64/include/asm/linkage.h
@@ -5,8 +5,14 @@
#include <asm/assembler.h>
#endif

-#define __ALIGN .align 2
-#define __ALIGN_STR ".align 2"
+#if CONFIG_FUNCTION_ALIGNMENT > 0
+#define ARM64_FUNCTION_ALIGNMENT CONFIG_FUNCTION_ALIGNMENT
+#else
+#define ARM64_FUNCTION_ALIGNMENT 4
+#endif
+
+#define __ALIGN .balign ARM64_FUNCTION_ALIGNMENT
+#define __ALIGN_STR ".balign " #ARM64_FUNCTION_ALIGNMENT

/*
* When using in-kernel BTI we need to ensure that PCS-conformant
--
2.30.2
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