3.18-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 6e803e2e6e367db9a0d6ecae1bd24bb5752011bd ]
The core ftrace code requires that when it is handed the PC of an instrumented function, this PC is the address of the instrumented instruction. This is necessary so that the core ftrace code can identify the specific instrumentation site. Since the instrumented function will be a BL, the address of the instrumented function is LR - 4 at entry to the ftrace code.
This fixup is applied in the mcount_get_pc and mcount_get_pc0 helpers, which acquire the PC of the instrumented function.
The mcount_get_lr helper is used to acquire the LR of the instrumented function, whose value does not require this adjustment, and cannot be adjusted to anything meaningful. No adjustment of this value is made on other architectures, including arm. However, arm64 adjusts this value by 4.
This patch brings arm64 in line with other architectures and removes the adjustment of the LR value.
Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: AKASHI Takahiro takahiro.akashi@linaro.org Cc: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Catalin Marinas catalin.marinas@arm.com Cc: Torsten Duwe duwe@suse.de Cc: Will Deacon will.deacon@arm.com Signed-off-by: Will Deacon will.deacon@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kernel/entry-ftrace.S | 1 - 1 file changed, 1 deletion(-)
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S index c85a02b6cca0..b3fdbba80d4b 100644 --- a/arch/arm64/kernel/entry-ftrace.S +++ b/arch/arm64/kernel/entry-ftrace.S @@ -78,7 +78,6 @@ .macro mcount_get_lr reg ldr \reg, [x29] ldr \reg, [\reg, #8] - mcount_adjust_addr \reg, \reg .endm
.macro mcount_get_lr_addr reg