From 2d6f9a86cd9a6081e0431f19757cc0879a701775 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Thu, 15 Nov 2018 22:42:01 +0000 Subject: [PATCH] arm64: ftrace: don't adjust the LR value [ 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 Cc: AKASHI Takahiro Cc: Ard Biesheuvel Cc: Catalin Marinas Cc: Torsten Duwe Cc: Will Deacon Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- 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 0f03a8fe2314..d18d15810d19 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