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authorMark Rutland <mark.rutland@arm.com>2018-11-15 22:42:01 +0000
committerWill Deacon <will.deacon@arm.com>2018-11-30 13:29:05 +0000
commit6e803e2e6e367db9a0d6ecae1bd24bb5752011bd (patch)
treeaebd74d5cc755fad5e08ad449c38a1055aa57bd6 /arch
parent5c176aff5b5a7027840c37da9d48a8f9cedb08b9 (diff)
downloadlinux-6e803e2e6e367db9a0d6ecae1bd24bb5752011bd.tar.bz2
arm64: ftrace: don't adjust the LR value
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/kernel/entry-ftrace.S1
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index bb549f71948d..bc1ccd253007 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -79,7 +79,6 @@
.macro mcount_get_lr reg
ldr \reg, [x29]
ldr \reg, [\reg, #8]
- mcount_adjust_addr \reg, \reg
.endm
.macro mcount_get_lr_addr reg