Commit 6e803e2e authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon

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: default avatarMark 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: default avatarWill Deacon <will.deacon@arm.com>
parent 5c176aff
......@@ -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
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment