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arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE

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Florian reports that when building with CONFIG_CC_OPTIMIZE_FOR_SIZE=y,
he sees "Misaligned patch-site" warnings at boot, e.g.

| Misaligned patch-site bcm2836_arm_irqchip_handle_irq+0x0/0x88
| WARNING: CPU: 0 PID: 0 at arch/arm64/kernel/ftrace.c:120 ftrace_call_adjust+0x4c/0x70

This is because GCC will silently ignore `-falign-functions=N` when
passed `-Os`, resulting in functions not being aligned as we expect.
This is a known issue, and to account for this we modified the kernel to
avoid `-Os` generally. Unfortunately we forgot to account for
CONFIG_CC_OPTIMIZE_FOR_SIZE.

Forbid the use of CALL_OPS with CONFIG_CC_OPTIMIZE_FOR_SIZE=y to prevent
this issue. All exising ftrace features will work as before, though
without the performance benefit of CALL_OPS.

Reported-by: Florian Fainelli <f.fainelli@gmail.com>
Link: http://lore.kernel.org/linux-arm-kernel/2d9284c3-3805-402b-5423-520ced56d047@gmail.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Stefan Wahren <stefan.wahren@i2se.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Deacon <will@kernel.org>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230227115819.365630-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Rutland 2023-02-27 11:58:19 +00:00 committed by Catalin Marinas
parent 1b561d3949
commit b3f11af9b2
1 changed files with 2 additions and 1 deletions
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3
arch/arm64/Kconfig
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@ -188,7 +188,8 @@ config ARM64
select HAVE_DYNAMIC_FTRACE_WITH_ARGS \
if $(cc-option,-fpatchable-function-entry=2)
select HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS \
if (DYNAMIC_FTRACE_WITH_ARGS && !CFI_CLANG)
if (DYNAMIC_FTRACE_WITH_ARGS && !CFI_CLANG && \
!CC_OPTIMIZE_FOR_SIZE)
select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \
if DYNAMIC_FTRACE_WITH_ARGS
select HAVE_EFFICIENT_UNALIGNED_ACCESS