| Message ID | 20230227115819.365630-1-mark.rutland@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE | expand |
On 2/27/2023 3:58 AM, Mark Rutland wrote: > 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: Catalin Marinas <catalin.marinas@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> Thanks Mark!
On Mon, 27 Feb 2023 11:58:19 +0000, Mark Rutland wrote: > 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. > > [...] Applied to arm64 (for-next/core), thanks! [1/1] arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE https://git.kernel.org/arm64/c/b3f11af9b2ce
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 27b2592698b0..318c61730d44 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -187,7 +187,8 @@ config ARM64 select HAVE_DMA_CONTIGUOUS select HAVE_DYNAMIC_FTRACE 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
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: Catalin Marinas <catalin.marinas@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> --- arch/arm64/Kconfig | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)