From b3f11af9b2ce14d4662753d097a21e1d37a06fda Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Mon, 27 Feb 2023 11:58:19 +0000 Subject: [PATCH] arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE 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 Link: http://lore.kernel.org/linux-arm-kernel/2d9284c3-3805-402b-5423-520ced56d047@gmail.com Signed-off-by: Mark Rutland Cc: Marc Zyngier Cc: Stefan Wahren Cc: Steven Rostedt Cc: Will Deacon Tested-by: Florian Fainelli Link: https://lore.kernel.org/r/20230227115819.365630-1-mark.rutland@arm.com Signed-off-by: Catalin Marinas --- arch/arm64/Kconfig | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 71c35178e017..f7521695a474 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -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