From: Mark Rutland <mark.rutland@arm.com>
To: linux-arm-kernel@lists.infradead.org
Cc: catalin.marinas@arm.com, f.fainelli@gmail.com,
mark.rutland@arm.com, maz@kernel.org, rostedt@goodmis.org,
stefan.wahren@i2se.com, will@kernel.org
Subject: [PATCH] arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE
Date: Mon, 27 Feb 2023 11:58:19 +0000 [thread overview]
Message-ID: <20230227115819.365630-1-mark.rutland@arm.com> (raw)
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(-)
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
--
2.30.2
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next reply other threads:[~2023-02-27 12:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-27 11:58 Mark Rutland [this message]
2023-02-27 19:56 ` [PATCH] arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE Florian Fainelli
2023-02-28 13:54 ` Catalin Marinas
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