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From:   Nathan Chancellor <nathan@kernel.org>
To:     Brian Cain <bcain@codeaurora.org>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        linux-hexagon@vger.kernel.org, linux-kernel@vger.kernel.org,
        clang-built-linux@googlegroups.com,
        Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH 1/3] hexagon: Handle {,SOFT}IRQENTRY_TEXT in linker script
Date:   Thu, 20 May 2021 18:12:37 -0700
Message-Id: <20210521011239.1332345-2-nathan@kernel.org>
In-Reply-To: <20210521011239.1332345-1-nathan@kernel.org>
References: <20210521011239.1332345-1-nathan@kernel.org>
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Patch "mm/slub: use stackdepot to save stack trace in objects" in -mm
selects CONFIG_STACKDEPOT when CONFIG_STACKTRACE_SUPPORT is selected and
CONFIG_STACKDEPOT requires IRQENTRY_TEXT and SOFTIRQENTRY_TEXT to be
handled after commit 505a0ef15f96 ("kasan: stackdepot: move
filter_irq_stacks() to stackdepot.c") due to the use of the
__{,soft}irqentry_text_{start,end} section symbols. If those sections
are not handled, the build is broken.

$ make ARCH=hexagon CROSS_COMPILE=hexagon-linux- LLVM=1 LLVM_IAS=1 defconfig all
...
ld.lld: error: undefined symbol: __irqentry_text_start
>>> referenced by stackdepot.c
>>>               stackdepot.o:(filter_irq_stacks) in archive lib/built-in.a
>>> referenced by stackdepot.c
>>>               stackdepot.o:(filter_irq_stacks) in archive lib/built-in.a

ld.lld: error: undefined symbol: __irqentry_text_end
>>> referenced by stackdepot.c
>>>               stackdepot.o:(filter_irq_stacks) in archive lib/built-in.a
>>> referenced by stackdepot.c
>>>               stackdepot.o:(filter_irq_stacks) in archive lib/built-in.a

ld.lld: error: undefined symbol: __softirqentry_text_start
>>> referenced by stackdepot.c
>>>               stackdepot.o:(filter_irq_stacks) in archive lib/built-in.a
>>> referenced by stackdepot.c
>>>               stackdepot.o:(filter_irq_stacks) in archive lib/built-in.a

ld.lld: error: undefined symbol: __softirqentry_text_end
>>> referenced by stackdepot.c
>>>               stackdepot.o:(filter_irq_stacks) in archive lib/built-in.a
>>> referenced by stackdepot.c
>>>               stackdepot.o:(filter_irq_stacks) in archive lib/built-in.a
...

Add these sections to the Hexagon linker script so the build continues
to work. ld.lld's orphan section warning would have caught this prior to
the -mm commit mentioned above:

ld.lld: warning: kernel/built-in.a(softirq.o):(.softirqentry.text) is being placed in '.softirqentry.text'
ld.lld: warning: kernel/built-in.a(softirq.o):(.softirqentry.text) is being placed in '.softirqentry.text'
ld.lld: warning: kernel/built-in.a(softirq.o):(.softirqentry.text) is being placed in '.softirqentry.text'

Fixes: 505a0ef15f96 ("kasan: stackdepot: move filter_irq_stacks() to stackdepot.c")
Link: https://github.com/ClangBuiltLinux/linux/issues/1381
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/hexagon/kernel/vmlinux.lds.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/hexagon/kernel/vmlinux.lds.S b/arch/hexagon/kernel/vmlinux.lds.S
index 35b18e55eae8..20f19539c5fc 100644
--- a/arch/hexagon/kernel/vmlinux.lds.S
+++ b/arch/hexagon/kernel/vmlinux.lds.S
@@ -38,6 +38,8 @@ SECTIONS
 	.text : AT(ADDR(.text)) {
 		_text = .;
 		TEXT_TEXT
+		IRQENTRY_TEXT
+		SOFTIRQENTRY_TEXT
 		SCHED_TEXT
 		CPUIDLE_TEXT
 		LOCK_TEXT
-- 
2.32.0.rc0