linux-kernel - [PATCH v2 2/6] arm64: entry: add unwind info for various kernel entries

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Message-ID: <20250904223850.884188-3-dylanbhatch@google.com>
Date: Thu,  4 Sep 2025 22:38:46 +0000
From: Dylan Hatch <dylanbhatch@...gle.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Indu Bhagat <indu.bhagat@...cle.com>, Peter Zijlstra <peterz@...radead.org>, 
	Will Deacon <will@...nel.org>, Catalin Marinas <catalin.marinas@....com>, 
	Jiri Kosina <jikos@...nel.org>
Cc: Dylan Hatch <dylanbhatch@...gle.com>, Roman Gushchin <roman.gushchin@...ux.dev>, 
	Weinan Liu <wnliu@...gle.com>, Mark Rutland <mark.rutland@....com>, Ian Rogers <irogers@...gle.com>, 
	linux-toolchains@...r.kernel.org, linux-kernel@...r.kernel.org, 
	live-patching@...r.kernel.org, joe.lawrence@...hat.com, 
	Puranjay Mohan <puranjay@...nel.org>, Song Liu <song@...nel.org>
Subject: [PATCH v2 2/6] arm64: entry: add unwind info for various kernel entries

From: Weinan Liu <wnliu@...gle.com>

DWARF CFI (Call Frame Information) specifies how to recover the return
address and callee-saved registers at each PC in a given function.
Compilers are able to generate the CFI annotations when they compile
the code to assembly language. For handcrafted assembly, we need to
annotate them by hand.

Annotate CFI unwind info for assembly for interrupt and exception
handlers.

Signed-off-by: Weinan Liu <wnliu@...gle.com>
Signed-off-by: Dylan Hatch <dylanbhatch@...gle.com>
---
 arch/arm64/kernel/entry.S | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index f8018b5c1f9a..3148ede8c2c6 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -575,7 +575,12 @@ SYM_CODE_START_LOCAL(el\el\ht\()_\regsize\()_\label)
 	.if \el == 0
 	b	ret_to_user
 	.else
+	.cfi_startproc
+	.cfi_def_cfa_offset PT_REGS_SIZE
+	.cfi_offset 29, S_FP - PT_REGS_SIZE
+	.cfi_offset 30, S_LR - PT_REGS_SIZE
 	b	ret_to_kernel
+	.cfi_endproc
 	.endif
 SYM_CODE_END(el\el\ht\()_\regsize\()_\label)
 	.endm
@@ -889,6 +894,10 @@ SYM_FUNC_START(call_on_irq_stack)
 	add	sp, x16, #IRQ_STACK_SIZE
 	restore_irq x9
 	blr	x1
+	.cfi_startproc
+	.cfi_def_cfa 29, 16
+	.cfi_offset 29, -16
+	.cfi_offset 30, -8
 
 	save_and_disable_daif x9
 	/*
@@ -900,6 +909,7 @@ SYM_FUNC_START(call_on_irq_stack)
 	scs_load_current
 	restore_irq x9
 	ret
+	.cfi_endproc
 SYM_FUNC_END(call_on_irq_stack)
 NOKPROBE(call_on_irq_stack)
 
-- 
2.51.0.355.g5224444f11-goog