linux-kernel - [PATCH 2/8] arm64: entry: add unwind info for various kernel entries

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Message-ID: <20250127213310.2496133-3-wnliu@google.com>
Date: Mon, 27 Jan 2025 21:33:04 +0000
From: Weinan Liu <wnliu@...gle.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>, Steven Rostedt <rostedt@...dmis.org>, 
	Indu Bhagat <indu.bhagat@...cle.com>, Peter Zijlstra <peterz@...radead.org>
Cc: Mark Rutland <mark.rutland@....com>, roman.gushchin@...ux.dev, 
	Will Deacon <will@...nel.org>, Ian Rogers <irogers@...gle.com>, linux-toolchains@...r.kernel.org, 
	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org, 
	joe.lawrence@...hat.com, linux-arm-kernel@...ts.infradead.org, 
	Weinan Liu <wnliu@...gle.com>
Subject: [PATCH 2/8] arm64: entry: add unwind info for various kernel entries

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>
---
 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 5ae2a34b50bd..fe3e3e29ee5d 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -579,7 +579,12 @@ 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)
 	/* Move to the new stack and call the function there */
 	add	sp, x16, #IRQ_STACK_SIZE
 	blr	x1
+	.cfi_startproc
+	.cfi_def_cfa 29, 16
+	.cfi_offset 29, -16
+	.cfi_offset 30, -8
 
 	/*
 	 * Restore the SP from the FP, and restore the FP and LR from the frame
@@ -898,6 +907,7 @@ SYM_FUNC_START(call_on_irq_stack)
 	ldp	x29, x30, [sp], #16
 	scs_load_current
 	ret
+	.cfi_endproc
 SYM_FUNC_END(call_on_irq_stack)
 NOKPROBE(call_on_irq_stack)
 
-- 
2.48.1.262.g85cc9f2d1e-goog