linux-kernel - [RFC 10/16] arm64: sleep: Prevent stack frame warnings from objtool

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Message-Id: <20190516103655.5509-11-raphael.gault@arm.com>
Date:   Thu, 16 May 2019 11:36:49 +0100
From:   Raphael Gault <raphael.gault@....com>
To:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     jpoimboe@...hat.com, peterz@...radead.org, catalin.marinas@....com,
        will.deacon@....com, julien.thierry@....com,
        Raphael Gault <raphael.gault@....com>
Subject: [RFC 10/16] arm64: sleep: Prevent stack frame warnings from objtool

This code doesn't respect the Arm PCS but it is intended this
way. Adapting it to respect the PCS would result in altering the
behaviour.

In order to suppress objtool's warnings, we setup a stack frame
for __cpu_suspend_enter and annotate cpu_resume and _cpu_resume
as having non-standard stack frames.

Signed-off-by: Raphael Gault <raphael.gault@....com>
---
 arch/arm64/kernel/sleep.S | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kernel/sleep.S b/arch/arm64/kernel/sleep.S
index 3e53ffa07994..eb434525fe82 100644
--- a/arch/arm64/kernel/sleep.S
+++ b/arch/arm64/kernel/sleep.S
@@ -90,6 +90,7 @@ ENTRY(__cpu_suspend_enter)
 	str	x0, [x1]
 	add	x0, x0, #SLEEP_STACK_DATA_SYSTEM_REGS
 	stp	x29, lr, [sp, #-16]!
+	mov	x29, sp
 	bl	cpu_do_suspend
 	ldp	x29, lr, [sp], #16
 	mov	x0, #1
@@ -146,3 +147,6 @@ ENTRY(_cpu_resume)
 	mov	x0, #0
 	ret
 ENDPROC(_cpu_resume)
+
+	asm_stack_frame_non_standard cpu_resume
+	asm_stack_frame_non_standard _cpu_resume
-- 
2.17.1