linux-kernel - [PATCH 08/11] powerpc/40x: add exception frame marker

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Message-Id: <96a6861f3b7ec6ca2a59ee50c327fa5f2d03bbee.1548673552.git.christophe.leroy@c-s.fr>
Date:   Mon, 28 Jan 2019 11:11:27 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 08/11] powerpc/40x: add exception frame marker

This patch adds STACK_FRAME_REGS_MARKER in the stack at exception entry
in order to see interrupts in call traces as below:

[    0.013964] Call Trace:
[    0.014014] [c0745db0] [c007a9d4] tick_periodic.constprop.5+0xd8/0x104 (unreliable)
[    0.014086] [c0745dc0] [c007aa20] tick_handle_periodic+0x20/0x9c
[    0.014181] [c0745de0] [c0009cd0] timer_interrupt+0xa0/0x264
[    0.014258] [c0745e10] [c000e484] ret_from_except+0x0/0x14
[    0.014390] --- interrupt: 901 at console_unlock.part.7+0x3f4/0x528
[    0.014390]     LR = console_unlock.part.7+0x3f0/0x528
[    0.014455] [c0745ee0] [c0050334] console_unlock.part.7+0x114/0x528 (unreliable)
[    0.014542] [c0745f30] [c00524e0] register_console+0x3d8/0x44c
[    0.014625] [c0745f60] [c0675aac] cpm_uart_console_init+0x18/0x2c
[    0.014709] [c0745f70] [c06614f4] console_init+0x114/0x1cc
[    0.014795] [c0745fb0] [c0658b68] start_kernel+0x300/0x3d8
[    0.014864] [c0745ff0] [c00022cc] start_here+0x44/0x98

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/kernel/head_40x.S | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 59f6f53f1ac2..f3bfb695f952 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -132,6 +132,9 @@ _ENTRY(saved_ksp_limit)
 	tovirt(r1,r11);			/* set new kernel sp */	\
 	rlwinm	r9,r9,0,14,12;		/* clear MSR_WE (necessary?)	   */\
 	stw	r0,GPR0(r11);						     \
+	lis	r10, STACK_FRAME_REGS_MARKER@ha; /* exception frame marker */\
+	addi	r10, r10, STACK_FRAME_REGS_MARKER@l;			     \
+	stw	r10, 8(r11);						     \
 	SAVE_4GPRS(3, r11);						     \
 	SAVE_2GPRS(7, r11)
 
@@ -174,6 +177,9 @@ _ENTRY(saved_ksp_limit)
 	tovirt(r1,r11);							     \
 	rlwinm	r9,r9,0,14,12;		/* clear MSR_WE (necessary?)	   */\
 	stw	r0,GPR0(r11);						     \
+	lis	r10, STACK_FRAME_REGS_MARKER@ha; /* exception frame marker */\
+	addi	r10, r10, STACK_FRAME_REGS_MARKER@l;			     \
+	stw	r10, 8(r11);						     \
 	SAVE_4GPRS(3, r11);						     \
 	SAVE_2GPRS(7, r11)
 
-- 
2.13.3