linux-kernel - [RFC PATCH v4 35/37] arm64: entry: Annotate code switching to tasks

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Date:   Fri, 29 Apr 2022 17:43:53 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-arch@...r.kernel.org>
CC:     <jthierry@...hat.com>, <catalin.marinas@....com>,
        <will@...nel.org>, <masahiroy@...nel.org>, <jpoimboe@...hat.com>,
        <peterz@...radead.org>, <ycote@...hat.com>,
        <herbert@...dor.apana.org.au>, <mark.rutland@....com>,
        <davem@...emloft.net>, <ardb@...nel.org>, <maz@...nel.org>,
        <tglx@...utronix.de>, <luc.vanoostenryck@...il.com>,
        <chenzhongjin@...wei.com>
Subject: [RFC PATCH v4 35/37] arm64: entry: Annotate code switching to tasks

From: Julien Thierry <jthierry@...hat.com>

Add UNWIND_HINT_REGS in kernel_entry after saving pt_regs.

Whether returning to userland or creating a new task, sp is
pointing to a pt_regs frame.

Signed-off-by: Julien Thierry <jthierry@...hat.com>
Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
---
 arch/arm64/kernel/entry.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index eeb576ec97ba..c7ab5143949f 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -220,6 +220,7 @@ alternative_cb_end
 	stp	x24, x25, [sp, #16 * 12]
 	stp	x26, x27, [sp, #16 * 13]
 	stp	x28, x29, [sp, #16 * 14]
+	UNWIND_HINT_REGS
 
 	.if	\el == 0
 	clear_gp_regs
@@ -602,6 +603,7 @@ SYM_CODE_START_LOCAL(ret_to_kernel)
 SYM_CODE_END(ret_to_kernel)
 
 SYM_CODE_START_LOCAL(ret_to_user)
+	UNWIND_HINT_REGS
 	ldr	x19, [tsk, #TSK_TI_FLAGS]	// re-check for single-step
 	enable_step_tsk x19, x2
 #ifdef CONFIG_GCC_PLUGIN_STACKLEAK
@@ -874,6 +876,7 @@ NOKPROBE(cpu_switch_to)
  * This is how we return from a fork.
  */
 SYM_CODE_START(ret_from_fork)
+	UNWIND_HINT_REGS
 	bl	schedule_tail
 	cbz	x19, 1f				// not a kernel thread
 	mov	x0, x20
-- 
2.17.1