linux-kernel - [PATCH -next 4/7] riscv: syscall: Don't clobber s0 when syscall

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Date:   Tue, 20 Sep 2022 23:11:59 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <linux-riscv@...ts.infradead.org>,
        <linux-perf-users@...r.kernel.org>
CC:     <paul.walmsley@...ive.com>, <palmer@...belt.com>,
        <aou@...s.berkeley.edu>, <peterz@...radead.org>,
        <mingo@...hat.com>, <acme@...nel.org>, <mark.rutland@....com>,
        <alexander.shishkin@...ux.intel.com>, <namhyung@...nel.org>,
        <jolsa@...nel.org>, <guoren@...nel.org>, <nsaenzju@...hat.com>,
        <frederic@...nel.org>, <changbin.du@...el.com>,
        <vincent.chen@...ive.com>, <ardb@...nel.org>,
        <mhiramat@...nel.org>, <rostedt@...dmis.org>,
        <keescook@...omium.org>, <catalin.marinas@....com>,
        <chenzhongjin@...wei.com>
Subject: [PATCH -next 4/7] riscv: syscall: Don't clobber s0 when syscall

syscall uses s0 to load address of sys_call_table.

Since now we uses s0 to save pt_regs for unwinding, clobber
s0 can make unwinder treat s0 as pt_regs address. Use s1 for
this job.

Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
---
 arch/riscv/kernel/entry.S | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index ecb15c7430b4..a3b14a649782 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -205,33 +205,33 @@ handle_syscall:
 check_syscall_nr:
 	/* Check to make sure we don't jump to a bogus syscall number. */
 	li t0, __NR_syscalls
-	la s0, sys_ni_syscall
+	la s1, sys_ni_syscall
 	/*
 	 * Syscall number held in a7.
 	 * If syscall number is above allowed value, redirect to ni_syscall.
 	 */
 	bgeu a7, t0, 3f
 #ifdef CONFIG_COMPAT
-	REG_L s0, PT_STATUS(sp)
-	srli s0, s0, SR_UXL_SHIFT
-	andi s0, s0, (SR_UXL >> SR_UXL_SHIFT)
+	REG_L s1, PT_STATUS(sp)
+	srli s1, s1, SR_UXL_SHIFT
+	andi s1, s1, (SR_UXL >> SR_UXL_SHIFT)
 	li t0, (SR_UXL_32 >> SR_UXL_SHIFT)
-	sub t0, s0, t0
+	sub t0, s1, t0
 	bnez t0, 1f
 
 	/* Call compat_syscall */
-	la s0, compat_sys_call_table
+	la s1, compat_sys_call_table
 	j 2f
 1:
 #endif
 	/* Call syscall */
-	la s0, sys_call_table
+	la s1, sys_call_table
 2:
 	slli t0, a7, RISCV_LGPTR
-	add s0, s0, t0
-	REG_L s0, 0(s0)
+	add s1, s1, t0
+	REG_L s1, 0(s1)
 3:
-	jalr s0
+	jalr s1
 
 ret_from_syscall:
 	/* Set user a0 to kernel a0 */
-- 
2.17.1