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Message-ID: <20230724121655.7894-1-lecopzer.chen@mediatek.com>
Date: Mon, 24 Jul 2023 20:16:55 +0800
From: Lecopzer Chen <lecopzer.chen@...iatek.com>
To: <arnd@...db.de>, <linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>
CC: <linux@...linux.org.uk>, <linus.walleij@...aro.org>,
<yj.chiang@...iatek.com>,
Lecopzer Chen <lecopzer.chen@...iatek.com>
Subject: [PATCH] ARM: ptrace: fix scno of -1 cause SIGILL
In commit [1], the -1 scno is used as a special scno when the task's
syscall is traced.
After commit [2], PTRACE_SET_SYSCALL will always mask syscall with
__NR_SYSCALL_MASK, this makes the condition `cmp scno, #-1` broken,
and some test like Android VTS[3] is also failed because SIGILL
interrupt the test program.
Let's test with `and` logic with #0x0ff000. Instead of #__NR_SYSCALL_MASK
because of the constraint of ARM Operand2 rules and avoid conflicting
with ARM private syscall.
[1] commit ad75b51459ae ("ARM: 7579/1: arch/allow a scno of -1 to not cause a SIGILL")
[2] commit 4e57a4ddf6b0 ("ARM: 9107/1: syscall: always store thread_info->abi_syscall")
[3] vts_linux_kselftest_arm_32 seccomp_seccomp_bpf_arm_32#seccomp_seccomp_bpf_arm_32
Fixes: 4e57a4ddf6b0 ("ARM: 9107/1: syscall: always store thread_info->abi_syscall")
Signed-off-by: Lecopzer Chen <lecopzer.chen@...iatek.com>
---
arch/arm/kernel/entry-common.S | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index bcc4c9ec3aa4..8ff3ff476266 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -298,8 +298,15 @@ __sys_trace:
bl syscall_trace_enter
mov scno, r0
invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1
- cmp scno, #-1 @ skip the syscall?
- bne 2b
+ /*
+ * We'd like to skip scno=-1 for avoiding SIGILL for tracer,
+ * however, tracer or seccomp may have changed syscall and masked
+ * with __NR_SYSCALL_MASK, make sure -1 is compared with correct
+ * masked syscall number.
+ */
+ and r10, scno, #0x0ff000
+ cmp r10, #0x0ff000
+ bne 2b
add sp, sp, #S_OFF @ restore stack
__sys_trace_return_nosave:
--
2.18.0
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