linux-kernel - [PATCH v2 1/1] arm64: Do not forget syscall when starting a new thread.

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Message-Id: <20220608162447.666494-2-flaniel@linux.microsoft.com>
Date:   Wed,  8 Jun 2022 17:24:46 +0100
From:   Francis Laniel <flaniel@...ux.microsoft.com>
To:     linux-trace-devel@...r.kernel.org
Cc:     James Morse <james.morse@....com>,
        Daniel Kiss <daniel.kiss@....com>,
        Francis Laniel <flaniel@...ux.microsoft.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Mark Brown <broonie@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/1] arm64: Do not forget syscall when starting a new thread.

This patch enables exeve*() to be traced with syscalls:sys_exit_execve
tracepoint.
Previous to it, by calling forget_syscall(), this tracepoint would not
print its information as syscall is -1.
So, this patch removes call to forget_syscall() and set regs->syscallno
to its previous value.

Signed-off-by: Francis Laniel <flaniel@...ux.microsoft.com>
---
 arch/arm64/include/asm/processor.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
index 9e58749db21d..86eb0bfe3b38 100644
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -272,8 +272,9 @@ void tls_preserve_current_state(void);
 
 static inline void start_thread_common(struct pt_regs *regs, unsigned long pc)
 {
+	s32 previous_syscall = regs->syscallno;
 	memset(regs, 0, sizeof(*regs));
-	forget_syscall(regs);
+	regs->syscallno = previous_syscall;
 	regs->pc = pc;
 
 	if (system_uses_irq_prio_masking())
-- 
2.25.1