linux-kernel - [PATCH v9 04/16] arm64/ptrace: Refactor syscall_trace

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Message-ID: <20251204082123.2792067-5-ruanjinjie@huawei.com>
Date: Thu, 4 Dec 2025 16:21:11 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: <catalin.marinas@....com>, <will@...nel.org>, <oleg@...hat.com>,
	<tglx@...utronix.de>, <peterz@...radead.org>, <luto@...nel.org>,
	<shuah@...nel.org>, <kees@...nel.org>, <wad@...omium.org>, <deller@....de>,
	<macro@...am.me.uk>, <charlie@...osinc.com>, <kevin.brodsky@....com>,
	<ldv@...ace.io>, <mark.rutland@....com>, <song@...nel.org>,
	<ryan.roberts@....com>, <ada.coupriediaz@....com>,
	<anshuman.khandual@....com>, <broonie@...nel.org>, <pengcan@...inos.cn>,
	<dvyukov@...gle.com>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>
CC: <ruanjinjie@...wei.com>
Subject: [PATCH v9 04/16] arm64/ptrace: Refactor syscall_trace_enter/exit()

The generic syscall entry code has the following form, which use
the input syscall work flag and syscall number:

| syscall_trace_enter(struct pt_regs *regs, long syscall,
|		      unsigned long work)
|
| syscall_exit_work(struct pt_regs *regs, unsigned long work)

In preparation for moving arm64 over to the generic entry code,
refactor syscall_trace_enter/exit() to also pass thread flags, and
get syscall number by syscall_get_nr() helper.

No functional changes.

Reviewed-by: Kevin Brodsky <kevin.brodsky@....com>
Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
---
 arch/arm64/include/asm/syscall.h |  4 ++--
 arch/arm64/kernel/ptrace.c       | 25 ++++++++++++++++---------
 arch/arm64/kernel/syscall.c      |  5 +++--
 3 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h
index 5e4c7fc44f73..cef1d9ce6e1b 100644
--- a/arch/arm64/include/asm/syscall.h
+++ b/arch/arm64/include/asm/syscall.h
@@ -120,7 +120,7 @@ static inline int syscall_get_arch(struct task_struct *task)
 	return AUDIT_ARCH_AARCH64;
 }
 
-int syscall_trace_enter(struct pt_regs *regs);
-void syscall_trace_exit(struct pt_regs *regs);
+int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags);
+void syscall_trace_exit(struct pt_regs *regs, unsigned long flags);
 
 #endif	/* __ASM_SYSCALL_H */
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 3926ce6aa268..b962cbcca11d 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -2381,9 +2381,8 @@ static void report_syscall_exit(struct pt_regs *regs)
 	}
 }
 
-int syscall_trace_enter(struct pt_regs *regs)
+int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags)
 {
-	unsigned long flags = read_thread_flags();
 	int ret;
 
 	if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
@@ -2396,19 +2395,27 @@ int syscall_trace_enter(struct pt_regs *regs)
 	if (secure_computing() == -1)
 		return NO_SYSCALL;
 
-	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
-		trace_sys_enter(regs, regs->syscallno);
+	/* Either of the above might have changed the syscall number */
+	syscall = syscall_get_nr(current, regs);
 
-	audit_syscall_entry(regs->syscallno, regs->orig_x0, regs->regs[1],
+	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT)) {
+		trace_sys_enter(regs, syscall);
+
+		/*
+		 * Probes or BPF hooks in the tracepoint may have changed the
+		 * system call number as well.
+		 */
+		 syscall = syscall_get_nr(current, regs);
+	}
+
+	audit_syscall_entry(syscall, regs->orig_x0, regs->regs[1],
 			    regs->regs[2], regs->regs[3]);
 
-	return regs->syscallno;
+	return syscall;
 }
 
-void syscall_trace_exit(struct pt_regs *regs)
+void syscall_trace_exit(struct pt_regs *regs, unsigned long flags)
 {
-	unsigned long flags = read_thread_flags();
-
 	audit_syscall_exit(regs);
 
 	if (flags & _TIF_SYSCALL_TRACEPOINT)
diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c
index aba7ca6bca2d..ec31f82d2e9f 100644
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -124,7 +124,7 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 		 */
 		if (scno == NO_SYSCALL)
 			syscall_set_return_value(current, regs, -ENOSYS, 0);
-		scno = syscall_trace_enter(regs);
+		scno = syscall_trace_enter(regs, scno, flags);
 		if (scno == NO_SYSCALL)
 			goto trace_exit;
 	}
@@ -143,7 +143,8 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
 	}
 
 trace_exit:
-	syscall_trace_exit(regs);
+	flags = read_thread_flags();
+	syscall_trace_exit(regs, flags);
 }
 
 void do_el0_svc(struct pt_regs *regs)
-- 
2.34.1