Re: [PATCH v8 06/12] arm64/ptrace: Return early for ptrace_report_syscall_entry() error

On 26/11/2025 08:14, Jinjie Ruan wrote:

The generic entry abort the syscall_trace_enter() sequence if ptrace_report_syscall_entry() errors out, but arm64 not.

As the ptrace_report_syscall_entry() comment said, the calling arch code should abort the system call and must prevent normal entry so no system call is made if ptrace_report_syscall_entry() return nonzero.

Which is already the case on arm64 before patch 2, which changes syscall_trace_enter() so that it no longer returns regs->syscallno, meaning that forget_syscall() no longer skips the syscall.

The most sensible thing to do is probably to move this patch before patch 2. This ensures patch 2 doesn't introduce a regression, and then the only effect of this patch is to abort the trace sequence early.

- Kevin

In preparation for moving arm64 over to the generic entry code, return early if ptrace_report_syscall_entry() encounters an error.

Signed-off-by: Jinjie Ruan ruanjinjie@huawei.com

arch/arm64/kernel/ptrace.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 233a7688ac94..da9687d30bcf 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -2346,15 +2346,18 @@ static inline unsigned long ptrace_save_reg(struct pt_regs *regs, return saved_reg; } -static void report_syscall_entry(struct pt_regs *regs) +static int report_syscall_entry(struct pt_regs *regs) { unsigned long saved_reg;

• int regno;

• int regno, ret;

saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_ENTER, &regno);

• if (ptrace_report_syscall_entry(regs))

• ret = ptrace_report_syscall_entry(regs);
• if (ret) forget_syscall(regs); regs->regs[regno] = saved_reg;
• return ret;

} static void report_syscall_exit(struct pt_regs *regs) @@ -2380,9 +2383,11 @@ static void report_syscall_exit(struct pt_regs *regs) int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long flags) {

• int ret;
• if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {

• report_syscall_entry(regs);
  

• if (flags & _TIF_SYSCALL_EMU)
  

• ret = report_syscall_entry(regs);
  

• if (ret || (flags & _TIF_SYSCALL_EMU))
  return NO_SYSCALL;
  

  }