On 21/11/2025 05:15, Jinjie Ruan wrote: > > On 2025/11/19 1:12, Kevin Brodsky wrote: >> On 17/11/2025 14:30, Jinjie Ruan wrote: >>> The generic entry handle error of ptrace_report_syscall_entry(), but >>> arm64 not. >> This suggests that arm64 ignores the error completely, which isn't the >> case: no syscall will be performed, but tracing will still occur as normal. >> >> What this patch seems to be doing is to abort the _enter sequence if >> ptrace_report_syscall_entry() errors out. The commit title and message >> should be reworded accordingly. > You are right,the description is unclear . > >>> As the comment said, the calling arch code should abort the system >> Which comment? > ptrace_report_syscall_entry()
I found that later, this should be clarified in the commit message. >>> call and must prevent normal entry so no system call is >>> made if ptrace_report_syscall_entry() return nonzero. >> This is already the case since we're calling forget_syscall(). > Yes. it is similar with the generic entry returns NO_SYSCALL. My point is that this patch is not changing this - arm64 was already skipping the syscall if ptrace_report_syscall_entry() returns an error. >>> 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 <[email protected]> >>> --- >>> arch/arm64/kernel/ptrace.c | 16 +++++++++++----- >>> 1 file changed, 11 insertions(+), 5 deletions(-) >>> >>> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c >>> index 95984bbf53db..707951ad5d24 100644 >>> --- a/arch/arm64/kernel/ptrace.c >>> +++ b/arch/arm64/kernel/ptrace.c >>> @@ -2317,10 +2317,10 @@ enum ptrace_syscall_dir { >>> PTRACE_SYSCALL_EXIT, >>> }; >>> >>> -static void report_syscall_enter(struct pt_regs *regs) >>> +static int report_syscall_enter(struct pt_regs *regs) >>> { >>> - int regno; >>> unsigned long saved_reg; >>> + int regno, ret; >>> >>> /* >>> * We have some ABI weirdness here in the way that we handle syscall >>> @@ -2342,9 +2342,13 @@ static void report_syscall_enter(struct pt_regs >>> *regs) >>> saved_reg = regs->regs[regno]; >>> regs->regs[regno] = PTRACE_SYSCALL_ENTER; >>> >>> - if (ptrace_report_syscall_entry(regs)) >>> + ret = ptrace_report_syscall_entry(regs); >>> + if (ret) >>> forget_syscall(regs); >> The generic syscall_trace_enter() doesn't do this (i.e. setting >> regs->syscallno to NO_SYSCALL). Is that an oversight or do we just not >> need it? In principle this does have a visible effect (e.g. via >> REGSET_SYSTEM_CALL). > We just not need it because the original syscall_trace_enter() need use > regs->syscallno as the return value, but now we return early by using > NO_SYSCALL. Calling forget_syscall() means setting regs->syscallno to NO_SYSCALL. It is indeed no longer required for the entry sequence, but it does have visible side effects. For instance, regs->syscallno can be inspected via ptrace(PTRACE_GETREGSET, REGSET_SYSTEM_CALL). So the question is whether we need to deviate from the generic path on arm64 (this is mostly a question for arm64 maintainers). - Kevin
