On 2025/12/8 13:48, Anshuman Khandual wrote:
> On 04/12/25 1:51 PM, Jinjie Ruan wrote:
>> 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 <[email protected]>
>> Signed-off-by: Jinjie Ruan <[email protected]>
>> ---
>> 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;
>
> regs->syscallno still remains unchanged even if syscall is evaluated to be
> different ?
No, arm64 syscall_get_nr() returns regs->syscallno, use syscall_get_nr()
helper here to get the local "syscall" is to stay consistent with the
generic entry, without any semantic change.
23 static inline int syscall_get_nr(struct task_struct *task,
24 >------->------->------->------- struct pt_regs *regs)
25 {
26 >-------return regs->syscallno;
27 }
>
>> }
>>
>> -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)
>
>
