On 26/11/2025 08:14, Jinjie Ruan wrote:
> Currently, x86, Riscv, Loongarch use the generic entry which makes
> maintainers' work easier and codes more elegant. arm64 has already
> switched to the generic IRQ entry, so completely convert arm64 to use
> the generic entry infrastructure from kernel/entry/*.
>
> The changes are below:
> - Remove TIF_SYSCALL_* flag, _TIF_WORK_MASK, _TIF_SYSCALL_WORK,
_TIF_WORK_MASK is now removed in patch 1.
> and remove has_syscall_work(), as _TIF_SYSCALL_WORK is equal with
> SYSCALL_WORK_ENTER.
>
> [...]
>
> +static __always_inline void arch_ptrace_report_syscall_exit(struct pt_regs
> *regs,
> + int step)
> +{
> + unsigned long saved_reg;
> + int regno;
> +
> + saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_EXIT, ®no);
> + if (!step) {
A difference I noticed here is that the generic report_single_step()
always returns false if SYSCALL_EMU is set. I don't know if the
combination of SYSCALL_EMU and SINGLESTEP is meaningful, but if it is
then I think that's a behaviour change.
> + ptrace_report_syscall_exit(regs, 0);
> + regs->regs[regno] = saved_reg;
> + } else {
> + regs->regs[regno] = saved_reg;
> +
> + /*
> + * Signal a pseudo-step exception since we are stepping but
> + * tracer modifications to the registers may have rewound the
> + * state machine.
> + */
> + ptrace_report_syscall_exit(regs, 1);
> + }
> +}
> +
> +#define arch_ptrace_report_syscall_exit arch_ptrace_report_syscall_exit
> +
> #endif /* _ASM_ARM64_ENTRY_COMMON_H */
> diff --git a/arch/arm64/include/asm/syscall.h
> b/arch/arm64/include/asm/syscall.h
> index 6225981fbbdb..f705ba2bb6fd 100644
> --- a/arch/arm64/include/asm/syscall.h
> +++ b/arch/arm64/include/asm/syscall.h
> @@ -9,6 +9,9 @@
> #include <linux/compat.h>
> #include <linux/err.h>
>
> +#include <asm/compat.h>
> +#include <asm/vdso.h>
> +
> typedef long (*syscall_fn_t)(const struct pt_regs *regs);
>
> extern const syscall_fn_t sys_call_table[];
> @@ -114,12 +117,21 @@ static inline int syscall_get_arch(struct task_struct
> *task)
> return AUDIT_ARCH_AARCH64;
> }
>
> -static inline bool has_syscall_work(unsigned long flags)
> +static inline bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
> {
> - return unlikely(flags & _TIF_SYSCALL_WORK);
> + unsigned long sigtramp;
> +
> +#ifdef CONFIG_COMPAT
> + if (is_compat_task()) {
> + unsigned long vdso = (unsigned
> long)current->mm->context.sigpage;
Might as well call it sigpage (separate from the vDSO on arm32).
> +
> + return (regs->pc >= vdso && regs->pc < (vdso + PAGE_SIZE));
Nit: no need for parentheses around the expression to return.
> + }
> +#endif
> + sigtramp = (unsigned long)VDSO_SYMBOL(current->mm->context.vdso,
> sigtramp);
> + return regs->pc == (sigtramp + 8);
> }
>
> -int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long
> flags);
> -void syscall_exit_to_user_mode_prepare(struct pt_regs *regs);
> +#define ARCH_SYSCALL_WORK_EXIT (_TIF_SECCOMP | _TIF_SYSCALL_EMU)
>
> #endif /* __ASM_SYSCALL_H */
> diff --git a/arch/arm64/include/asm/thread_info.h
> b/arch/arm64/include/asm/thread_info.h
> index ff4998fa1844..d3142b5d1b9c 100644
> --- a/arch/arm64/include/asm/thread_info.h
> +++ b/arch/arm64/include/asm/thread_info.h
> @@ -43,6 +43,7 @@ struct thread_info {
> void *scs_sp;
> #endif
> u32 cpu;
> + unsigned long syscall_work; /* SYSCALL_WORK_ flags */
> };
>
> #define thread_saved_pc(tsk) \
> @@ -65,11 +66,8 @@ void arch_setup_new_exec(void);
> #define TIF_UPROBE 5 /* uprobe breakpoint or singlestep */
> #define TIF_MTE_ASYNC_FAULT 6 /* MTE Asynchronous Tag Check Fault */
> #define TIF_NOTIFY_SIGNAL 7 /* signal notifications exist */
> -#define TIF_SYSCALL_TRACE 8 /* syscall trace active */
> -#define TIF_SYSCALL_AUDIT 9 /* syscall auditing */
> -#define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for
> ftrace */
> -#define TIF_SECCOMP 11 /* syscall secure computing */
> -#define TIF_SYSCALL_EMU 12 /* syscall emulation active */
> +#define TIF_SECCOMP 11 /* syscall secure computing */
> +#define TIF_SYSCALL_EMU 12 /* syscall emulation active */
These seem to have reappeared in v8 for some reason?
> #define TIF_PATCH_PENDING 13 /* pending live patching update */
> #define TIF_MEMDIE 18 /* is terminating due to OOM killer */
> #define TIF_FREEZE 19
> @@ -92,24 +90,16 @@ void arch_setup_new_exec(void);
> #define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY)
> #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
> #define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE)
> -#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
> -#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
> -#define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
> #define _TIF_SECCOMP (1 << TIF_SECCOMP)
> #define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU)
Ditto.
> #define _TIF_PATCH_PENDING (1 << TIF_PATCH_PENDING)
> #define _TIF_UPROBE (1 << TIF_UPROBE)
> -#define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP)
> #define _TIF_32BIT (1 << TIF_32BIT)
> #define _TIF_SVE (1 << TIF_SVE)
> #define _TIF_MTE_ASYNC_FAULT (1 << TIF_MTE_ASYNC_FAULT)
> #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL)
> #define _TIF_TSC_SIGSEGV (1 << TIF_TSC_SIGSEGV)
>
> -#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
> - _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
> - _TIF_SYSCALL_EMU)
> -
> #ifdef CONFIG_SHADOW_CALL_STACK
> #define INIT_SCS \
> .scs_base = init_shadow_call_stack, \
> diff --git a/arch/arm64/kernel/debug-monitors.c
> b/arch/arm64/kernel/debug-monitors.c
> index 29307642f4c9..e67643a70405 100644
> --- a/arch/arm64/kernel/debug-monitors.c
> +++ b/arch/arm64/kernel/debug-monitors.c
> @@ -385,11 +385,18 @@ void user_enable_single_step(struct task_struct *task)
>
> if (!test_and_set_ti_thread_flag(ti, TIF_SINGLESTEP))
> set_regs_spsr_ss(task_pt_regs(task));
> +
> + /*
> + * Ensure that a trap is triggered once stepping out of a system
> + * call prior to executing any user instruction.
> + */
> + set_task_syscall_work(task, SYSCALL_EXIT_TRAP);
> }
> NOKPROBE_SYMBOL(user_enable_single_step);
>
> void user_disable_single_step(struct task_struct *task)
> {
> clear_ti_thread_flag(task_thread_info(task), TIF_SINGLESTEP);
> + clear_task_syscall_work(task, SYSCALL_EXIT_TRAP);
> }
> NOKPROBE_SYMBOL(user_disable_single_step);
> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
> index c2bd0130212d..9e3b39e207d1 100644
> --- a/arch/arm64/kernel/ptrace.c
> +++ b/arch/arm64/kernel/ptrace.c
> @@ -42,9 +42,6 @@
> #include <asm/traps.h>
> #include <asm/system_misc.h>
>
> -#define CREATE_TRACE_POINTS
> -#include <trace/events/syscalls.h>
> -
> struct pt_regs_offset {
> const char *name;
> int offset;
> @@ -2312,141 +2309,6 @@ long arch_ptrace(struct task_struct *child, long
> request,
> return ptrace_request(child, request, addr, data);
> }
>
> -enum ptrace_syscall_dir {
> - PTRACE_SYSCALL_ENTER = 0,
> - PTRACE_SYSCALL_EXIT,
> -};
> -
> -static inline unsigned long ptrace_save_reg(struct pt_regs *regs,
> - enum ptrace_syscall_dir dir,
> - int *regno)
> -{
> - unsigned long saved_reg;
> -
> - /*
> - * We have some ABI weirdness here in the way that we handle syscall
> - * exit stops because we indicate whether or not the stop has been
> - * signalled from syscall entry or syscall exit by clobbering a general
> - * purpose register (ip/r12 for AArch32, x7 for AArch64) in the tracee
> - * and restoring its old value after the stop. This means that:
> - *
> - * - Any writes by the tracer to this register during the stop are
> - * ignored/discarded.
> - *
> - * - The actual value of the register is not available during the stop,
> - * so the tracer cannot save it and restore it later.
> - *
> - * - Syscall stops behave differently to seccomp and pseudo-step traps
> - * (the latter do not nobble any registers).
> - */
> - *regno = (is_compat_task() ? 12 : 7);
> - saved_reg = regs->regs[*regno];
> - regs->regs[*regno] = dir;
> -
> - return saved_reg;
> -}
> -
> -static int report_syscall_entry(struct pt_regs *regs)
> -{
> - unsigned long saved_reg;
> - int regno, ret;
> -
> - saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_ENTER, ®no);
> - 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)
> -{
> - unsigned long saved_reg;
> - int regno;
> -
> - saved_reg = ptrace_save_reg(regs, PTRACE_SYSCALL_EXIT, ®no);
> - if (!test_thread_flag(TIF_SINGLESTEP)) {
> - ptrace_report_syscall_exit(regs, 0);
> - regs->regs[regno] = saved_reg;
> - } else {
> - regs->regs[regno] = saved_reg;
> -
> - /*
> - * Signal a pseudo-step exception since we are stepping but
> - * tracer modifications to the registers may have rewound the
> - * state machine.
> - */
> - ptrace_report_syscall_exit(regs, 1);
> - }
> -}
> -
> -static inline void syscall_enter_audit(struct pt_regs *regs, long syscall)
> -{
> - if (unlikely(audit_context())) {
> - unsigned long args[6];
> -
> - syscall_get_arguments(current, regs, args);
> - audit_syscall_entry(syscall, args[0], args[1], args[2],
> args[3]);
> - }
> -}
> -
> -int syscall_trace_enter(struct pt_regs *regs, long syscall, unsigned long
> flags)
> -{
> - int ret;
> -
> - if (flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) {
> - ret = report_syscall_entry(regs);
> - if (ret || (flags & _TIF_SYSCALL_EMU))
> - return NO_SYSCALL;
> - }
> -
> - /* Do the secure computing after ptrace; failures should be fast. */
> - if (flags & _TIF_SECCOMP) {
> - ret = __secure_computing();
> - if (ret == -1)
> - return NO_SYSCALL;
> - }
> -
> - /* Either of the above might have changed the syscall number */
> - syscall = syscall_get_nr(current, regs);
> -
> - 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);
> - }
> -
> - syscall_enter_audit(regs, syscall);
> -
> - return ret ? : syscall;
> -}
> -
> -static void syscall_exit_work(struct pt_regs *regs, unsigned long flags)
> -{
> - audit_syscall_exit(regs);
> -
> - if (flags & _TIF_SYSCALL_TRACEPOINT)
> - trace_sys_exit(regs, syscall_get_return_value(current, regs));
> -
> - if (flags & (_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP))
> - report_syscall_exit(regs);
> -}
> -
> -void syscall_exit_to_user_mode_prepare(struct pt_regs *regs)
> -{
> - unsigned long flags = read_thread_flags();
> -
> - rseq_syscall(regs);
> -
> - if (has_syscall_work(flags) || flags & _TIF_SINGLESTEP)
> - syscall_exit_work(regs, flags);
> -}
Aside from the small change in arch_ptrace_report_syscall_exit(), these
look exactly equivalent to the generic functions, so LGTM.
- Kevin
