Refactor the system call exit path to align with the generic entry framework. This consolidates thread flag checking, rseq handling, and syscall tracing into a structure that mirrors the generic syscall_exit_to_user_mode_work() implementation.
[Rationale] The generic entry code employs a hierarchical approach for syscall exit work: 1. syscall_exit_to_user_mode_work(): The entry point that handles rseq and checks if further exit work (tracing/audit) is required. 2. syscall_exit_work(): Performs the actual tracing, auditing, and ptrace reporting. [Changes] - Rename and Encapsulate: Rename syscall_trace_exit() to syscall_exit_work() and make it static, as it is now an internal helper for the exit path. - New Entry Point: Implement syscall_exit_to_user_mode_work() to replace the manual flag-reading logic in el0_svc_common(). This function now encapsulates the rseq_syscall() call and the conditional execution of syscall_exit_work(). - Simplify el0_svc_common(): Remove the complex conditional checks for tracing and CONFIG_DEBUG_RSEQ at the end of the syscall path, delegating this responsibility to the new helper. - Helper Migration: Move has_syscall_work() to asm/syscall.h to allow its reuse across ptrace.c and syscall.c. - Clean up RSEQ: Remove the explicit IS_ENABLED(CONFIG_DEBUG_RSEQ) check in the caller, as rseq_syscall() is already a no-op when the config is disabled. Cc: Will Deacon <[email protected]> Cc: Catalin Marinas <[email protected]> Reviewed-by: Kevin Brodsky <[email protected]> Signed-off-by: Jinjie Ruan <[email protected]> --- arch/arm64/include/asm/syscall.h | 7 ++++++- arch/arm64/kernel/ptrace.c | 14 +++++++++++--- arch/arm64/kernel/syscall.c | 20 +------------------- 3 files changed, 18 insertions(+), 23 deletions(-) diff --git a/arch/arm64/include/asm/syscall.h b/arch/arm64/include/asm/syscall.h index 30b203ef156b..c469d09a7964 100644 --- a/arch/arm64/include/asm/syscall.h +++ b/arch/arm64/include/asm/syscall.h @@ -120,7 +120,12 @@ static inline int syscall_get_arch(struct task_struct *task) return AUDIT_ARCH_AARCH64; } +static inline bool has_syscall_work(unsigned long flags) +{ + return unlikely(flags & _TIF_SYSCALL_WORK); +} + int syscall_trace_enter(struct pt_regs *regs, unsigned long flags); -void syscall_trace_exit(struct pt_regs *regs, unsigned long flags); +void syscall_exit_to_user_mode_work(struct pt_regs *regs); #endif /* __ASM_SYSCALL_H */ diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index f3d3dec85828..35efa2062408 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -2454,10 +2454,8 @@ int syscall_trace_enter(struct pt_regs *regs, unsigned long flags) return ret ? : syscall; } -void syscall_trace_exit(struct pt_regs *regs, unsigned long flags) +static void syscall_exit_work(struct pt_regs *regs, unsigned long flags) { - rseq_syscall(regs); - audit_syscall_exit(regs); if (flags & _TIF_SYSCALL_TRACEPOINT) @@ -2467,6 +2465,16 @@ void syscall_trace_exit(struct pt_regs *regs, unsigned long flags) report_syscall_exit(regs); } +void syscall_exit_to_user_mode_work(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); +} + /* * SPSR_ELx bits which are always architecturally RES0 per ARM DDI 0487D.a. * We permit userspace to set SSBS (AArch64 bit 12, AArch32 bit 23) which is diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index e8fd0d60ab09..66d4da641d97 100644 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -65,11 +65,6 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno, choose_random_kstack_offset(get_random_u16()); } -static inline bool has_syscall_work(unsigned long flags) -{ - return unlikely(flags & _TIF_SYSCALL_WORK); -} - static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, const syscall_fn_t syscall_table[]) { @@ -130,21 +125,8 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, } invoke_syscall(regs, scno, sc_nr, syscall_table); - - /* - * The tracing status may have changed under our feet, so we have to - * check again. However, if we were tracing entry, then we always trace - * exit regardless, as the old entry assembly did. - */ - if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) { - flags = read_thread_flags(); - if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP)) - return; - } - trace_exit: - flags = read_thread_flags(); - syscall_trace_exit(regs, flags); + syscall_exit_to_user_mode_work(regs); } void do_el0_svc(struct pt_regs *regs) -- 2.34.1
