From: Roland McGrath This patch just directly clones Davide Libenzi's i386 code for x86-64 in both 64-bit and 32-bit cases. With this, the behavior of single-stepping all system calls is consistent. The syscall exit tracing caused by TIF_SINGLESTEP is superfluous in the case of sysret returns, but harmlessly so (since continuing afterward with PTRACE_CONT will have cleared TF as well as TIF_SINGLESTEP). I figured that little bit of extra processing in the single-step case was better than adding code to ignore the flag in the sysret case. Signed-off-by: Roland McGrath Signed-off-by: Andrew Morton --- 25-akpm/arch/x86_64/kernel/entry.S | 2 +- 25-akpm/arch/x86_64/kernel/ptrace.c | 7 ++++++- 2 files changed, 7 insertions(+), 2 deletions(-) diff -puN arch/x86_64/kernel/entry.S~x86-64-singlestep-through-sigreturn-system-call-2 arch/x86_64/kernel/entry.S --- 25/arch/x86_64/kernel/entry.S~x86-64-singlestep-through-sigreturn-system-call-2 2004-07-26 15:35:13.814228760 -0700 +++ 25-akpm/arch/x86_64/kernel/entry.S 2004-07-26 15:35:13.819228000 -0700 @@ -297,7 +297,7 @@ int_very_careful: sti SAVE_REST /* Check for syscall exit trace */ - testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT),%edx + testl $(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT|_TIF_SINGLESTEP),%edx jz int_signal pushq %rdi leaq 8(%rsp),%rdi # &ptregs -> arg1 diff -puN arch/x86_64/kernel/ptrace.c~x86-64-singlestep-through-sigreturn-system-call-2 arch/x86_64/kernel/ptrace.c --- 25/arch/x86_64/kernel/ptrace.c~x86-64-singlestep-through-sigreturn-system-call-2 2004-07-26 15:35:13.815228608 -0700 +++ 25-akpm/arch/x86_64/kernel/ptrace.c 2004-07-26 15:35:13.820227848 -0700 @@ -88,6 +88,7 @@ void ptrace_disable(struct task_struct * { long tmp; + clear_tsk_thread_flag(child, TIF_SINGLESTEP); tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG; put_stack_long(child, EFL_OFFSET, tmp); } @@ -344,6 +345,7 @@ asmlinkage long sys_ptrace(long request, set_tsk_thread_flag(child,TIF_SYSCALL_TRACE); else clear_tsk_thread_flag(child,TIF_SYSCALL_TRACE); + clear_tsk_thread_flag(child, TIF_SINGLESTEP); child->exit_code = data; /* make sure the single step bit is not set. */ tmp = get_stack_long(child, EFL_OFFSET); @@ -395,6 +397,7 @@ asmlinkage long sys_ptrace(long request, ret = 0; if (child->state == TASK_ZOMBIE) /* already dead */ break; + clear_tsk_thread_flag(child, TIF_SINGLESTEP); child->exit_code = SIGKILL; /* make sure the single step bit is not set. */ tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG; @@ -416,6 +419,7 @@ asmlinkage long sys_ptrace(long request, } tmp = get_stack_long(child, EFL_OFFSET) | TRAP_FLAG; put_stack_long(child, EFL_OFFSET, tmp); + set_tsk_thread_flag(child, TIF_SINGLESTEP); child->exit_code = data; /* give it a chance to run. */ wake_up_process(child); @@ -528,7 +532,8 @@ asmlinkage void syscall_trace_leave(stru if (unlikely(current->audit_context)) audit_syscall_exit(current, regs->rax); - if (test_thread_flag(TIF_SYSCALL_TRACE) + if ((test_thread_flag(TIF_SYSCALL_TRACE) + || test_thread_flag(TIF_SINGLESTEP)) && (current->ptrace & PT_PTRACED)) syscall_trace(regs); } _