From: Bodo Stroesser This patch implements the new ptrace option PTRACE_SYSEMU_SINGLESTEP, which can be used by UML to singlestep a process: it will receive SINGLESTEP interceptions for normal instructions and syscalls, but syscall execution will be skipped just like with PTRACE_SYSEMU. Signed-off-by: Bodo Stroesser Signed-off-by: Paolo 'Blaisorblade' Giarrusso Cc: Jeff Dike Signed-off-by: Andrew Morton --- arch/i386/kernel/ptrace.c | 21 +++++++++++++++++---- include/linux/ptrace.h | 1 + 2 files changed, 18 insertions(+), 4 deletions(-) diff -puN arch/i386/kernel/ptrace.c~uml-support-add-ptrace_sysemu_singlestep-option-to-i386 arch/i386/kernel/ptrace.c --- devel/arch/i386/kernel/ptrace.c~uml-support-add-ptrace_sysemu_singlestep-option-to-i386 2005-07-27 12:16:16.000000000 -0700 +++ devel-akpm/arch/i386/kernel/ptrace.c 2005-07-27 12:16:16.000000000 -0700 @@ -547,11 +547,17 @@ asmlinkage int sys_ptrace(long request, wake_up_process(child); break; + case PTRACE_SYSEMU_SINGLESTEP: /* Same as SYSEMU, but singlestep if not syscall */ case PTRACE_SINGLESTEP: /* set the trap flag. */ ret = -EIO; if (!valid_signal(data)) break; - clear_tsk_thread_flag(child, TIF_SYSCALL_EMU); + + if (request == PTRACE_SYSEMU_SINGLESTEP) + set_tsk_thread_flag(child, TIF_SYSCALL_EMU); + else + clear_tsk_thread_flag(child, TIF_SYSCALL_EMU); + clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE); set_singlestep(child); child->exit_code = data; @@ -686,7 +692,10 @@ void send_sigtrap(struct task_struct *ts __attribute__((regparm(3))) int do_syscall_trace(struct pt_regs *regs, int entryexit) { - int is_sysemu, is_singlestep, ret = 0; + int is_sysemu = test_thread_flag(TIF_SYSCALL_EMU), ret = 0; + /* With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP */ + int is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP); + /* do the secure computing check first */ secure_computing(regs->orig_eax); @@ -696,8 +705,11 @@ int do_syscall_trace(struct pt_regs *reg if (!(current->ptrace & PT_PTRACED)) goto out; - is_sysemu = test_thread_flag(TIF_SYSCALL_EMU); - is_singlestep = test_thread_flag(TIF_SINGLESTEP); + /* If a process stops on the 1st tracepoint with SYSCALL_TRACE + * and then is resumed with SYSEMU_SINGLESTEP, it will come in + * here. We have to check this and return */ + if (is_sysemu && entryexit) + return 0; /* Fake a debug trap */ if (is_singlestep) @@ -728,6 +740,7 @@ int do_syscall_trace(struct pt_regs *reg if (ret == 0) return 0; + regs->orig_eax = -1; /* force skip of syscall restarting */ if (unlikely(current->audit_context)) audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax); return 1; diff -puN include/linux/ptrace.h~uml-support-add-ptrace_sysemu_singlestep-option-to-i386 include/linux/ptrace.h --- devel/include/linux/ptrace.h~uml-support-add-ptrace_sysemu_singlestep-option-to-i386 2005-07-27 12:16:16.000000000 -0700 +++ devel-akpm/include/linux/ptrace.h 2005-07-27 12:16:16.000000000 -0700 @@ -21,6 +21,7 @@ #define PTRACE_SYSCALL 24 #define PTRACE_SYSEMU 31 +#define PTRACE_SYSEMU_SINGLESTEP 32 /* 0x4200-0x4300 are reserved for architecture-independent additions. */ #define PTRACE_SETOPTIONS 0x4200 _