[PATCH] Uml support: reorganize PTRACE_SYSEMU support

With this patch, we change the way we handle switching from PTRACE_SYSEMU to
PTRACE_{SINGLESTEP,SYSCALL}, to free TIF_SYSCALL_EMU from double use as a
preparation for PTRACE_SYSEMU_SINGLESTEP extension, without changing the
behavior of the host kernel.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 14 insertions, 29 deletions

diff --git a/arch/i386/kernel/ptrace.c b/arch/i386/kernel/ptrace.c
index 5b569dc1c227..18642f05dde1 100644
--- a/arch/i386/kernel/ptrace.c
+++ b/arch/i386/kernel/ptrace.c
@@ -515,21 +515,14 @@ asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
                 ret = -EIO;
                 if (!valid_signal(data))
                         break;
-                /* If we came here with PTRACE_SYSEMU and now continue with
-                 * PTRACE_SYSCALL, entry.S used to intercept the syscall return.
-                 * But it shouldn't!
-                 * So we don't clear TIF_SYSCALL_EMU, which is always unused in
-                 * this special case, to remember, we came from SYSEMU. That
-                 * flag will be cleared by do_syscall_trace().
-                 */
                 if (request == PTRACE_SYSEMU) {
                         set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
-                } else if (request == PTRACE_CONT) {
-                        clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
-                }
-                if (request == PTRACE_SYSCALL) {
+                        clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+                } else if (request == PTRACE_SYSCALL) {
                         set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+                        clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
                 } else {
+                        clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
                         clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                 }
                 child->exit_code = data;
@@ -558,8 +551,7 @@ asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
                 ret = -EIO;
                 if (!valid_signal(data))
                         break;
-                /*See do_syscall_trace to know why we don't clear
-                 * TIF_SYSCALL_EMU.*/
+                clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
                 clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                 set_singlestep(child);
                 child->exit_code = data;
@@ -694,7 +686,7 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
 __attribute__((regparm(3)))
 int do_syscall_trace(struct pt_regs *regs, int entryexit)
 {
-        int is_sysemu, is_systrace, is_singlestep, ret = 0;
+        int is_sysemu, is_singlestep, ret = 0;
         /* do the secure computing check first */
         secure_computing(regs->orig_eax);
 
@@ -705,25 +697,13 @@ int do_syscall_trace(struct pt_regs *regs, int entryexit)
                 goto out;
 
         is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
-        is_systrace = test_thread_flag(TIF_SYSCALL_TRACE);
         is_singlestep = test_thread_flag(TIF_SINGLESTEP);
 
-        /* We can detect the case of coming from PTRACE_SYSEMU and now running
-         * with PTRACE_SYSCALL or PTRACE_SINGLESTEP, by TIF_SYSCALL_EMU being
-         * set additionally.
-         * If so let's reset the flag and return without action (no singlestep
-         * nor syscall tracing, since no actual step has been executed).
-         */
-        if (is_sysemu && (is_systrace || is_singlestep)) {
-                clear_thread_flag(TIF_SYSCALL_EMU);
-                goto out;
-        }
-
         /* Fake a debug trap */
-        if (test_thread_flag(TIF_SINGLESTEP))
+        if (is_singlestep)
                 send_sigtrap(current, regs, 0);
 
-        if (!is_systrace && !is_sysemu)
+        if (!test_thread_flag(TIF_SYSCALL_TRACE) && !is_sysemu)
                 goto out;
 
         /* the 0x80 provides a way for the tracing parent to distinguish
@@ -745,5 +725,10 @@ int do_syscall_trace(struct pt_regs *regs, int entryexit)
         if (unlikely(current->audit_context) && !entryexit)
                 audit_syscall_entry(current, AUDIT_ARCH_I386, regs->orig_eax,
                                     regs->ebx, regs->ecx, regs->edx, regs->esi);
-        return ret;
+        if (ret == 0)
+                return 0;
+
+        if (unlikely(current->audit_context))
+                audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
+        return 1;
 }