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@@ -509,15 +509,27 @@ asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
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}
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break;
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+ case PTRACE_SYSEMU: /* continue and stop at next syscall, which will not be executed */
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case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
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case PTRACE_CONT: /* restart after signal. */
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ret = -EIO;
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if (!valid_signal(data))
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break;
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+ /* If we came here with PTRACE_SYSEMU and now continue with
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+ * PTRACE_SYSCALL, entry.S used to intercept the syscall return.
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+ * But it shouldn't!
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+ * So we don't clear TIF_SYSCALL_EMU, which is always unused in
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+ * this special case, to remember, we came from SYSEMU. That
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+ * flag will be cleared by do_syscall_trace().
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+ */
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+ if (request == PTRACE_SYSEMU) {
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+ set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
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+ } else if (request == PTRACE_CONT) {
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+ clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
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+ }
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if (request == PTRACE_SYSCALL) {
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set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
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- }
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- else {
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+ } else {
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clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
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}
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child->exit_code = data;
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@@ -546,6 +558,8 @@ asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
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ret = -EIO;
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if (!valid_signal(data))
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break;
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+ /*See do_syscall_trace to know why we don't clear
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+ * TIF_SYSCALL_EMU.*/
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clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
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set_singlestep(child);
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child->exit_code = data;
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@@ -678,37 +692,43 @@ void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
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* - triggered by current->work.syscall_trace
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*/
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__attribute__((regparm(3)))
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-void do_syscall_trace(struct pt_regs *regs, int entryexit)
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+int do_syscall_trace(struct pt_regs *regs, int entryexit)
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{
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+ int is_sysemu, is_systrace, is_singlestep, ret = 0;
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/* do the secure computing check first */
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secure_computing(regs->orig_eax);
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- if (unlikely(current->audit_context)) {
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- if (entryexit)
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- audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
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-
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- /* Debug traps, when using PTRACE_SINGLESTEP, must be sent only
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- * on the syscall exit path. Normally, when TIF_SYSCALL_AUDIT is
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- * not used, entry.S will call us only on syscall exit, not
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- * entry ; so when TIF_SYSCALL_AUDIT is used we must avoid
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- * calling send_sigtrap() on syscall entry.
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- */
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- else if (is_singlestep)
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- goto out;
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- }
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+ if (unlikely(current->audit_context) && entryexit)
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+ audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
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if (!(current->ptrace & PT_PTRACED))
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goto out;
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+ is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
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+ is_systrace = test_thread_flag(TIF_SYSCALL_TRACE);
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+ is_singlestep = test_thread_flag(TIF_SINGLESTEP);
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+
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+ /* We can detect the case of coming from PTRACE_SYSEMU and now running
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+ * with PTRACE_SYSCALL or PTRACE_SINGLESTEP, by TIF_SYSCALL_EMU being
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+ * set additionally.
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+ * If so let's reset the flag and return without action (no singlestep
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+ * nor syscall tracing, since no actual step has been executed).
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+ */
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+ if (is_sysemu && (is_systrace || is_singlestep)) {
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+ clear_thread_flag(TIF_SYSCALL_EMU);
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+ goto out;
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+ }
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+
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/* Fake a debug trap */
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if (test_thread_flag(TIF_SINGLESTEP))
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send_sigtrap(current, regs, 0);
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- if (!test_thread_flag(TIF_SYSCALL_TRACE))
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+ if (!is_systrace && !is_sysemu)
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goto out;
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/* the 0x80 provides a way for the tracing parent to distinguish
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between a syscall stop and SIGTRAP delivery */
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+ /* Note that the debugger could change the result of test_thread_flag!*/
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ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
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/*
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@@ -720,9 +740,10 @@ void do_syscall_trace(struct pt_regs *regs, int entryexit)
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send_sig(current->exit_code, current, 1);
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current->exit_code = 0;
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}
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+ ret = is_sysemu;
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out:
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if (unlikely(current->audit_context) && !entryexit)
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audit_syscall_entry(current, AUDIT_ARCH_I386, regs->orig_eax,
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regs->ebx, regs->ecx, regs->edx, regs->esi);
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-
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+ return ret;
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}
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Laurent Vivier