From: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
This is simply an adjustment for "Ptrace - i386: fix Syscall Audit interaction
with singlestep" to work on top of SYSEMU patches, too. On this patch, I have
some doubts: I wonder why we need to alter that way ptrace_disable().
I left the patch this way because it has been extensively tested, but I don't
understand the reason.
The current PTRACE_DETACH handling simply clears child->ptrace; actually this
is not enough because entry.S just looks at the thread_flags; actually,
do_syscall_trace checks current->ptrace but I don't think depending on that is
good, at least for performance, so I think the clearing is done elsewhere.
For instance, on PTRACE_CONT it's done, but doing PTRACE_DETACH without
PTRACE_CONT is possible (and happens when gdb crashes and one kills it
manually).
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
CC: Roland McGrath <roland@redhat.com>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
arch/i386/kernel/ptrace.c | 23 ++++++++++++++++++++---
1 files changed, 20 insertions(+), 3 deletions(-)
diff -puN arch/i386/kernel/ptrace.c~sysemu-fix-sysaudit--singlestep-interaction arch/i386/kernel/ptrace.c
--- devel/arch/i386/kernel/ptrace.c~sysemu-fix-sysaudit--singlestep-interaction 2005-08-21 23:48:28.000000000 -0700
+++ devel-akpm/arch/i386/kernel/ptrace.c 2005-08-21 23:48:28.000000000 -0700
@@ -271,6 +271,8 @@ static void clear_singlestep(struct task
void ptrace_disable(struct task_struct *child)
{
clear_singlestep(child);
+ clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+ clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
}
/*
@@ -663,14 +665,29 @@ __attribute__((regparm(3)))
int do_syscall_trace(struct pt_regs *regs, int entryexit)
{
int is_sysemu = test_thread_flag(TIF_SYSCALL_EMU), ret = 0;
- /* With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP */
+ /* With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP for syscall
+ * interception. */
int is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP);
/* do the secure computing check first */
secure_computing(regs->orig_eax);
- if (unlikely(current->audit_context) && entryexit)
- audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
+ if (unlikely(current->audit_context)) {
+ if (entryexit)
+ audit_syscall_exit(current, AUDITSC_RESULT(regs->eax), regs->eax);
+ /* Debug traps, when using PTRACE_SINGLESTEP, must be sent only
+ * on the syscall exit path. Normally, when TIF_SYSCALL_AUDIT is
+ * not used, entry.S will call us only on syscall exit, not
+ * entry; so when TIF_SYSCALL_AUDIT is used we must avoid
+ * calling send_sigtrap() on syscall entry.
+ *
+ * Note that when PTRACE_SYSEMU_SINGLESTEP is used,
+ * is_singlestep is false, despite his name, so we will still do
+ * the correct thing.
+ */
+ else if (is_singlestep)
+ goto out;
+ }
if (!(current->ptrace & PT_PTRACED))
goto out;
_