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authorRoland McGrath <roland@redhat.com>2009-09-22 20:12:07 -0700
committerRoland McGrath <roland@redhat.com>2009-09-22 22:49:24 -0700
commit8cb3ed13935b9b523c2de7afc8f68473fe1d4531 (patch)
tree8c9d53ac4e9facc5750cc6bd7bd07260845b9797 /arch/x86
parent08ff18e299b1a1c91f4911fe9f35c4550218c73f (diff)
x86: ptrace: set TS_COMPAT when 32-bit ptrace sets orig_eax>=0
The 32-bit ptrace syscall on a 64-bit kernel (32-bit debugger on 32-bit task) behaves differently than a native 32-bit kernel. When setting a register state of orig_eax>=0 and eax=-ERESTART* when the debugged task is NOT on its way out of a 32-bit syscall, the task will fail to do the syscall restart logic that it should do. Test case available at http://sources.redhat.com/cgi-bin/cvsweb.cgi/~checkout~/tests/ptrace-tests/tests/erestartsys-trap.c?cvsroot=systemtap This happens because the 32-bit ptrace syscall sets eax=0xffffffff when it sets orig_eax>=0. The resuming task will not sign-extend this for the -ERESTART* check because TS_COMPAT is not set. (So the task thinks it is restarting after a 64-bit syscall, not a 32-bit one.) The fix is to have 32-bit ptrace calls set TS_COMPAT when setting orig_eax>=0. This ensures that the 32-bit syscall restart logic will apply when the child resumes. Signed-off-by: Roland McGrath <roland@redhat.com>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/ptrace.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 52222fab99f..7b058a2dc66 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -1111,10 +1111,22 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 value)
R32(esi, si);
R32(ebp, bp);
R32(eax, ax);
- R32(orig_eax, orig_ax);
R32(eip, ip);
R32(esp, sp);
+ case offsetof(struct user32, regs.orig_eax):
+ /*
+ * A 32-bit debugger setting orig_eax means to restore
+ * the state of the task restarting a 32-bit syscall.
+ * Make sure we interpret the -ERESTART* codes correctly
+ * in case the task is not actually still sitting at the
+ * exit from a 32-bit syscall with TS_COMPAT still set.
+ */
+ regs->orig_ax = value;
+ if (syscall_get_nr(child, regs) >= 0)
+ task_thread_info(child)->status |= TS_COMPAT;
+ break;
+
case offsetof(struct user32, regs.eflags):
return set_flags(child, value);