x86/dumpstack: Fix x86_32 kernel_stack_pointer() previous stack access

[deliverable/linux.git] / arch / x86 / kernel / ptrace.c

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 600edd225e81147473342d66fb991b9cad870756..a1606eadd9ce84d452407d07694e67f72f905daa 100644 (file)
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -173,8 +173,8 @@ unsigned long kernel_stack_pointer(struct pt_regs *regs)
                return sp;
 
        prev_esp = (u32 *)(context);
-       if (prev_esp)
-               return (unsigned long)prev_esp;
+       if (*prev_esp)
+               return (unsigned long)*prev_esp;
 
        return (unsigned long)regs;
 }
@@ -923,15 +923,18 @@ static int putreg32(struct task_struct *child, unsigned regno, u32 value)
 
        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.
+                * Warning: bizarre corner case fixup here.  A 32-bit
+                * debugger setting orig_eax to -1 wants to disable
+                * syscall restart.  Make sure that the syscall
+                * restart code sign-extends orig_ax.  Also make sure
+                * we interpret the -ERESTART* codes correctly if
+                * loaded into regs->ax 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;
+                       task_thread_info(child)->status |= TS_I386_REGS_POKED;
                break;
 
        case offsetof(struct user32, regs.eflags):