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authorAndy Lutomirski <luto@amacapital.net>2014-11-22 18:00:31 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-11-23 13:56:18 -0800
commitaf726f21ed8af2cdaa4e93098dc211521218ae65 (patch)
treed3546c0fe44e49d283ed3d0ced3b92873f28df34 /arch/x86/kernel/traps.c
parentfc14f9c1272f62c3e8d01300f52467c0d9af50f9 (diff)
downloadblackbird-op-linux-af726f21ed8af2cdaa4e93098dc211521218ae65.tar.gz
blackbird-op-linux-af726f21ed8af2cdaa4e93098dc211521218ae65.zip
x86_64, traps: Fix the espfix64 #DF fixup and rewrite it in C
There's nothing special enough about the espfix64 double fault fixup to justify writing it in assembly. Move it to C. This also fixes a bug: if the double fault came from an IST stack, the old asm code would return to a partially uninitialized stack frame. Fixes: 3891a04aafd668686239349ea58f3314ea2af86b Signed-off-by: Andy Lutomirski <luto@amacapital.net> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86/kernel/traps.c')
-rw-r--r--arch/x86/kernel/traps.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 0d0e922fafc1..819662746e23 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -259,6 +259,30 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code)
static const char str[] = "double fault";
struct task_struct *tsk = current;
+#ifdef CONFIG_X86_ESPFIX64
+ extern unsigned char native_irq_return_iret[];
+
+ /*
+ * If IRET takes a non-IST fault on the espfix64 stack, then we
+ * end up promoting it to a doublefault. In that case, modify
+ * the stack to make it look like we just entered the #GP
+ * handler from user space, similar to bad_iret.
+ */
+ if (((long)regs->sp >> PGDIR_SHIFT) == ESPFIX_PGD_ENTRY &&
+ regs->cs == __KERNEL_CS &&
+ regs->ip == (unsigned long)native_irq_return_iret)
+ {
+ struct pt_regs *normal_regs = task_pt_regs(current);
+
+ /* Fake a #GP(0) from userspace. */
+ memmove(&normal_regs->ip, (void *)regs->sp, 5*8);
+ normal_regs->orig_ax = 0; /* Missing (lost) #GP error code */
+ regs->ip = (unsigned long)general_protection;
+ regs->sp = (unsigned long)&normal_regs->orig_ax;
+ return;
+ }
+#endif
+
exception_enter();
/* Return not checked because double check cannot be ignored */
notify_die(DIE_TRAP, str, regs, error_code, X86_TRAP_DF, SIGSEGV);
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