diff options
| author | Vegard Nossum <vegard.nossum@gmail.com> | 2008-06-27 17:22:17 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-06-27 17:45:59 +0200 |
| commit | 9d8ad5d6c7fce31fd2c0fd4fe9977bda3e92e340 (patch) | |
| tree | 1760e6576072b880a9b1f9c07879a33cce5306f7 | |
| parent | 543cf4cb3fe6f6cae3651ba918b9c56200b257d0 (diff) | |
x86: don't destroy %rbp on kernel-mode faults
From the code:
"B stepping K8s sometimes report an truncated RIP for IRET exceptions
returning to compat mode. Check for these here too."
The code then proceeds to truncate the upper 32 bits of %rbp. This means
that when do_page_fault() is finally called, its prologue,
do_page_fault:
push %rbp
movl %rsp, %rbp
will put the truncated base pointer on the stack. This means that the
stack tracer will not be able to follow the base-pointer changes and
will see all subsequent stack frames as unreliable.
This patch changes the code to use a different register (%rcx) for the
checking and leaves %rbp untouched.
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 556a8df522a..fa1c9eb7f60 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -926,11 +926,11 @@ error_kernelspace: iret run with kernel gs again, so don't set the user space flag. B stepping K8s sometimes report an truncated RIP for IRET exceptions returning to compat mode. Check for these here too. */ - leaq irq_return(%rip),%rbp - cmpq %rbp,RIP(%rsp) + leaq irq_return(%rip),%rcx + cmpq %rcx,RIP(%rsp) je error_swapgs - movl %ebp,%ebp /* zero extend */ - cmpq %rbp,RIP(%rsp) + movl %ecx,%ecx /* zero extend */ + cmpq %rcx,RIP(%rsp) je error_swapgs cmpq $gs_change,RIP(%rsp) je error_swapgs |