On 11/17/17 9:25 AM, Oleg Nesterov wrote:
On 11/15, Yonghong Song wrote:
v3 -> v4:
. Revert most of v3 change as 32bit emulation is not really working
on x86_64 platform as among other issues, function emulate_push_stack()
needs to account for 32bit app on 64bit platform.
A separate effort is ongoing to address this issue.
Reviewed-by: Oleg Nesterov <o...@redhat.com>
Please test your patch with the fix below, in this particular case the
TIF_IA32 check should be fine. Although this is not what we really want,
we should probably use user_64bit_mode(regs) which checks ->cs. But this
needs more changes and doesn't solve other problems (get_unmapped_area)
so I still can't decide what should we do right now...
I tested the below change with my patch. On x86_64, both 64bit and 32bit
program can be uprobe emulated properly. On x86_32, however, there is a
compilation error like below:
In function ‘check_copy_size’,
inlined from ‘copy_to_user’ at
/home/yhs/work/tip/include/linux/uaccess.h:154:6,
inlined from ‘emulate_push_stack.isra.9’ at
/home/yhs/work/tip/arch/x86/kernel/uprobes.c:535:6:
/home/yhs/work/tip/include/linux/thread_info.h:139:4: error: call to
‘__bad_copy_from’ declared with attribute error: copy source size is too
small
__bad_copy_from();
Basically, test_thread_flag(TIF_IA32) returns 0 on x86_32 system.
Oleg.
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -516,7 +516,7 @@ struct uprobe_xol_ops {
static inline int sizeof_long(void)
{
- return in_ia32_syscall() ? 4 : 8;
+ return test_thread_flag(TIF_IA32) ? 4 : 8;
}
static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
