Messages in this thread |  | | Subject | Re: [PATCH][v4] uprobes/x86: emulate push insns for uprobe on x86 | From | Yonghong Song <> | Date | Fri, 17 Nov 2017 10:12:55 -0800 |
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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 <oleg@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) >
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