linux-kernel - Re: [PATCH][v4] uprobes/x86: emulate push insns for uprobe on x86

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Message-ID: <20171117172526.GA10949@redhat.com>
Date:   Fri, 17 Nov 2017 18:25:26 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Yonghong Song <yhs@...com>
Cc:     mingo@...nel.org, tglx@...utronix.de, peterz@...radead.org,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        netdev@...r.kernel.org, ast@...com, kernel-team@...com
Subject: Re: [PATCH][v4] uprobes/x86: emulate push insns for uprobe on x86

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@...hat.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...

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)