linux-kernel - Re: [PATCH 8/9] x86/dumpstack: Save first regs set for the executive summary

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Date:   Fri, 16 Mar 2018 13:11:17 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     X86 ML <x86@...nel.org>, Andy Lutomirski <luto@...capital.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 8/9] x86/dumpstack: Save first regs set for the executive
 summary

On Fri, Mar 16, 2018 at 07:01:12AM -0500, Josh Poimboeuf wrote:
> Hm, the "Code: Bad RIP value" will always be shown for syscall regs,
> which will probably cause some unnecessary confusion/worry.  Should we
> just skip printing it for the "regs->ip < PAGE_OFFSET" case?

How about we remove that check altogether?

I mean, __copy_from_user_inatomic() by way of probe_kernel_read() should
be able to handle every address.

And if it doesn't, it says so:

        if (probe_kernel_read(opcodes, ip, OPCODE_BUFSIZE)) {
                pr_cont("Bad RIP value.\n");

And if we *can* print opcode bytes, why not do so? It is one more hint
when debugging, who knows, might prove useful...

Hmm?

-- 
Regards/Gruss,
    Boris.

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