linux-kernel - Re: [tip:x86/urgent] x86/vdso: Discard the __bug

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Date:	Tue, 24 Jun 2014 11:26:11 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Ingo Molnar <mingo@...nel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:x86/urgent] x86/vdso: Discard the __bug_table section

On 06/24/2014 11:19 AM, Andy Lutomirski wrote:
>>>
>>> One of the recent x86/urgent vdso commits causes this build failure:
>>>
>>>  Error: too many copied sections (max = 13)
>>
>> I can't reproduce this with your config, which suggestes a binutils
>> issue, which is annoying.  Can you tell me what version of ld you're
>> using and send me the output of:
>>
>> for i in arch/x86/vdso/*.so.dbg; do echo $i; eu-readelf -S $i; done
> 
> Ping!
> 
> The current state of this is obviously not so good, but I don't know
> how to proceed.
> 

We used to have this kind of problems with PHDRs, where ld would guess
how much space it would need, somehow guess wrong, and fall on its face.

I think we want to actually print the number that we are trying to copy
in addition to the maximum, and I also noticed the test looks wrong.
Thus I would like to propose the following patch as a diagnostic:

diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h
index f42e2ddc663d..94158e100f26 100644
--- a/arch/x86/vdso/vdso2c.h
+++ b/arch/x86/vdso/vdso2c.h
@@ -99,8 +99,9 @@ static void BITSFUNC(copy_section)(struct
BITSFUNC(fake_sections) *out,
        if (!copy)
                return;

-       if (out->count >= out->max_count)
-               fail("too many copied sections (max = %d)\n",
out->max_count);
+       if (out->count > out->max_count)
+               fail("too many copied sections (max = %d, need = %d)\n",
+                    out->max_count, out->count);

        if (in_idx == out->in_shstrndx)
                out->out_shstrndx = out->count;

Does anyone have any objection?  Andy, I presume I am correct that =>
should be > there?

	-hpa
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