Commit f12c1f90 authored Jul 30, 2014 by Andy Lutomirski Committed by Ingo Molnar Sep 24, 2014

x86/vdso: Fix vdso2c's special_pages[] error checking



Stephen Rothwell's compiler did something amazing: it unrolled a
loop, discovered that one iteration of that loop contained an
always-true test, and emitted a warning that will IMO only serve
to convince people to disable the warning.

That bogus warning caused me to wonder what prompted such an
absurdity from his compiler, and I discovered that the code in
question was, in fact, completely wrong -- I was looking things
up in the wrong array.

This affects 3.16 as well, but the only effect is to screw up
the error checking a bit.  vdso2c's output is unaffected.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/53d96ad5.80ywqrbs33ZBCQej%25akpm@linux-foundation.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent f3670394

arch/x86/vdso/vdso2c.h

+7 −5

Original line number	Diff line number	Diff line
		@@ -109,16 +109,18 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,

		/* Validate mapping addresses. */
		for (i = 0; i < sizeof(special_pages) / sizeof(special_pages[0]); i++) {
		if (!syms[i])
		INT_BITS symval = syms[special_pages[i]];

		if (!symval)
		continue; /* The mapping isn't used; ignore it. */

		if (syms[i] % 4096)
		if (symval % 4096)
		fail("%s must be a multiple of 4096\n",
		required_syms[i].name);
		if (syms[sym_vvar_start] > syms[i] + 4096)
		fail("%s underruns begin_vvar\n",
		if (symval + 4096 < syms[sym_vvar_start])
		fail("%s underruns vvar_start\n",
		required_syms[i].name);
		if (syms[i] + 4096 > 0)
		if (symval + 4096 > 0)
		fail("%s is on the wrong side of the vdso text\n",
		required_syms[i].name);
		}

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