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

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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>
This commit is contained in:
Andy Lutomirski 2014-07-30 14:59:49 -07:00 committed by Ingo Molnar
parent f3670394c2
commit f12c1f9002
1 changed files with 7 additions and 5 deletions
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12
arch/x86/vdso/vdso2c.h
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@ -109,16 +109,18 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
/* Validate mapping addresses. */ /* Validate mapping addresses. */
for (i = 0; i < sizeof(special_pages) / sizeof(special_pages[0]); i++) { 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. */ continue; /* The mapping isn't used; ignore it. */
if (syms[i] % 4096) if (symval % 4096)
fail("%s must be a multiple of 4096\n", fail("%s must be a multiple of 4096\n",
required_syms[i].name); required_syms[i].name);
if (syms[sym_vvar_start] > syms[i] + 4096) if (symval + 4096 < syms[sym_vvar_start])
fail("%s underruns begin_vvar\n", fail("%s underruns vvar_start\n",
required_syms[i].name); 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", fail("%s is on the wrong side of the vdso text\n",
required_syms[i].name); required_syms[i].name);
} }