From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Lutomirski Subject: [PATCH] x86, vdso: Fix vdso2c's special_pages error checking Date: Fri, 18 Jul 2014 10:21:59 -0700 Message-ID: References: <20140718150005.73db8eb9@canb.auug.org.au> Return-path: In-Reply-To: <20140718150005.73db8eb9@canb.auug.org.au> Sender: linux-kernel-owner@vger.kernel.org To: Stephen Rothwell , "H. Peter Anvin" Cc: Thomas Gleixner , Ingo Molnar , Peter Zijlstra , linux-next@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Lutomirski List-Id: linux-next.vger.kernel.org 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. Signed-off-by: Andy Lutomirski --- arch/x86/vdso/vdso2c.h | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h index fd57829..0224987 100644 --- a/arch/x86/vdso/vdso2c.h +++ b/arch/x86/vdso/vdso2c.h @@ -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); } -- 1.9.3