From 7e08db3359c86c94918feb33a1182cd0ff3bb10b Mon Sep 17 00:00:00 2001 From: Noah Goldstein Date: Sun, 9 Jan 2022 16:02:28 -0600 Subject: [PATCH] x86: Fix __wcsncmp_evex in strcmp-evex.S [BZ# 28755] Fixes [BZ# 28755] for wcsncmp by redirecting length >= 2^56 to __wcscmp_evex. For x86_64 this covers the entire address range so any length larger could not possibly be used to bound `s1` or `s2`. test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass. Signed-off-by: Noah Goldstein --- sysdeps/x86_64/multiarch/strcmp-evex.S | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S index 1d971f3889..0cd939d5af 100644 --- a/sysdeps/x86_64/multiarch/strcmp-evex.S +++ b/sysdeps/x86_64/multiarch/strcmp-evex.S @@ -104,6 +104,16 @@ ENTRY (STRCMP) je L(char0) jb L(zero) # ifdef USE_AS_WCSCMP +# ifndef __ILP32__ + movq %rdx, %rcx + /* Check if length could overflow when multiplied by + sizeof(wchar_t). Checking top 8 bits will cover all potential + overflow cases as well as redirect cases where its impossible to + length to bound a valid memory region. In these cases just use + 'wcscmp'. */ + shrq $56, %rcx + jnz __wcscmp_evex +# endif /* Convert units: from wide to byte char. */ shl $2, %RDX_LP # endif