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libc: Disable ASAN for certain string functions

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They deliberately read out-of-bounds values to avoid byte-by-byte
loads and check multiple bytes at once. While this will work on x86,
it is flagged as an out-of-bounds read with ASAN, so we have to
disable instrumentation here. This also causes bounds errors for CHERI,
so in CheriBSD we use implementations that avoid OOB reads.

Differential Revision: https://reviews.freebsd.org/D31045
This commit is contained in:
Alex Richardson 2021-08-02 09:51:34 +01:00
parent f0712132b6
commit 8185be3307
1 changed files with 9 additions and 0 deletions
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9
lib/libc/string/Makefile.inc
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@ -29,6 +29,15 @@ MISRCS+=bcmp.c bcopy.c bzero.c explicit_bzero.c \
SYM_MAPS+= ${LIBC_SRCTOP}/string/Symbol.map
.if ${MK_ASAN} != "no"
# These source files deliberately read out of bounds since they assume that
# out-of-bounds memory accesses that don't cross pages are always legal.
# Note: While this is fine on x86, it does break when running with CHERI.
CFLAGS.strlen.c+= -fno-sanitize=address
CFLAGS.strchrnul.c+= -fno-sanitize=address
CFLAGS.memchr.c+= -fno-sanitize=address
.endif
# machine-dependent string sources
.sinclude "${LIBC_SRCTOP}/${LIBC_ARCH}/string/Makefile.inc"