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[tsan] Fix "failed to intercept sysctlnametomib" on FreeBSD 

The sysctlnametomib function is called from __tsan::Initialize via
__sanitizer::internal_sysctlbyname (see stack trace below). This results
in a fatal error since sysctlnametomib has not been intercepted yet.
This patch allows internal_sysctlbyname to be called before
__tsan::Initialize() has completed. On FreeBSD >= 1300045 sysctlbyname()
is a real syscall, but for older versions it calls sysctlnametomib()
followed by sysctl(). To avoid calling the intercepted version, look up
the real sysctlnametomib() followed by internal_sysctl() if the
syscall is not available.

This reduces check-sanitizer failures from 62 to 11 for me.

==34433==FATAL: ThreadSanitizer: failed to intercept sysctlnametomib
    at /exports/users/alr48/sources/upstream-llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_termination.cpp:51
    name=0x7fffffffce10, namelenp=0x7fffffffce08)
    at /exports/users/alr48/sources/upstream-llvm-project/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:7908
    oldp=0x7fffffffcf2c, oldlenp=0x7fffffffcf20, newp=0x0, newlen=0)
    at /exports/users/alr48/sources/upstream-llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp:803
    at /exports/users/alr48/sources/upstream-llvm-project/compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp:2152
    at /exports/users/alr48/sources/upstream-llvm-project/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp:367
    fname=0x21c731 "readlink", pc=34366042556)
    at /exports/users/alr48/sources/upstream-llvm-project/compiler-rt/lib/tsan/rtl/tsan_interceptors_posix.cpp:255
    bufsiz=1024)
    at /exports/users/alr48/sources/upstream-llvm-project/compiler-rt/lib/tsan/../sanitizer_common/sanitizer_common_interceptors.inc:7151

Reviewed By: #sanitizers, vitalybuka

Differential Revision: https://reviews.llvm.org/D85292
This commit is contained in:
Alex Richardson 2020-09-01 10:46:35 +01:00
parent 32a8a10b42
commit 7be8682921
1 changed files with 23 additions and 5 deletions
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28
compiler-rt/lib/sanitizer_common/sanitizer_linux.cpp
View File

@ -800,11 +800,29 @@ int internal_sysctl(const int *name, unsigned int namelen, void *oldp,
#if SANITIZER_FREEBSD
int internal_sysctlbyname(const char *sname, void *oldp, uptr *oldlenp,
const void *newp, uptr newlen) {
static decltype(sysctlbyname) *real = nullptr;
if (!real)
real = (decltype(sysctlbyname) *)dlsym(RTLD_NEXT, "sysctlbyname");
CHECK(real);
return real(sname, oldp, (size_t *)oldlenp, newp, (size_t)newlen);
// Note: this function can be called during startup, so we need to avoid
// calling any interceptable functions. On FreeBSD >= 1300045 sysctlbyname()
// is a real syscall, but for older versions it calls sysctlnametomib()
// followed by sysctl(). To avoid calling the intercepted version and
// asserting if this happens during startup, call the real sysctlnametomib()
// followed by internal_sysctl() if the syscall is not available.
#ifdef SYS___sysctlbyname
return internal_syscall(SYSCALL(__sysctlbyname), sname,
internal_strlen(sname), oldp, (size_t *)oldlenp, newp,
(size_t)newlen);
#else
static decltype(sysctlnametomib) *real_sysctlnametomib = nullptr;
if (!real_sysctlnametomib)
real_sysctlnametomib =
(decltype(sysctlnametomib) *)dlsym(RTLD_NEXT, "sysctlnametomib");
CHECK(real_sysctlnametomib);
int oid[CTL_MAXNAME];
size_t len = CTL_MAXNAME;
if (real_sysctlnametomib(sname, oid, &len) == -1)
return (-1);
return internal_sysctl(oid, len, oldp, oldlenp, newp, newlen);
#endif
}
#endif
#endif