linux_dsm_epyc7002/tools/testing
Siddhesh Poyarekar 6b64a650f0 kselftest: Minimise dependency of get_size on C library interfaces
It was observed[1] on arm64 that __builtin_strlen led to an infinite
loop in the get_size selftest.  This is because __builtin_strlen (and
other builtins) may sometimes result in a call to the C library
function.  The C library implementation of strlen uses an IFUNC
resolver to load the most efficient strlen implementation for the
underlying machine and hence has a PLT indirection even for static
binaries.  Because this binary avoids the C library startup routines,
the PLT initialization never happens and hence the program gets stuck
in an infinite loop.

On x86_64 the __builtin_strlen just happens to expand inline and avoid
the call but that is not always guaranteed.

Further, while testing on x86_64 (Fedora 31), it was observed that the
test also failed with a segfault inside write() because the generated
code for the write function in glibc seems to access TLS before the
syscall (probably due to the cancellation point check) and fails
because TLS is not initialised.

To mitigate these problems, this patch reduces the interface with the
C library to just the syscall function.  The syscall function still
sets errno on failure, which is undesirable but for now it only
affects cases where syscalls fail.

[1] https://bugs.linaro.org/show_bug.cgi?id=5479

Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>
Reported-by: Masami Hiramatsu <masami.hiramatsu@linaro.org>
Tested-by: Masami Hiramatsu <masami.hiramatsu@linaro.org>
Reviewed-by: Tim Bird <tim.bird@sony.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
2020-01-16 13:08:26 -07:00
..
fault-injection docs: fault-injection: convert docs to ReST and rename to *.rst 2019-06-14 14:21:07 -06:00
ktest ktest: Fix some typos in config-bisect.pl 2019-07-24 15:37:18 -04:00
kunit kunit/kunit_tool_test: Test '--build_dir' option run 2019-12-23 10:52:41 -07:00
nvdimm tools/testing/nvdimm: Fix mock support for ioremap 2019-12-11 17:11:10 -08:00
radix-tree Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 15:45:14 -07:00
scatterlist treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
selftests kselftest: Minimise dependency of get_size on C library interfaces 2020-01-16 13:08:26 -07:00
vsock treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 441 2019-06-05 17:37:17 +02:00