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Siddhesh Poyarekar 0ee2c886d6 kselftest: Minimise dependency of get_size on C library interfaces 
[ Upstream commit 6b64a650f0 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-02-24 08:34:37 +01:00
arch sparc: Add .exit.data section. 2020-02-24 08:34:37 +01:00
block block: fix 32 bit overflow in __blkdev_issue_discard() 2020-02-01 09:37:12 +00:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: api - Fix race condition in crypto_spawn_alg 2020-02-11 04:34:05 -08:00
Documentation PM / devfreq: Add new name attribute for sysfs 2020-02-05 14:43:34 +00:00
drivers clocksource/drivers/bcm2835_timer: Fix memory leak of timer 2020-02-24 08:34:37 +01:00
firmware Fix built-in early-load Intel microcode alignment 2020-01-23 08:21:29 +01:00
fs ext4: fix ext4_dax_read/write inode locking sequence for IOCB_NOWAIT 2020-02-24 08:34:35 +01:00
include RDMA/uverbs: Verify MR access flags 2020-02-14 16:33:23 -05:00
init fork: fix some -Wmissing-prototypes warnings 2019-12-05 09:21:04 +01:00
ipc ipc/msg.c: consolidate all xxxctl_down() functions 2020-02-11 04:33:55 -08:00
kernel cpu/hotplug, stop_machine: Fix stop_machine vs hotplug order 2020-02-24 08:34:35 +01:00
lib lib/test_kasan.c: fix memory leak in kmalloc_oob_krealloc_more() 2020-02-11 04:33:57 -08:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm/page_alloc.c: fix uninitialized memmaps on a partially populated last section 2020-02-11 04:34:18 -08:00
net net/sched: flower: add missing validation of TCA_FLOWER_FLAGS 2020-02-24 08:34:34 +01:00
samples samples/bpf: Don't try to remove user's homedir on clean 2020-02-11 04:34:05 -08:00
scripts scripts/find-unused-docs: Fix massive false positives 2020-02-11 04:34:01 -08:00
security tomoyo: Use atomic_t for statistics counter 2020-02-05 14:43:38 +00:00
sound ALSA: ctl: allow TLV read operation for callback type of element in locked case 2020-02-24 08:34:35 +01:00
tools kselftest: Minimise dependency of get_size on C library interfaces 2020-02-24 08:34:37 +01:00
usr kbuild: clean compressed initramfs image 2019-10-07 18:57:16 +02:00
virt KVM: arm64: pmu: Don't increment SW_INCR if PMCR.E is unset 2020-02-14 16:33:26 -05:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS USB: rio500: Remove Rio 500 kernel driver 2019-10-17 13:44:47 -07:00
Makefile Linux 4.19.105 2020-02-19 19:51:59 +01:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.