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Siddhesh Poyarekar 56953ccd7f kselftest: Minimise dependency of get_size on C library interfaces
[ Upstream commit 6b64a650f0b2ae3940698f401732988699eecf7a ]

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 08:36:28 +01:00
arch sparc: Add .exit.data section. 2020-02-24 08:36:27 +01:00
block
certs
crypto crypto: testmgr - don't try to decrypt uninitialized buffers 2020-02-14 16:34:18 -05:00
Documentation dt-bindings: iio: adc: ad7606: Fix wrong maxItems value 2020-02-14 16:34:19 -05:00
drivers drm/amd/display: Clear state after exiting fixed active VRR state 2020-02-24 08:36:28 +01:00
fs ext4: fix ext4_dax_read/write inode locking sequence for IOCB_NOWAIT 2020-02-24 08:36:24 +01:00
include raid6/test: fix a compilation error 2020-02-24 08:36:27 +01:00
init Revert "um: Enable CONFIG_CONSTRUCTORS" 2020-02-01 09:34:53 +00:00
ipc ipc/msg.c: consolidate all xxxctl_down() functions 2020-02-11 04:35:07 -08:00
kernel kernel/module: Fix memleak in module_add_modinfo_attrs() 2020-02-24 08:36:26 +01:00
lib lib/test_kasan.c: fix memory leak in kmalloc_oob_krealloc_more() 2020-02-11 04:35:14 -08:00
LICENSES
mm mm/mmu_gather: invalidate TLB correctly on batch allocation failure and flush 2020-02-11 04:35:42 -08:00
net net/sched: flower: add missing validation of TCA_FLOWER_FLAGS 2020-02-24 08:36:22 +01:00
samples samples/bpf: Xdp_redirect_cpu fix missing tracepoint attach 2020-02-11 04:35:29 -08:00
scripts scripts/find-unused-docs: Fix massive false positives 2020-02-11 04:35:23 -08:00
security selinux: fall back to ref-walk if audit is required 2020-02-14 16:34:20 -05:00
sound ALSA: ctl: allow TLV read operation for callback type of element in locked case 2020-02-24 08:36:24 +01:00
tools kselftest: Minimise dependency of get_size on C library interfaces 2020-02-24 08:36:28 +01:00
usr
virt KVM: arm64: Treat emulated TVAL TimerValue as a signed 32-bit integer 2020-02-14 16:34:18 -05:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS MAINTAINERS: correct entries for ISDN/mISDN section 2020-02-11 04:35:06 -08:00
Makefile Linux 5.4.21 2020-02-19 19:53:10 +01:00
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.

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.