kernel_samsung_sm7125

jenna

Nick Desaulniers dbaeff8df9 lib/string.c: implement stpcpy LLVM implemented a recent "libcall optimization" that lowers calls to `sprintf(dest, "%s", str)` where the return value is used to `stpcpy(dest, str) - dest`. This generally avoids the machinery involved in parsing format strings. `stpcpy` is just like `strcpy` except it returns the pointer to the new tail of `dest`. This optimization was introduced into clang-12. Implement this so that we don't observe linkage failures due to missing symbol definitions for `stpcpy`. Similar to last year's fire drill with: commit 5f074f3e192f ("lib/string.c: implement a basic bcmp") The kernel is somewhere between a "freestanding" environment (no full libc) and "hosted" environment (many symbols from libc exist with the same type, function signature, and semantics). As H. Peter Anvin notes, there's not really a great way to inform the compiler that you're targeting a freestanding environment but would like to opt-in to some libcall optimizations (see pr/47280 below), rather than opt-out. Arvind notes, -fno-builtin-* behaves slightly differently between GCC and Clang, and Clang is missing many __builtin_* definitions, which I consider a bug in Clang and am working on fixing. Masahiro summarizes the subtle distinction between compilers justly: To prevent transformation from foo() into bar(), there are two ways in Clang to do that; -fno-builtin-foo, and -fno-builtin-bar. There is only one in GCC; -fno-buitin-foo. (Any difference in that behavior in Clang is likely a bug from a missing __builtin_* definition.) Masahiro also notes: We want to disable optimization from foo() to bar(), but we may still benefit from the optimization from foo() into something else. If GCC implements the same transform, we would run into a problem because it is not -fno-builtin-bar, but -fno-builtin-foo that disables that optimization. In this regard, -fno-builtin-foo would be more future-proof than -fno-built-bar, but -fno-builtin-foo is still potentially overkill. We may want to prevent calls from foo() being optimized into calls to bar(), but we still may want other optimization on calls to foo(). It seems that compilers today don't quite provide the fine grain control over which libcall optimizations pseudo-freestanding environments would prefer. Finally, Kees notes that this interface is unsafe, so we should not encourage its use. As such, I've removed the declaration from any header, but it still needs to be exported to avoid linkage errors in modules. Link: https://lkml.kernel.org/r/20200825140001.2941001-1-ndesaulniers@google.com Link: https://bugs.llvm.org/show_bug.cgi?id=47162 Link: https://bugs.llvm.org/show_bug.cgi?id=47280 Link: ClangBuiltLinux/linux#1126 Link: https://man7.org/linux/man-pages/man3/stpcpy.3.html Link: https://pubs.opengroup.org/onlinepubs/9699919799/functions/stpcpy.html Link: https://reviews.llvm.org/D85963 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Reported-by: Sami Tolvanen <samitolvanen@google.com> Tested-by: Nathan Chancellor <natechancellor@gmail.com> Suggested-by: Andy Lavr <andy.lavr@gmail.com> Suggested-by: Arvind Sankar <nivedita@alum.mit.edu> Suggested-by: Joe Perches <joe@perches.com> Suggested-by: Masahiro Yamada <masahiroy@kernel.org> Suggested-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: <stable@vger.kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Alexandru Ardelean <alexandru.ardelean@analog.com> Cc: Yury Norov <yury.norov@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au> Change-Id: Id6bf5e796fdab4dd421519b9136c6bd9cd7cbe42		2 years ago
Documentation	A525FXXS4BVA2	3 years ago
arch	A525FXXS4BVA2	3 years ago
block	A525FXXU4BUL8	3 years ago
certs	Import A525FXXU3AUG4	3 years ago
crypto	Import A525FXXU3AUG4	3 years ago
drivers	sm7125: input: touchscreen: fts5cu56a: Add sysfs to track FOD pressed state	2 years ago
firmware	A525FXXU4AUJ2	3 years ago
fs	A525FXXU4BUL8	3 years ago
include	lib/string.c: implement stpcpy	2 years ago
init	Import A525FXXU3AUG4	3 years ago
ipc	Import A525FXXU3AUG4	3 years ago
kernel	A525FXXU4BUL8	3 years ago
lib	lib/string.c: implement stpcpy	2 years ago
mm	A525FXXU4BUL8	3 years ago
net	A525FXXU4BUL8	3 years ago
samples	Import A525FXXU3AUG4	3 years ago
scripts	sm7125: dtc: Silence warnings by default.	3 years ago
security	A525FXXS4BVA2	3 years ago
sound	Import A525FXXU3AUG4	3 years ago
techpack	A525FXXU4BUL8	3 years ago
tools	A525FXXU4BUL8	3 years ago
usr	Import A525FXXU3AUG4	3 years ago
virt	Import A525FXXU3AUG4	3 years ago
.cocciconfig	…
.get_maintainer.ignore	…
.gitattributes	.gitattributes: set git diff driver for C source code files	8 years ago
.gitignore	sm7125: Don't ignore .bin firmware files	3 years ago
.mailmap	.mailmap: Add Maciej W. Rozycki's Imagination e-mail address	7 years ago
Android.mk	Android: Add empty Android.mk file	2 years ago
AndroidKernel.mk	Import A525FXXU3AUG4	3 years ago
Androidbp	Import A525FXXU3AUG4	3 years ago
COPYING	Import A525FXXU3AUG4	3 years ago
CREDITS	Import A525FXXU3AUG4	3 years ago
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MAINTAINERS	Import A525FXXU3AUG4	3 years ago
Makefile	Revert "scripts: gcc-wrapper: Use wrapper to check compiler warnings"	3 years ago
README	Import A525FXXU3AUG4	3 years ago
build.config.aarch64	Import A525FXXU3AUG4	3 years ago
build.config.common	Import A525FXXU3AUG4	3 years ago
build.config.cuttlefish.aarch64	Import A525FXXU3AUG4	3 years ago
build.config.cuttlefish.x86_64	Import A525FXXU3AUG4	3 years ago
build.config.goldfish.arm	Import A525FXXU3AUG4	3 years ago
build.config.goldfish.arm64	Import A525FXXU3AUG4	3 years ago
build.config.goldfish.mips	Import A525FXXU3AUG4	3 years ago
build.config.goldfish.mips64	Import A525FXXU3AUG4	3 years ago
build.config.goldfish.x86	Import A525FXXU3AUG4	3 years ago
build.config.goldfish.x86_64	Import A525FXXU3AUG4	3 years ago
build.config.x86_64	Import A525FXXU3AUG4	3 years ago
disable_dbgfs.sh	AndroidKernel: Disable debugfs for user builds	4 years ago
gen_headers_arm.bp	Import A525FXXU3AUG4	3 years ago
gen_headers_arm64.bp	Import A525FXXU3AUG4	3 years ago
kernel_headers.py	Import A525FXXU3AUG4	3 years ago
verity_dev_keys.x509	Import A525FXXU3AUG4	3 years ago

README

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

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.