tools/nolibc: mips: shrink _start with _start_c

move most of the _start operations to _start_c(), include the
stackprotector initialization.

Also clean up the instructions in delayed slots.

Signed

tools/nolibc: mips: shrink _start with _start_c

move most of the _start operations to _start_c(), include the
stackprotector initialization.

Also clean up the instructions in delayed slots.

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

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tools/nolibc: remove the old sys_stat support

The statx manpage [1] shows that it has been supported from Linux 4.11
and glibc 2.28, the Linux support can be checked for all of the
architectures wit

tools/nolibc: remove the old sys_stat support

The statx manpage [1] shows that it has been supported from Linux 4.11
and glibc 2.28, the Linux support can be checked for all of the
architectures with this command:

$ git grep -r statx v4.11 arch/ include/uapi/asm-generic/unistd.h \
| grep -E "aarch64|arm|mips|s390|x86|:include/uapi"

Besides riscv and loongarch, all of the nolibc supported architectures
have added sys_statx from Linux v4.11. riscv is mainlined to v4.15,
loongarch is mainlined to v5.19, both of them use the generic unistd.h,
so, they have added sys_statx from their first mainline versions.

The current oldest stable branch is v4.14, only reserving sys_statx
still preserves compatibility with all of the supported stable branches,
So, let's remove the old arch related and dependent sys_stat support
completely.

This is friendly to the future new architecture porting.

[1]: https://man7.org/linux/man-pages/man2/statx.2.html

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

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tools/nolibc: fix up startup failures for -O0 under gcc < 11.1.0

As gcc doc [1] shows:

Most optimizations are completely disabled at -O0 or if an -O level is
not set on the command line, even i

tools/nolibc: fix up startup failures for -O0 under gcc < 11.1.0

As gcc doc [1] shows:

Most optimizations are completely disabled at -O0 or if an -O level is
not set on the command line, even if individual optimization flags are
specified.

Test result [2] shows, gcc>=11.1.0 deviates from the above description,
but before gcc 11.1.0, "-O0" still forcely uses frame pointer in the
_start function even if the individual optimize("omit-frame-pointer")
flag is specified.

The frame pointer related operations will change the stack pointer (e.g.
In x86_64, an extra "push %rbp" will be inserted at the beginning of
_start) and make it differs from the one we expected, as a result, break
the whole startup function.

To fix up this issue, as suggested by Thomas, the individual "Os" and
"omit-frame-pointer" optimize flags are used together on _start function
to disable frame pointer completely even if the -O0 is set on the
command line.

[1]: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
[2]: https://lore.kernel.org/lkml/20230714094723.140603-1-falcon@tinylab.org/

Suggested-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/lkml/34b21ba5-7b59-4b3b-9ed6-ef9a3a5e06f7@t-8ch.de/
Fixes: 7f8548589661 ("tools/nolibc: make compiler and assembler agree on the section around _start")
Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

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tools/nolibc: arch-*.h: add missing space after ','

Fix up such errors reported by scripts/checkpatch.pl:

ERROR: space required after that ',' (ctx:VxV)
#148: FILE: tools/include/nolibc/arc

tools/nolibc: arch-*.h: add missing space after ','

Fix up such errors reported by scripts/checkpatch.pl:

ERROR: space required after that ',' (ctx:VxV)
#148: FILE: tools/include/nolibc/arch-aarch64.h:148:
+void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) __no_stack_protector _start(void)
^

ERROR: space required after that ',' (ctx:VxV)
#148: FILE: tools/include/nolibc/arch-aarch64.h:148:
+void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) __no_stack_protector _start(void)
^

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

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tools/nolibc: add missing my_syscall6() for mips

It is able to pass the 6th argument like the 5th argument via the stack
for mips, let's add a new my_syscall6() now, see [1] for details:

The mips

tools/nolibc: add missing my_syscall6() for mips

It is able to pass the 6th argument like the 5th argument via the stack
for mips, let's add a new my_syscall6() now, see [1] for details:

The mips/o32 system call convention passes arguments 5 through 8 on
the user stack.

Both mmap() and pselect6() require my_syscall6().

[1]: https://man7.org/linux/man-pages/man2/syscall.2.html

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

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tools/nolibc: arch-mips.h: shrink with _NOLIBC_SYSCALL_CLOBBERLIST

my_syscall<N> share the same long clobber list, define a macro for them.

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-of

tools/nolibc: arch-mips.h: shrink with _NOLIBC_SYSCALL_CLOBBERLIST

my_syscall<N> share the same long clobber list, define a macro for them.

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

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toolc/nolibc: arch-*.h: clean up whitespaces after __asm__

replace "__asm__ volatile" with "__asm__ volatile" and insert necessary
whitespace before "\" to make sure the lines are aligned.

$ s

toolc/nolibc: arch-*.h: clean up whitespaces after __asm__

replace "__asm__ volatile" with "__asm__ volatile" and insert necessary
whitespace before "\" to make sure the lines are aligned.

$ sed -i -e 's/__asm__ volatile ( /__asm__ volatile ( /g' tools/include/nolibc/*.h

Note, arch-s390.h uses post-tab instead of post-whitespaces, must avoid
insert whitespace just before the tabs:

$ sed -i -e 's/__asm__ volatile (\t/__asm__ volatile (\t/g' tools/include/nolibc/arch-*.h

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

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tools/nolibc: arch-*.h: fix up code indent errors

More than 8 whitespaces of the code indent are replaced with "tab +
whitespaces" to fix up such errors reported by scripts/checkpatch.pl:

ERROR

tools/nolibc: arch-*.h: fix up code indent errors

More than 8 whitespaces of the code indent are replaced with "tab +
whitespaces" to fix up such errors reported by scripts/checkpatch.pl:

ERROR: code indent should use tabs where possible
#64: FILE: tools/include/nolibc/arch-mips.h:64:
+^I \$

ERROR: code indent should use tabs where possible
#72: FILE: tools/include/nolibc/arch-mips.h:72:
+^I "t0", "t1", "t2", "t3", "t4", "t5", "t6", "t7", "t8", "t9" \$

This command is used:

$ sed -i -e '/^\t* /{s/ /\t/g}' tools/include/nolibc/arch-*.h

Signed-off-by: Zhangjin Wu <falcon@tinylab.org>
Signed-off-by: Willy Tarreau <w@1wt.eu>

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tools/nolibc: fix segfaults on compilers without attribute no_stack_protector

Not all compilers, notably GCC < 10, have support for
__attribute__((no_stack_protector)).
Fall back to a mechanism that

tools/nolibc: fix segfaults on compilers without attribute no_stack_protector

Not all compilers, notably GCC < 10, have support for
__attribute__((no_stack_protector)).
Fall back to a mechanism that also works there.

Tested with GCC 9.5.0 from kernel.org crosstools.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc: add autodetection for stackprotector support

The stackprotector support in nolibc should be enabled iff it is also
enabled in the compiler.
Use the preprocessor defines added by gcc an

tools/nolibc: add autodetection for stackprotector support

The stackprotector support in nolibc should be enabled iff it is also
enabled in the compiler.
Use the preprocessor defines added by gcc and clang if stackprotector
support is enable to automatically do so in nolibc.

This completely removes the need for any user-visible API.

To avoid inlining the lengthy preprocessor check into every user
introduce a new header compiler.h that abstracts the logic away.

As the define NOLIBC_STACKPROTECTOR is now not user-relevant anymore
prefix it with an underscore.

Suggested-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/lkml/20230520133237.GA27501@1wt.eu/
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc: mips: add stackprotector support

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/nolibc: use C89 comment syntax

Most of nolibc is already using C89 comments.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul

tools/nolibc: use C89 comment syntax

Most of nolibc is already using C89 comments.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc: add auxiliary vector retrieval for mips

In the _start block we now iterate over envp to find the auxiliary
vector after the NULL. The pointer is saved into an _auxv variable
that is ma

tools/nolibc: add auxiliary vector retrieval for mips

In the _start block we now iterate over envp to find the auxiliary
vector after the NULL. The pointer is saved into an _auxv variable
that is marked as weak so that it's accessible from multiple units.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc: export environ as a weak symbol on mips

The environ is retrieved from the _start code and is easy to store at
this moment. Let's declare the variable weak and store the value into
it.

tools/nolibc: export environ as a weak symbol on mips

The environ is retrieved from the _start code and is easy to store at
this moment. Let's declare the variable weak and store the value into
it. By not being static it will be visible to all units. By being weak,
if some programs already declared it, they will continue to be able to
use it. This was tested with mips24kc (BE) both with environ inherited
from _start and extracted from envp.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc: remove local definitions of O_* flags for open/fcntl

The historic nolibc code did not include asm/fcntl.h and had to define
the various O_RDWR etc macros in each arch-specific file (si

tools/nolibc: remove local definitions of O_* flags for open/fcntl

The historic nolibc code did not include asm/fcntl.h and had to define
the various O_RDWR etc macros in each arch-specific file (since such
values differ between certain archs). This was found at least once to
induce bugs due to wrong definitions. Let's get rid of all of them and
include asm/nolibc.h from sys.h instead. This was verified to work
properly on all supported architectures.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc: make compiler and assembler agree on the section around _start

The out-of-block asm() statement carrying _start does not allow the
compiler to know what section the assembly code is be

tools/nolibc: make compiler and assembler agree on the section around _start

The out-of-block asm() statement carrying _start does not allow the
compiler to know what section the assembly code is being emitted to,
and there's no easy way to push/pop the current section and restore
it. It sometimes causes issues depending on the include files ordering
and compiler optimizations. For example if a variable is declared
immediately before the asm() block and another one after, the compiler
assumes that the current section is still .bss and doesn't re-emit it,
making the second variable appear inside the .text section instead.
Forcing .bss at the end of the _start block doesn't work either because
at certain optimizations the compiler may reorder blocks and will make
some real code appear just after this block.

A significant number of solutions were attempted, but many of them were
still sensitive to section reordering. In the end, the best way to make
sure the compiler and assembler agree on the current section is to place
this code inside a function. Here the function is directly called _start
and configured not to emit a frame-pointer, hence to have no prologue.
If some future architectures would still emit some prologue, another
working approach consists in naming the function differently and placing
the _start label inside the asm statement. But the current solution is
simpler.

It was tested with nolibc-test at -O,-O0,-O2,-O3,-Os for arm,arm64,i386,
mips,riscv,s390 and x86_64.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc: restore mips branch ordering in the _start block

Depending on the compiler used and the optimization options, the sbrk()
test was crashing, both on real hardware (mips-24kc) and in qem

tools/nolibc: restore mips branch ordering in the _start block

Depending on the compiler used and the optimization options, the sbrk()
test was crashing, both on real hardware (mips-24kc) and in qemu. One
such example is kernel.org toolchain in version 11.3 optimizing at -Os.

Inspecting the sys_brk() call shows the following code:

0040047c <sys_brk>:
40047c: 24020fcd li v0,4045
400480: 27bdffe0 addiu sp,sp,-32
400484: 0000000c syscall
400488: 27bd0020 addiu sp,sp,32
40048c: 10e00001 beqz a3,400494 <sys_brk+0x18>
400490: 00021023 negu v0,v0
400494: 03e00008 jr ra

It is obviously wrong, the "negu" instruction is placed in beqz's
delayed slot, and worse, there's no nop nor instruction after the
return, so the next function's first instruction (addiu sip,sip,-32)
will also be executed as part of the delayed slot that follows the
return.

This is caused by the ".set noreorder" directive in the _start block,
that applies to the whole program. The compiler emits code without the
delayed slots and relies on the compiler to swap instructions when this
option is not set. Removing the option would require to change the
startup code in a way that wouldn't make it look like the resulting
code, which would not be easy to debug. Instead let's just save the
default ordering before changing it, and restore it at the end of the
_start block. Now the code is correct:

0040047c <sys_brk>:
40047c: 24020fcd li v0,4045
400480: 27bdffe0 addiu sp,sp,-32
400484: 0000000c syscall
400488: 10e00002 beqz a3,400494 <sys_brk+0x18>
40048c: 27bd0020 addiu sp,sp,32
400490: 00021023 negu v0,v0
400494: 03e00008 jr ra
400498: 00000000 nop

Fixes: 66b6f755ad45 ("rcutorture: Import a copy of nolibc") #5.0
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc: Remove .global _start from the entry point code

Building with clang yields the following error:
```
<inline asm>:3:1: error: _start changed binding to STB_GLOBAL
.global _start
^

tools/nolibc: Remove .global _start from the entry point code

Building with clang yields the following error:
```
<inline asm>:3:1: error: _start changed binding to STB_GLOBAL
.global _start
^
1 error generated.
```
Make sure only specify one between `.global _start` and `.weak _start`.
Remove `.global _start`.

Cc: llvm@lists.linux.dev
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc: Replace `asm` with `__asm__`

Replace `asm` with `__asm__` to support compilation with -std flag.
Using `asm` with -std flag makes GCC think `asm()` is a function call
instead of an inl

tools/nolibc: Replace `asm` with `__asm__`

Replace `asm` with `__asm__` to support compilation with -std flag.
Using `asm` with -std flag makes GCC think `asm()` is a function call
instead of an inline assembly.

GCC doc says:

For the C language, the `asm` keyword is a GNU extension. When
writing C code that can be compiled with `-ansi` and the `-std`
options that select C dialects without GNU extensions, use
`__asm__` instead of `asm`.

Link: https://gcc.gnu.org/onlinedocs/gcc/Basic-Asm.html
Reported-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc/arch: mark the _start symbol as weak

By doing so we can link together multiple C files that have been compiled
with nolibc and which each have a _start symbol.

Signed-off-by: Willy Tar

tools/nolibc/arch: mark the _start symbol as weak

By doing so we can link together multiple C files that have been compiled
with nolibc and which each have a _start symbol.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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tools/nolibc/arch: split arch-specific code into individual files

In order to ease maintenance, this splits the arch-specific code into
one file per architecture. A common file "arch.h" is used to i

tools/nolibc/arch: split arch-specific code into individual files

In order to ease maintenance, this splits the arch-specific code into
one file per architecture. A common file "arch.h" is used to include the
right file among arch-* based on the detected architecture. Projects
which are already split per architecture could simply rename these
files to $arch/arch.h and get rid of the common arch.h. For this
reason, include guards were placed into each arch-specific file.

Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

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