kernel/linux.git/tools/include/nolibc, branch v6.7.3

tools/nolibc: add support for constructors and destructors

2023-10-12T19:14:16+00:00

With the startup code moved to C, implementing support for constructors and deconstructors is fairly easy to implement. Examples for code size impact: text data bss dec hex filename 21837 104 88 22029 560d nolibc-test.before 22135 120 88 22343 5747 nolibc-test.after 21970 104 88 22162 5692 nolibc-test.after-only-crt.h-changes The sections are defined by [0]. [0] https://refspecs.linuxfoundation.org/elf/gabi4+/ch5.dynamic.html Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://lore.kernel.org/lkml/20231007-nolibc-constructors-v2-1-ef84693efbc1@weissschuh.net/

tools/nolibc: automatically detect necessity to use pselect6

2023-10-12T19:14:13+00:00

We can automatically detect if pselect6 is needed or not from the kernel headers. This removes the need to manually specify it. Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://lore.kernel.org/r/20230917-nolibc-syscall-nr-v2-4-03863d509b9a@weissschuh.net

tools/nolibc: don't define new syscall number

2023-10-12T19:14:12+00:00

All symbols created by nolibc are also visible to user code. Syscall constants are expected to come from the kernel headers and should not be made up by nolibc. Refactor the logic to avoid defining syscall numbers. Also the new code is easier to understand. Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://lore.kernel.org/r/20230917-nolibc-syscall-nr-v2-3-03863d509b9a@weissschuh.net

tools/nolibc: avoid unused parameter warnings for ENOSYS fallbacks

2023-10-12T19:14:10+00:00

The ENOSYS fallback code does not use its functions parameters. This can lead to compiler warnings about unused parameters. Explicitly avoid these warnings. Signed-off-by: Thomas Weißschuh Acked-by: Willy Tarreau Link: https://lore.kernel.org/r/20230917-nolibc-syscall-nr-v2-2-03863d509b9a@weissschuh.net

tools/nolibc: string: Remove the `_nolibc_memcpy_up()` function

2023-10-12T19:14:03+00:00

This function is only called by memcpy(), there is no real reason to have this wrapper. Delete this function and move the code to memcpy() directly. Signed-off-by: Ammar Faizi Reviewed-by: Alviro Iskandar Setiawan Signed-off-by: Willy Tarreau Signed-off-by: Thomas Weißschuh

tools/nolibc: string: Remove the `_nolibc_memcpy_down()` function

2023-10-12T19:14:02+00:00

This nolibc internal function is not used. Delete it. It was probably supposed to handle memmove(), but today the memmove() has its own implementation. Signed-off-by: Ammar Faizi Reviewed-by: Alviro Iskandar Setiawan Signed-off-by: Willy Tarreau Signed-off-by: Thomas Weißschuh

tools/nolibc: x86-64: Use `rep stosb` for `memset()`

2023-10-12T19:14:00+00:00

Simplify memset() on the x86-64 arch. The x86-64 arch has a 'rep stosb' instruction, which can perform memset() using only a single instruction, given: %al = value (just like the second argument of memset()) %rdi = destination %rcx = length Before this patch: ``` 00000000000010c9 : 10c9: 48 89 f8 mov %rdi,%rax 10cc: 48 85 d2 test %rdx,%rdx 10cf: 74 0e je 10df 10d1: 31 c9 xor %ecx,%ecx 10d3: 40 88 34 08 mov %sil,(%rax,%rcx,1) 10d7: 48 ff c1 inc %rcx 10da: 48 39 ca cmp %rcx,%rdx 10dd: 75 f4 jne 10d3 10df: c3 ret ``` After this patch: ``` 0000000000001511 : 1511: 96 xchg %eax,%esi 1512: 48 89 d1 mov %rdx,%rcx 1515: 57 push %rdi 1516: f3 aa rep stos %al,%es:(%rdi) 1518: 58 pop %rax 1519: c3 ret ``` v2: - Use pushq %rdi / popq %rax (Alviro). - Use xchg %eax, %esi (Willy). Link: https://lore.kernel.org/lkml/ZO9e6h2jjVIMpBJP@1wt.eu Suggested-by: Alviro Iskandar Setiawan Suggested-by: Willy Tarreau Signed-off-by: Ammar Faizi Reviewed-by: Alviro Iskandar Setiawan Signed-off-by: Willy Tarreau Signed-off-by: Thomas Weißschuh

tools/nolibc: x86-64: Use `rep movsb` for `memcpy()` and `memmove()`

2023-10-12T19:13:56+00:00

Simplify memcpy() and memmove() on the x86-64 arch. The x86-64 arch has a 'rep movsb' instruction, which can perform memcpy() using only a single instruction, given: %rdi = destination %rsi = source %rcx = length Additionally, it can also handle the overlapping case by setting DF=1 (backward copy), which can be used as the memmove() implementation. Before this patch: ``` 00000000000010ab : 10ab: 48 89 f8 mov %rdi,%rax 10ae: 31 c9 xor %ecx,%ecx 10b0: 48 39 f7 cmp %rsi,%rdi 10b3: 48 83 d1 ff adc $0xffffffffffffffff,%rcx 10b7: 48 85 d2 test %rdx,%rdx 10ba: 74 25 je 10e1 10bc: 48 83 c9 01 or $0x1,%rcx 10c0: 48 39 f0 cmp %rsi,%rax 10c3: 48 c7 c7 ff ff ff ff mov $0xffffffffffffffff,%rdi 10ca: 48 0f 43 fa cmovae %rdx,%rdi 10ce: 48 01 cf add %rcx,%rdi 10d1: 44 8a 04 3e mov (%rsi,%rdi,1),%r8b 10d5: 44 88 04 38 mov %r8b,(%rax,%rdi,1) 10d9: 48 01 cf add %rcx,%rdi 10dc: 48 ff ca dec %rdx 10df: 75 f0 jne 10d1 10e1: c3 ret 00000000000010e2 : 10e2: 48 89 f8 mov %rdi,%rax 10e5: 48 85 d2 test %rdx,%rdx 10e8: 74 12 je 10fc 10ea: 31 c9 xor %ecx,%ecx 10ec: 40 8a 3c 0e mov (%rsi,%rcx,1),%dil 10f0: 40 88 3c 08 mov %dil,(%rax,%rcx,1) 10f4: 48 ff c1 inc %rcx 10f7: 48 39 ca cmp %rcx,%rdx 10fa: 75 f0 jne 10ec 10fc: c3 ret ``` After this patch: ``` // memmove is an alias for memcpy 000000000040133b : 40133b: 48 89 d1 mov %rdx,%rcx 40133e: 48 89 f8 mov %rdi,%rax 401341: 48 89 fa mov %rdi,%rdx 401344: 48 29 f2 sub %rsi,%rdx 401347: 48 39 ca cmp %rcx,%rdx 40134a: 72 03 jb 40134f 40134c: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi) 40134e: c3 ret 40134f: 48 8d 7c 0f ff lea -0x1(%rdi,%rcx,1),%rdi 401354: 48 8d 74 0e ff lea -0x1(%rsi,%rcx,1),%rsi 401359: fd std 40135a: f3 a4 rep movsb %ds:(%rsi),%es:(%rdi) 40135c: fc cld 40135d: c3 ret ``` v3: - Make memmove as an alias for memcpy (Willy). - Make the forward copy the likely case (Alviro). v2: - Fix the broken memmove implementation (David). Link: https://lore.kernel.org/lkml/20230902062237.GA23141@1wt.eu Link: https://lore.kernel.org/lkml/5a821292d96a4dbc84c96ccdc6b5b666@AcuMS.aculab.com Suggested-by: David Laight Signed-off-by: Ammar Faizi Signed-off-by: Willy Tarreau Signed-off-by: Thomas Weißschuh

tools/nolibc: add stdarg.h header

2023-10-12T19:13:52+00:00

This allows nolic to work with `-nostdinc` avoiding any reliance on system headers. The implementation has been lifted from musl libc 1.2.4. There is already an implementation of stdarg.h in include/linux/stdarg.h but that is GPL licensed and therefore not suitable for nolibc. The used compiler builtins have been validated to be at least available since GCC 4.1.2 and clang 3.0.0. Signed-off-by: Thomas Weißschuh Signed-off-by: Willy Tarreau

tools/nolibc: mark start_c as weak

2023-10-12T19:13:51+00:00

Otherwise the different instances of _start_c from each compilation unit will lead to linker errors: /usr/bin/ld: /tmp/ccSNvRqs.o: in function `_start_c': nolibc-test-foo.c:(.text.nolibc_memset+0x9): multiple definition of `_start_c'; /tmp/ccG25101.o:nolibc-test.c:(.text+0x1ea3): first defined here Fixes: 17336755150b ("tools/nolibc: add new crt.h with _start_c") Signed-off-by: Thomas Weißschuh Link: https://lore.kernel.org/lkml/20231012-nolibc-start_c-multiple-v1-1-fbfc73e0283f@weissschuh.net/ Link: https://lore.kernel.org/lkml/20231012-nolibc-linkage-test-v1-1-315e682768b4@weissschuh.net/ Acked-by: Willy Tarreau