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nolibc changes for v7.3

Browse Source 
Highlights:
 * New architectures: Alpha
 * New library functionality: readlink(), getcwd()
 * Various bugfixes and cleanups
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Merge tag 'nolibc-20260814-for-7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/nolibc/linux-nolibc

Pull nolibc updates from Thomas Weißschuh:

 - New architecture: Alpha

 - New library functionality: readlink(), getcwd()

 - Various bugfixes and cleanups

* tag 'nolibc-20260814-for-7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/nolibc/linux-nolibc:
  tools/nolibc: add support for Alpha
  tools/nolibc/powerpc: mark ctr and xer as clobbered by system call
  tools/nolibc: remove dead __ARCH_WANT_SYS_OLD_SELECT
  selftests/nolibc: add debug information
  tools/nolibc: mark arg1 operand in __nolibc_syscall0() as write-only
  selftests/nolibc: Add test for getcwd() and readlink()
  tools/nolibc: unistd: Add readlink()
  tools/nolibc: unistd: Add getcwd()
This commit is contained in:
Linus Torvalds 2026-08-18 10:50:44 -07:00
commit 2063dd9d0b
12 changed files with 284 additions and 11 deletions
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2
tools/include/nolibc/Makefile
View File

@ -17,7 +17,7 @@ endif
# it defaults to this nolibc directory.
OUTPUT ?= $(CURDIR)/
architectures := arm arm64 loongarch m68k mips openrisc parisc powerpc riscv s390 sh sparc x86
architectures := alpha arm arm64 loongarch m68k mips openrisc parisc powerpc riscv s390 sh sparc x86
arch_files := arch.h $(addsuffix .h, $(addprefix arch-, $(architectures)))
all_files := \
alloca.h \

159
tools/include/nolibc/arch-alpha.h Normal file
View File

@ -0,0 +1,159 @@
/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
/*
* Alpha specific definitions for NOLIBC
* Copyright (C) 2025 Thomas Weißschuh <linux@weissschuh.net>
*/
#ifndef _NOLIBC_ARCH_ALPHA_H
#define _NOLIBC_ARCH_ALPHA_H
#include "compiler.h"
#include "crt.h"
/*
* Syscalls for Alpha:
* - registers are 64-bit
* - syscall number is passed in $0/v0
* - the system call is performed by calling callsys
* - syscall return comes in $0/v0, error flag in $19/a3
* - arguments are passed in $16/a0 to $21/a5
* - GCC does not support symbol register names
*/
#define _NOLIBC_SYSCALL_CLOBBERLIST \
"$1", "$2", "$3", "$4", "$5", "$6", "$7", "$8", \
"$22", "$23", "$24", "$25", "$27", "$28", "memory", "cc"
#define __nolibc_syscall0(num) \
({ \
register long _num __asm__ ("$0") = (num); \
register long _err __asm__ ("$19"); \
\
__asm__ volatile ( \
"callsys" \
: "+r"(_num), "=r"(_err) \
: \
: _NOLIBC_SYSCALL_CLOBBERLIST, \
"$16", "$17", "$18", "$20", "$21" \
); \
_err ? -_num : _num; \
})
#define __nolibc_syscall1(num, arg1) \
({ \
register long _num __asm__ ("$0") = (num); \
register long _err __asm__ ("$19"); \
register long _arg1 __asm__ ("$16") = (long)(arg1); \
\
__asm__ volatile ( \
"callsys" \
: "+r"(_num), "=r"(_err) \
: "r"(_arg1) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "$17", "$18", "$20", "$21" \
); \
_err ? -_num : _num; \
})
#define __nolibc_syscall2(num, arg1, arg2) \
({ \
register long _num __asm__ ("$0") = (num); \
register long _err __asm__ ("$19"); \
register long _arg1 __asm__ ("$16") = (long)(arg1); \
register long _arg2 __asm__ ("$17") = (long)(arg2); \
\
__asm__ volatile ( \
"callsys" \
: "+r"(_num), "=r"(_err) \
: "r"(_arg1), "r"(_arg2) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "$18", "$20", "$21" \
); \
_err ? -_num : _num; \
})
#define __nolibc_syscall3(num, arg1, arg2, arg3) \
({ \
register long _num __asm__ ("$0") = (num); \
register long _err __asm__ ("$19"); \
register long _arg1 __asm__ ("$16") = (long)(arg1); \
register long _arg2 __asm__ ("$17") = (long)(arg2); \
register long _arg3 __asm__ ("$18") = (long)(arg3); \
\
__asm__ volatile ( \
"callsys" \
: "+r"(_num), "=r"(_err) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "$20", "$21" \
); \
_err ? -_num : _num; \
})
#define __nolibc_syscall4(num, arg1, arg2, arg3, arg4) \
({ \
register long _num __asm__ ("$0") = (num); \
register long _arg1 __asm__ ("$16") = (long)(arg1); \
register long _arg2 __asm__ ("$17") = (long)(arg2); \
register long _arg3 __asm__ ("$18") = (long)(arg3); \
register long _arg4 __asm__ ("$19") = (long)(arg4); \
\
__asm__ volatile ( \
"callsys" \
: "+r"(_num), "+r"(_arg4) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "$20", "$21" \
); \
_arg4 ? -_num : _num; \
})
#define __nolibc_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
({ \
register long _num __asm__ ("$0") = (num); \
register long _arg1 __asm__ ("$16") = (long)(arg1); \
register long _arg2 __asm__ ("$17") = (long)(arg2); \
register long _arg3 __asm__ ("$18") = (long)(arg3); \
register long _arg4 __asm__ ("$19") = (long)(arg4); \
register long _arg5 __asm__ ("$20") = (long)(arg5); \
\
__asm__ volatile ( \
"callsys" \
: "+r"(_num), "+r"(_arg4) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg5) \
: _NOLIBC_SYSCALL_CLOBBERLIST, "$21" \
); \
_arg4 ? -_num : _num; \
})
#define __nolibc_syscall6(num, arg1, arg2, arg3, arg4, arg5, arg6) \
({ \
register long _num __asm__ ("$0") = (num); \
register long _arg1 __asm__ ("$16") = (long)(arg1); \
register long _arg2 __asm__ ("$17") = (long)(arg2); \
register long _arg3 __asm__ ("$18") = (long)(arg3); \
register long _arg4 __asm__ ("$19") = (long)(arg4); \
register long _arg5 __asm__ ("$20") = (long)(arg5); \
register long _arg6 __asm__ ("$21") = (long)(arg6); \
\
__asm__ volatile ( \
"callsys" \
: "+r"(_num), "+r"(_arg4) \
: "r"(_arg1), "r"(_arg2), "r"(_arg3), "r"(_arg5), \
"r"(_arg6) \
: _NOLIBC_SYSCALL_CLOBBERLIST \
); \
_arg4 ? -_num : _num; \
})
/* startup code */
void __attribute__((weak, noreturn)) __nolibc_entrypoint __nolibc_no_stack_protector
_start(void)
{
__asm__ volatile (
"br $gp, 0f\n" /* setup $gp, so that 'lda' works */
"0: ldgp $gp, 0($gp)\n"
"lda $27, _start_c\n" /* setup current function address for _start_c */
"mov $sp, $16\n" /* save argc pointer to $16, as arg1 of _start_c */
"br _start_c\n" /* transfer to c runtime */
);
__nolibc_entrypoint_epilogue();
}
#endif /* _NOLIBC_ARCH_ALPHA_H */

3
tools/include/nolibc/arch-arm.h
View File

@ -33,10 +33,7 @@
* with r7 before calling svc, and r6 is marked as clobbered.
* We're just using any regular register which we assign to r7 after saving
* it.
*
* Also, ARM supports the old_select syscall if newselect is not available
*/
#define __ARCH_WANT_SYS_OLD_SELECT
#if (defined(__THUMBEB__) || defined(__THUMBEL__)) && \
!defined(NOLIBC_OMIT_FRAME_POINTER)

2
tools/include/nolibc/arch-powerpc.h
View File

@ -26,7 +26,7 @@
*/
#define _NOLIBC_SYSCALL_CLOBBERLIST \
"memory", "cr0", "r12", "r11", "r10", "r9"
"memory", "cr0", "ctr", "xer", "r12", "r11", "r10", "r9"
#define __nolibc_syscall0(num) \
({ \

2
tools/include/nolibc/arch-sparc.h
View File

@ -45,7 +45,7 @@
\
__asm__ volatile ( \
_NOLIBC_SYSCALL \
: "+r"(_arg1) \
: "=r"(_arg1) \
: "r"(_num) \
: "memory", "cc" \
); \

3
tools/include/nolibc/arch-x86.h
View File

@ -25,10 +25,7 @@
* don't have to experience issues with register constraints.
* - the syscall number is always specified last in order to allow to force
* some registers before (gcc refuses a %-register at the last position).
*
* Also, i386 supports the old_select syscall if newselect is not available
*/
#define __ARCH_WANT_SYS_OLD_SELECT
#define __nolibc_syscall0(num) \
({ \

2
tools/include/nolibc/arch.h
View File

@ -32,6 +32,8 @@
#include "arch-openrisc.h"
#elif defined(__hppa__)
#include "arch-parisc.h"
#elif defined(__alpha__)
#include "arch-alpha.h"
#else
#error Unsupported Architecture
#endif

58
tools/include/nolibc/unistd.h
View File

@ -73,6 +73,48 @@ int ftruncate(int fd, off_t length)
return __sysret(_sys_ftruncate(fd, length));
}
/*
* char *getcwd(char *buf, size_t size);
*/
static __attribute__((unused))
int _sys_getcwd(char *buf, size_t size)
{
return __nolibc_syscall2(__NR_getcwd, buf, size);
}
static __attribute__((unused))
char *getcwd(char *buf, size_t size)
{
int ret;
/* Unlike other libc's we don't handle passing NULL for buf */
if (!buf || !size) {
SET_ERRNO(EINVAL);
return NULL;
}
ret = __sysret(_sys_getcwd(buf, size));
/* On error return NULL, __sysret() above will have set errno */
if (ret < 0)
return NULL;
/* Handle no path being written or the kernel putting
* "(unreachable)" into the buffer instead of a path.
* This matches what musl is doing.
*/
if (ret == 0 || buf[0] != '/') {
SET_ERRNO(ENOENT);
return NULL;
}
/* ret must be the number of bytes written at this point,
* so return the pointer to buf.
*/
return buf;
}
static __attribute__((unused))
int msleep(unsigned int msecs)
{
@ -86,6 +128,22 @@ int msleep(unsigned int msecs)
return 0;
}
/*
* ssize_t readlink(const char *path, char *buf, size_t bufsiz);
*/
static __attribute__((unused))
ssize_t _sys_readlink(const char *path, char *buf, size_t bufsiz)
{
return __nolibc_syscall4(__NR_readlinkat, AT_FDCWD, path, buf, bufsiz);
}
static __attribute__((unused))
ssize_t readlink(const char *path, char *buf, size_t bufsiz)
{
return __sysret(_sys_readlink(path, buf, bufsiz));
}
static __attribute__((unused))
unsigned int sleep(unsigned int seconds)
{

2
tools/testing/selftests/nolibc/Makefile.include
View File

@ -5,7 +5,7 @@ _CFLAGS_STACKPROTECTOR ?= $(call try-run, \
echo 'void foo(void) {}' | $(CC) -x c - -o - -S $(CLANG_CROSS_FLAGS) $(__CFLAGS_STACKPROTECTOR) | grep -q __stack_chk_guard, \
$(__CFLAGS_STACKPROTECTOR))
_CFLAGS_SANITIZER ?= $(call cc-option,-fsanitize=undefined -fsanitize-trap=all)
CFLAGS_NOLIBC_TEST ?= -Os -fno-ident -fno-asynchronous-unwind-tables -std=c89 \
CFLAGS_NOLIBC_TEST ?= -Os -fno-ident -fno-asynchronous-unwind-tables -std=c89 -ggdb \
-W -Wall -Wextra -Wundef -Wwrite-strings \
$(call cc-option,-fno-stack-protector) $(call cc-option,-Wmissing-prototypes) \
$(_CFLAGS_STACKPROTECTOR) $(_CFLAGS_SANITIZER)

2
tools/testing/selftests/nolibc/Makefile.nolibc
View File

@ -112,6 +112,7 @@ EXTRACONFIG_armthumb = -e CONFIG_NAMESPACES
EXTRACONFIG_sparc32 = -e CONFIG_TMPFS
EXTRACONFIG_m68k = -e CONFIG_BLK_DEV_INITRD
EXTRACONFIG_sh4 = -e CONFIG_BLK_DEV_INITRD -e CONFIG_CMDLINE_FROM_BOOTLOADER
EXTRACONFIG_alpha = -e CONFIG_BLK_DEV_INITRD
EXTRACONFIG = $(EXTRACONFIG_$(XARCH))
# optional tests to run (default = all)
@ -174,6 +175,7 @@ QEMU_ARGS_m68k = -M virt -append "console=ttyGF0,115200 panic=-1 $(TEST:%=
QEMU_ARGS_sh4 = -M r2d -serial file:/dev/stdout -append "console=ttySC1,115200 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
QEMU_ARGS_openrisc = -M virt -m 512M -append "console=ttyS0 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
QEMU_ARGS_parisc32 = -M B160L -append "console=ttyS0 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
QEMU_ARGS_alpha = -M clipper -append "console=ttyS0 panic=-1 $(TEST:%=NOLIBC_TEST=%)"
QEMU_ARGS = -m 1G $(QEMU_ARGS_$(XARCH)) $(QEMU_ARGS_BIOS) $(QEMU_ARGS_EXTRA)
# OUTPUT is only set when run from the main makefile, otherwise

57
tools/testing/selftests/nolibc/nolibc-test.c
View File

@ -756,6 +756,10 @@ int run_startup(int min, int max)
/* checking NULL for argv/argv0, environ and _auxv is not enough, let's compare with sbrk(0) or &end */
extern char end;
char *brk = sbrk(0) != (void *)-1 ? sbrk(0) : &end;
#if defined(__alpha__)
/* the ordering above does not work on an alpha kernel due to STACK_TOP != TASK_SIZE */
brk = NULL;
#endif
/* differ from nolibc, both glibc and musl have no global _auxv */
const unsigned long *test_auxv = (void *)-1;
#ifdef NOLIBC
@ -854,6 +858,58 @@ static int test_dirent(void)
return 0;
}
int test_getcwd(void)
{
char cwd_syscall[PATH_MAX];
char cwd_proc[PATH_MAX];
ssize_t len;
/* Read where the link /proc/self/cwd points */
len = readlink("/proc/self/cwd", cwd_proc, sizeof(cwd_proc) - 1);
if (len <= 0)
return __LINE__;
/* Terminate the string from readlink() */
cwd_proc[len] = '\0';
/* Get the cwd via syscall */
if (getcwd(cwd_syscall, sizeof(cwd_syscall)) == NULL)
return __LINE__;
/* Fail if they aren't the same */
if (strcmp(cwd_proc, cwd_syscall) != 0)
return __LINE__;
/* Try getcwd() with NULL for the buffer,
* should return NULL and an error in errno.
* Other libc's allow this by allocating a buffer
* internally.
*/
if (is_nolibc) {
errno = 0;
if (getcwd(NULL, 0) != NULL || !errno)
return __LINE__;
}
/* Try getcwd() with a buffer but make the size 0,
* should return NULL and an error in errno.
*/
errno = 0;
if (getcwd(cwd_syscall, 0) != NULL || !errno)
return __LINE__;
/* Try getcwd() with a buffer but make the size 1,
* should return NULL and an error in errno because
* the string written to the buffer is terminated
* so you need at least 2 bytes even for "/".
*/
errno = 0;
if (getcwd(cwd_syscall, 1) != NULL || !errno)
return __LINE__;
return 0;
}
int test_getrandom(void)
{
uint64_t rng = 0;
@ -1555,6 +1611,7 @@ int run_syscall(int min, int max)
CASE_TEST(clock_getres); EXPECT_SYSZR(1, clock_getres(CLOCK_MONOTONIC, &ts)); break;
CASE_TEST(clock_gettime); EXPECT_SYSZR(1, clock_gettime(CLOCK_MONOTONIC, &ts)); break;
CASE_TEST(clock_settime); EXPECT_SYSER(1, clock_settime(CLOCK_MONOTONIC, &ts), -1, EINVAL); break;
CASE_TEST(getcwd); EXPECT_SYSZR(proc, test_getcwd()); break;
CASE_TEST(getpid); EXPECT_SYSNE(1, getpid(), -1); break;
CASE_TEST(getppid); EXPECT_SYSNE(1, getppid(), -1); break;
CASE_TEST(gettid); EXPECT_SYSNE(has_gettid, gettid(), -1); break;

3
tools/testing/selftests/nolibc/run-tests.sh
View File

@ -30,6 +30,7 @@ all_archs=(
m68k
sh4
parisc32
alpha
)
archs="${all_archs[@]}"
@ -193,7 +194,7 @@ test_arch() {
exit 1
esac
printf '%-15s' "$arch:"
if [ "$arch" = "m68k" -o "$arch" = "sh4" -o "$arch" = "openrisc" -o "$arch" = "parisc32" ] && [ "$llvm" = "1" ]; then
if [ "$arch" = "m68k" -o "$arch" = "sh4" -o "$arch" = "openrisc" -o "$arch" = "parisc32" -o "$arch" = "alpha" ] && [ "$llvm" = "1" ]; then
echo "Unsupported configuration"
return
fi