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()

12 files changed, 284 insertions, 11 deletions

diff --git a/tools/include/nolibc/Makefile b/tools/include/nolibc/Makefile
index 00fd2e566d75..6d213d372bf8 100644
--- a/tools/include/nolibc/Makefile
+++ b/tools/include/nolibc/Makefile
@@ -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 \
diff --git a/tools/include/nolibc/arch-alpha.h b/tools/include/nolibc/arch-alpha.h
new file mode 100644
index 000000000000..04ff8a95c52c
--- /dev/null
+++ b/tools/include/nolibc/arch-alpha.h
@@ -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 */
diff --git a/tools/include/nolibc/arch-arm.h b/tools/include/nolibc/arch-arm.h
index 8681922e05ca..b88686fb19c4 100644
--- a/tools/include/nolibc/arch-arm.h
+++ b/tools/include/nolibc/arch-arm.h
@@ -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)
diff --git a/tools/include/nolibc/arch-powerpc.h b/tools/include/nolibc/arch-powerpc.h
index a1ab91d55384..dbe2e5205aaa 100644
--- a/tools/include/nolibc/arch-powerpc.h
+++ b/tools/include/nolibc/arch-powerpc.h
@@ -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)                                               \
 ({                                                                           \
diff --git a/tools/include/nolibc/arch-sparc.h b/tools/include/nolibc/arch-sparc.h
index ddae9bc10dfe..23fab40accfa 100644
--- a/tools/include/nolibc/arch-sparc.h
+++ b/tools/include/nolibc/arch-sparc.h
@@ -45,7 +45,7 @@
 									      \
 	__asm__ volatile (                                                    \
 		_NOLIBC_SYSCALL                                               \
-		: "+r"(_arg1)                                                 \
+		: "=r"(_arg1)                                                 \
 		: "r"(_num)                                                   \
 		: "memory", "cc"                                              \
 	);                                                                    \
diff --git a/tools/include/nolibc/arch-x86.h b/tools/include/nolibc/arch-x86.h
index fe152ac2650b..577e9b682eb3 100644
--- a/tools/include/nolibc/arch-x86.h
+++ b/tools/include/nolibc/arch-x86.h
@@ -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)                                                \
 ({                                                                            \
diff --git a/tools/include/nolibc/arch.h b/tools/include/nolibc/arch.h
index b69d9c5ec5c6..06cc2dbe7a33 100644
--- a/tools/include/nolibc/arch.h
+++ b/tools/include/nolibc/arch.h
@@ -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
diff --git a/tools/include/nolibc/unistd.h b/tools/include/nolibc/unistd.h
index 79599ceef45d..a264a20da13d 100644
--- a/tools/include/nolibc/unistd.h
+++ b/tools/include/nolibc/unistd.h
@@ -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)
 {
diff --git a/tools/testing/selftests/nolibc/Makefile.include b/tools/testing/selftests/nolibc/Makefile.include
index c30ca3a9ef14..ea520eac64a6 100644
--- a/tools/testing/selftests/nolibc/Makefile.include
+++ b/tools/testing/selftests/nolibc/Makefile.include
@@ -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)
diff --git a/tools/testing/selftests/nolibc/Makefile.nolibc b/tools/testing/selftests/nolibc/Makefile.nolibc
index 06f881e2e90c..f70c8dfca018 100644
--- a/tools/testing/selftests/nolibc/Makefile.nolibc
+++ b/tools/testing/selftests/nolibc/Makefile.nolibc
@@ -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
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index c1c1ce43a047..ed860b0a15a1 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -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;
diff --git a/tools/testing/selftests/nolibc/run-tests.sh b/tools/testing/selftests/nolibc/run-tests.sh
index 6460e25001de..dc0b1649c641 100755
--- a/tools/testing/selftests/nolibc/run-tests.sh
+++ b/tools/testing/selftests/nolibc/run-tests.sh
@@ -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