tools/nolibc: add support for pread() and pwrite()

These are standard function to interact with a file descriptor without
touching its internal file offset.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Willy Tarreau <w@1wt.eu>
Link: https://patch.msgid.link/20260927-nolibc-pread-v1-5-e9af6e47b37a@weissschuh.net

2 files changed, 68 insertions, 0 deletions

diff --git a/tools/include/nolibc/arch-sh.h b/tools/include/nolibc/arch-sh.h
index a32378fd621f..996cfbe1bee3 100644
--- a/tools/include/nolibc/arch-sh.h
+++ b/tools/include/nolibc/arch-sh.h
@@ -10,6 +10,8 @@
 #include "compiler.h"
 #include "crt.h"
 
+#include <linux/unistd.h>
+
 /*
  * Syscalls for SuperH:
  *   - registers are 32bit wide
@@ -161,4 +163,20 @@ void __attribute__((weak, noreturn)) __nolibc_entrypoint __nolibc_no_stack_prote
 }
 #endif /* NOLIBC_NO_RUNTIME */
 
+static __attribute__((unused))
+ssize_t _sys_pread(int fd, void *buf, size_t count, off_t offset)
+{
+	return __nolibc_syscall6(__NR_pread64, fd, buf, count, 0,
+				 __NOLIBC_LLARGPART(offset, 0), __NOLIBC_LLARGPART(offset, 1));
+}
+#define _sys_pread _sys_pread
+
+static __attribute__((unused))
+ssize_t _sys_pwrite(int fd, const void *buf, size_t count, off_t offset)
+{
+	return __nolibc_syscall6(__NR_pwrite64, fd, buf, count, 0,
+				 __NOLIBC_LLARGPART(offset, 0), __NOLIBC_LLARGPART(offset, 1));
+}
+#define _sys_pwrite _sys_pwrite
+
 #endif /* _NOLIBC_ARCH_SH_H */
diff --git a/tools/include/nolibc/sys.h b/tools/include/nolibc/sys.h
index 7f06d27da612..b63fa6c618c5 100644
--- a/tools/include/nolibc/sys.h
+++ b/tools/include/nolibc/sys.h
@@ -746,6 +746,56 @@ int pivot_root(const char *new, const char *old)
 
 
 /*
+ * ssize_t pread(int fd, void *buf, size_t count, off_t offset);
+ * ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset);
+ */
+
+#ifndef _sys_pread
+static __attribute__((unused))
+ssize_t _sys_pread(int fd, void *buf, size_t count, off_t offset)
+{
+#if __NOLIBC_BITS_PER_SYSCALL_ARG == 64
+	return __nolibc_syscall4(__NR_pread64, fd, buf, count, offset);
+#elif defined(__NOLIBC_PAD_64BIT_SYSCALL_ARGUMENT_PAIR)
+	return __nolibc_syscall6(__NR_pread64, fd, buf, count, 0,
+				 __NOLIBC_LLARGPART(offset, 0), __NOLIBC_LLARGPART(offset, 1));
+#else
+	return __nolibc_syscall5(__NR_pread64, fd, buf, count,
+				 __NOLIBC_LLARGPART(offset, 0), __NOLIBC_LLARGPART(offset, 1));
+#endif
+}
+#endif /* _sys_pread */
+
+static __attribute__((unused))
+ssize_t pread(int fd, void *buf, size_t count, off_t offset)
+{
+	return __sysret(_sys_pread(fd, buf, count, offset));
+}
+
+#ifndef _sys_pwrite
+static __attribute__((unused))
+ssize_t _sys_pwrite(int fd, const void *buf, size_t count, off_t offset)
+{
+#if __NOLIBC_BITS_PER_SYSCALL_ARG == 64
+	return __nolibc_syscall4(__NR_pwrite64, fd, buf, count, offset);
+#elif defined(__NOLIBC_PAD_64BIT_SYSCALL_ARGUMENT_PAIR)
+	return __nolibc_syscall6(__NR_pwrite64, fd, buf, count, 0,
+				 __NOLIBC_LLARGPART(offset, 0), __NOLIBC_LLARGPART(offset, 1));
+#else
+	return __nolibc_syscall5(__NR_pwrite64, fd, buf, count,
+				 __NOLIBC_LLARGPART(offset, 0), __NOLIBC_LLARGPART(offset, 1));
+#endif
+}
+#endif /* _sys_pwrite */
+
+static __attribute__((unused))
+ssize_t pwrite(int fd, const void *buf, size_t count, off_t offset)
+{
+	return __sysret(_sys_pwrite(fd, buf, count, offset));
+}
+
+
+/*
  * ssize_t read(int fd, void *buf, size_t count);
  */