tools/nolibc: add mremap()

This is used in various selftests and will be handy when integrating
those with nolibc.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250428-nolibc-misc-v2-4-3c043eeab06c@linutronix.de
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

2 files changed, 30 insertions, 3 deletions

diff --git a/tools/include/nolibc/sys/mman.h b/tools/include/nolibc/sys/mman.h
index 41c7bf45e427..5228751b458c 100644
--- a/tools/include/nolibc/sys/mman.h
+++ b/tools/include/nolibc/sys/mman.h
@@ -49,6 +49,25 @@ void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
 }
 
 static __attribute__((unused))
+void *sys_mremap(void *old_address, size_t old_size, size_t new_size, int flags, void *new_address)
+{
+	return (void *)my_syscall5(__NR_mremap, old_address, old_size,
+				   new_size, flags, new_address);
+}
+
+static __attribute__((unused))
+void *mremap(void *old_address, size_t old_size, size_t new_size, int flags, void *new_address)
+{
+	void *ret = sys_mremap(old_address, old_size, new_size, flags, new_address);
+
+	if ((unsigned long)ret >= -4095UL) {
+		SET_ERRNO(-(long)ret);
+		ret = MAP_FAILED;
+	}
+	return ret;
+}
+
+static __attribute__((unused))
 int sys_munmap(void *addr, size_t length)
 {
 	return my_syscall2(__NR_munmap, addr, length);
diff --git a/tools/testing/selftests/nolibc/nolibc-test.c b/tools/testing/selftests/nolibc/nolibc-test.c
index b7440a667db6..abe0ae794208 100644
--- a/tools/testing/selftests/nolibc/nolibc-test.c
+++ b/tools/testing/selftests/nolibc/nolibc-test.c
@@ -926,7 +926,7 @@ int test_mmap_munmap(void)
 {
 	int ret, fd, i, page_size;
 	void *mem;
-	size_t file_size, length;
+	size_t file_size, length, mem_length;
 	off_t offset, pa_offset;
 	struct stat stat_buf;
 	const char * const files[] = {
@@ -966,14 +966,22 @@ int test_mmap_munmap(void)
 		offset = 0;
 	length = file_size - offset;
 	pa_offset = offset & ~(page_size - 1);
+	mem_length = length + offset - pa_offset;
 
-	mem = mmap(NULL, length + offset - pa_offset, PROT_READ, MAP_SHARED, fd, pa_offset);
+	mem = mmap(NULL, mem_length, PROT_READ, MAP_SHARED, fd, pa_offset);
 	if (mem == MAP_FAILED) {
 		ret = 1;
 		goto end;
 	}
 
-	ret = munmap(mem, length + offset - pa_offset);
+	mem = mremap(mem, mem_length, mem_length * 2, MREMAP_MAYMOVE, 0);
+	if (mem == MAP_FAILED) {
+		munmap(mem, mem_length);
+		ret = 1;
+		goto end;
+	}
+
+	ret = munmap(mem, mem_length * 2);
 
 end:
 	close(fd);