From dc5565c4478135999d8bb193bd9dfb4f8ef5f96b Mon Sep 17 00:00:00 2001
From: Mark Mentovai <mark@mentovai.com>
Date: Mon, 1 Jun 2026 09:11:43 -0400
Subject: [PATCH] objtool: fix build on macOS hosts

Since 5a406031d0719 (2025-03-17, in 6.15), objtool calls sendfile, but
sendfile is Linux-specific and a sendfile with the requisite
capabilities is not available on other operating systems. Provide a more
portable fallback implementation to be used when cross-building on
non-Linux hosts.

Signed-off-by: Mark Mentovai <mark@mentovai.com>
---
 tools/objtool/builtin-check.c | 40 +++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -10,7 +10,9 @@
 #include <unistd.h>
 #include <errno.h>
 #include <sys/stat.h>
+#ifdef __linux__
 #include <sys/sendfile.h>
+#endif
 #include <objtool/builtin.h>
 #include <objtool/objtool.h>
 #include <objtool/warn.h>
@@ -187,12 +189,28 @@ static bool opts_valid(void)
 	return false;
 }
 
+#ifndef __linux__
+#define RETRY_EINTR(x)                                                  \
+	({                                                              \
+		__typeof__(x) eintr_wrapper_result;                     \
+		do {                                                    \
+			eintr_wrapper_result = (x);                     \
+		} while (eintr_wrapper_result == -1 && errno == EINTR); \
+		eintr_wrapper_result;                                   \
+	})
+#endif
+
 static int copy_file(const char *src, const char *dst)
 {
 	size_t to_copy, copied;
 	int dst_fd, src_fd;
 	struct stat stat;
+#ifdef __linux__
 	off_t offset = 0;
+#else
+	char buf[65536];
+	ssize_t nread, nwrote;
+#endif
 
 	src_fd = open(src, O_RDONLY);
 	if (src_fd == -1) {
@@ -217,11 +235,33 @@ static int copy_file(const char *src, co
 	}
 
 	for (to_copy = stat.st_size; to_copy > 0; to_copy -= copied) {
+#ifdef __linux__
 		copied = sendfile(dst_fd, src_fd, &offset, to_copy);
 		if (copied == -1) {
 			ERROR_GLIBC("sendfile");
 			return 1;
 		}
+#else
+		nread = RETRY_EINTR(
+			read(src_fd, buf,
+			     to_copy < sizeof(buf) ? to_copy : sizeof(buf)));
+		if (nread < 0) {
+			ERROR_GLIBC("read");
+			return 1;
+		}
+		if (nread == 0) {
+			ERROR("unexpected premature EOF");
+			return 1;
+		}
+		for (copied = 0; copied < nread; copied += nwrote) {
+			nwrote = RETRY_EINTR(
+				write(dst_fd, buf + copied, nread - copied));
+			if (nwrote < 0) {
+				ERROR_GLIBC("write");
+				return 1;
+			}
+		}
+#endif
 	}
 
 	close(dst_fd);