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kernel: fix objtool build on macOS hosts

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Since kernel 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.

This fixes:

  CC      …/linux-6.18.33/tools/objtool/builtin-check.o
builtin-check.c:13:10: fatal error: 'sys/sendfile.h' file
      not found
   13 | #include <sys/sendfile.h>
      |          ^~~~~~~~~~~~~~~~
1 error generated.
gmake[8]: *** […/linux-6.18.33/tools/build/Makefile.build:86: …/linux-6.18.33/tools/objtool/builtin-check.o] Error 1

Fixes: https://github.com/openwrt/openwrt/issues/23356
Signed-off-by: Mark Mentovai <mark@mentovai.com>
Link: https://github.com/openwrt/openwrt/pull/23612
Signed-off-by: Robert Marko <robimarko@gmail.com>
This commit is contained in:
Mark Mentovai 2026-06-01 09:16:59 -04:00 committed by Robert Marko
parent e288f421f8
commit b0d2cee3ea
1 changed files with 91 additions and 0 deletions
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91
target/linux/generic/hack-6.18/202-objtool_portability.patch Normal file
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@ -0,0 +1,91 @@
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);