Merge tag 'kbuild-6.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux

Pull Kbuild updates from Nathan Chancellor:

 - Extend modules.builtin.modinfo to include module aliases from
   MODULE_DEVICE_TABLE for builtin modules so that userspace tools (such
   as kmod) can verify that a particular module alias will be handled by
   a builtin module

 - Bump the minimum version of LLVM for building the kernel to 15.0.0

 - Upgrade several userspace API checks in headers_check.pl to errors

 - Unify and consolidate CONFIG_WERROR / W=e handling

 - Turn assembler and linker warnings into errors with CONFIG_WERROR /
   W=e

 - Respect CONFIG_WERROR / W=e when building userspace programs
   (userprogs)

 - Enable -Werror unconditionally when building host programs
   (hostprogs)

 - Support copy_file_range() and data segment alignment in gen_init_cpio
   to improve performance on filesystems that support reflinks such as
   btrfs and XFS

 - Miscellaneous small changes to scripts and configuration files

* tag 'kbuild-6.18-1' of git://git.kernel.org/pub/scm/linux/kernel/git/kbuild/linux: (47 commits)
  modpost: Initialize builtin_modname to stop SIGSEGVs
  Documentation: kbuild: note CONFIG_DEBUG_EFI in reproducible builds
  kbuild: vmlinux.unstripped should always depend on .vmlinux.export.o
  modpost: Create modalias for builtin modules
  modpost: Add modname to mod_device_table alias
  scsi: Always define blogic_pci_tbl structure
  kbuild: extract modules.builtin.modinfo from vmlinux.unstripped
  kbuild: keep .modinfo section in vmlinux.unstripped
  kbuild: always create intermediate vmlinux.unstripped
  s390: vmlinux.lds.S: Reorder sections
  KMSAN: Remove tautological checks
  objtool: Drop noinstr hack for KCSAN_WEAK_MEMORY
  lib/Kconfig.debug: Drop CLANG_VERSION check from DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
  riscv: Remove ld.lld version checks from many TOOLCHAIN_HAS configs
  riscv: Unconditionally use linker relaxation
  riscv: Remove version check for LTO_CLANG selects
  powerpc: Drop unnecessary initializations in __copy_inst_from_kernel_nofault()
  mips: Unconditionally select ARCH_HAS_CURRENT_STACK_POINTER
  arm64: Remove tautological LLVM Kconfig conditions
  ARM: Clean up definition of ARM_HAS_GROUP_RELOCS
  ...

init/initramfs_test.c

@@ -45,8 +45,11 @@ static size_t fill_cpio(struct initramfs_test_cpio *cs, size_t csz, char *out)
 			c->mtime, c->filesize, c->devmajor, c->devminor,
 			c->rdevmajor, c->rdevminor, c->namesize, c->csum,
 			c->fname) + 1;
+
 		pr_debug("packing (%zu): %.*s\n", thislen, (int)thislen, pos);
-		off += thislen;
+		if (thislen != CPIO_HDRLEN + c->namesize)
+			pr_debug("padded to: %u\n", CPIO_HDRLEN + c->namesize);
+		off += CPIO_HDRLEN + c->namesize;
 		while (off & 3)
 			out[off++] = '\0';
 
@@ -383,6 +386,67 @@ static void __init initramfs_test_many(struct kunit *test)
 	kfree(cpio_srcbuf);
 }
 
+/*
+ * An initramfs filename is namesize in length, including the zero-terminator.
+ * A filename can be zero-terminated prior to namesize, with the remainder used
+ * as padding. This can be useful for e.g. alignment of file data segments with
+ * a 4KB filesystem block, allowing for extent sharing (reflinks) between cpio
+ * source and destination. This hack works with both GNU cpio and initramfs, as
+ * long as PATH_MAX isn't exceeded.
+ */
+static void __init initramfs_test_fname_pad(struct kunit *test)
+{
+	char *err;
+	size_t len;
+	struct file *file;
+	char fdata[] = "this file data is aligned at 4K in the archive";
+	struct test_fname_pad {
+		char padded_fname[4096 - CPIO_HDRLEN];
+		char cpio_srcbuf[CPIO_HDRLEN + PATH_MAX + 3 + sizeof(fdata)];
+	} *tbufs = kzalloc(sizeof(struct test_fname_pad), GFP_KERNEL);
+	struct initramfs_test_cpio c[] = { {
+		.magic = "070701",
+		.ino = 1,
+		.mode = S_IFREG | 0777,
+		.uid = 0,
+		.gid = 0,
+		.nlink = 1,
+		.mtime = 1,
+		.filesize = sizeof(fdata),
+		.devmajor = 0,
+		.devminor = 1,
+		.rdevmajor = 0,
+		.rdevminor = 0,
+		/* align file data at 4K archive offset via padded fname */
+		.namesize = 4096 - CPIO_HDRLEN,
+		.csum = 0,
+		.fname = tbufs->padded_fname,
+		.data = fdata,
+	} };
+
+	memcpy(tbufs->padded_fname, "padded_fname", sizeof("padded_fname"));
+	len = fill_cpio(c, ARRAY_SIZE(c), tbufs->cpio_srcbuf);
+
+	err = unpack_to_rootfs(tbufs->cpio_srcbuf, len);
+	KUNIT_EXPECT_NULL(test, err);
+
+	file = filp_open(c[0].fname, O_RDONLY, 0);
+	if (IS_ERR(file)) {
+		KUNIT_FAIL(test, "open failed");
+		goto out;
+	}
+
+	/* read back file contents into @cpio_srcbuf and confirm match */
+	len = kernel_read(file, tbufs->cpio_srcbuf, c[0].filesize, NULL);
+	KUNIT_EXPECT_EQ(test, len, c[0].filesize);
+	KUNIT_EXPECT_MEMEQ(test, tbufs->cpio_srcbuf, c[0].data, len);
+
+	fput(file);
+	KUNIT_EXPECT_EQ(test, init_unlink(c[0].fname), 0);
+out:
+	kfree(tbufs);
+}
+
 /*
  * The kunit_case/_suite struct cannot be marked as __initdata as this will be
  * used in debugfs to retrieve results after test has run.
@@ -394,6 +458,7 @@ static struct kunit_case __refdata initramfs_test_cases[] = {
 	KUNIT_CASE(initramfs_test_csum),
 	KUNIT_CASE(initramfs_test_hardlink),
 	KUNIT_CASE(initramfs_test_many),
+	KUNIT_CASE(initramfs_test_fname_pad),
 	{},
 };