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sd-boot: pad .sbat section to 1k bytes

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Fedora's kernels now ship with a .sbat section:
  kernel,1,Red Hat,kernel-core,6.17.0-0.rc1.250814g0cc53520e68b.20.fc44.x86_64,mailto:secalert@redhat.com
  kernel.fedora,1,Red Hat,kernel-core,6.17.0-0.rc1.250814g0cc53520e68b.20.fc44.x86_64,mailto:secalert@redhat.com
This pushes the combined .sbat section just over its pre-allocated size of 512 bytes:
  File "/usr/bin/ukify", line 1048, in pe_add_sections
    raise PEError(f'Not enough space in existing section {section.name} to append new data')
  PEError: Not enough space in existing section .sbat to append new data

PE sections need to align to 512 bytes, so to make it all fit we pad the .sbat
section with zeros to 1k. Various tools already should strip trailing zeros when
using sbat sections, since ukify always inserts a trailing NUL.

The defines are moved to sbat.h, they are used only in sd-stub and sd-boot.
This commit is contained in:
Zbigniew Jędrzejewski-Szmek
2025-08-19 11:50:27 +02:00
parent ec1d031f3d
commit b4a1854397
3 changed files with 23 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/boot/stub.c
+1 -1
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@@ -51,7 +51,7 @@ enum {
/* magic string to find in the binary image */
DECLARE_NOALLOC_SECTION(".sdmagic", "#### LoaderInfo: systemd-stub " GIT_VERSION " ####");
DECLARE_SBAT(SBAT_STUB_SECTION_TEXT);
DECLARE_SBAT_PADDED(SBAT_STUB_SECTION_TEXT);
static char16_t* pe_section_to_str16(
EFI_LOADED_IMAGE_PROTOCOL *loaded_image,
src/fundamental/macro-fundamental.h
+14 -9
View File
@@ -436,17 +436,22 @@ assert_cc(sizeof(dummy_t) == 0);
}
#endif
/* Declares an ELF read-only string section that does not occupy memory at runtime. */
#define DECLARE_NOALLOC_SECTION(name, text) \
asm(".pushsection " name ",\"S\"\n\t" \
".ascii " STRINGIFY(text) "\n\t" \
/* Declare an ELF read-only string section that does not occupy memory at runtime. */
#define DECLARE_NOALLOC_SECTION(name, text) \
asm(".pushsection " name ",\"S\"\n\t" \
".ascii " STRINGIFY(text) "\n\t" \
".popsection\n")
#ifdef SBAT_DISTRO
# define DECLARE_SBAT(text) DECLARE_NOALLOC_SECTION(".sbat", text)
#else
# define DECLARE_SBAT(text)
#endif
/* Similar to DECLARE_NOALLOC_SECTION, but pad the section with extra 512 bytes. After taking alignment into
* account, the section has up to 1024 bytes minus the size of the original content of padding, and this
* extra space can be used to extend the contents. This is intended for the .sbat section. */
#define DECLARE_NOALLOC_SECTION_PADDED(name, text) \
assert_cc(STRLEN(text) <= 512); \
asm(".pushsection " name ",\"S\"\n\t" \
".ascii " STRINGIFY(text) "\n\t" \
".balign 512\n\t" \
".fill 512, 1, 0\n\t" \
".popsection\n")
#define typeof_field(struct_type, member) typeof(((struct_type *) 0)->member)
#define sizeof_field(struct_type, member) sizeof(((struct_type *) 0)->member)
src/fundamental/sbat.h
+8
View File
@@ -12,3 +12,11 @@
SBAT_PROJECT "-stub" ",1,The systemd Developers," SBAT_PROJECT "," PROJECT_VERSION "," PROJECT_URL "\n" \
SBAT_PROJECT "-stub" "." SBAT_DISTRO "," STRINGIFY(SBAT_DISTRO_GENERATION) "," SBAT_DISTRO_SUMMARY "," SBAT_DISTRO_PKGNAME "," SBAT_DISTRO_VERSION "," SBAT_DISTRO_URL "\n"
#endif
#ifdef SBAT_DISTRO
# define DECLARE_SBAT(text) DECLARE_NOALLOC_SECTION(".sbat", text)
# define DECLARE_SBAT_PADDED(text) DECLARE_NOALLOC_SECTION_PADDED(".sbat", text)
#else
# define DECLARE_SBAT(text)
# define DECLARE_SBAT_PADDED(text)
#endif