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kbuild: Strip trailing padding bytes from modules.builtin.modinfo

After commit d50f21091358 ("kbuild: align modinfo section for Secureboot
Authenticode EDK2 compat"), running modules_install with certain
versions of kmod (such as 29.1 in Ubuntu Jammy) in certain
configurations may fail with:

depmod: ERROR: kmod_builtin_iter_next: unexpected string without modname prefix

The additional padding bytes to ensure .modinfo is aligned within
vmlinux.unstripped are unexpected by kmod, as this section has always
just been null-terminated strings.

Strip the trailing padding bytes from modules.builtin.modinfo after it
has been extracted from vmlinux.unstripped to restore the format that
kmod expects while keeping .modinfo aligned within vmlinux.unstripped to
avoid regressing the Authenticode calculation fix for EDK2.

Cc: stable@vger.kernel.org
Fixes: d50f21091358 ("kbuild: align modinfo section for Secureboot Authenticode EDK2 compat")
Reported-by: Omar Sandoval <osandov@fb.com>
Reported-by: Samir M <samir@linux.ibm.com>
Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Closes: https://lore.kernel.org/7fef7507-ad64-4e51-9bb8-c9fb6532e51e@linux.ibm.com/
Tested-by: Omar Sandoval <osandov@fb.com>
Tested-by: Samir M <samir@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Link: https://patch.msgid.link/20251105-kbuild-fix-builtin-modinfo-for-kmod-v1-1-b419d8ad4606@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Nathan Chancellor a26a6c93 6146a0f1

+14 -1
+14 -1
scripts/Makefile.vmlinux
··· 102 102 # modules.builtin.modinfo 103 103 # --------------------------------------------------------------------------- 104 104 105 + # .modinfo in vmlinux.unstripped is aligned to 8 bytes for compatibility with 106 + # tools that expect vmlinux to have sufficiently aligned sections but the 107 + # additional bytes used for padding .modinfo to satisfy this requirement break 108 + # certain versions of kmod with 109 + # 110 + # depmod: ERROR: kmod_builtin_iter_next: unexpected string without modname prefix 111 + # 112 + # Strip the trailing padding bytes after extracting .modinfo to comply with 113 + # what kmod expects to parse. 114 + quiet_cmd_modules_builtin_modinfo = GEN $@ 115 + cmd_modules_builtin_modinfo = $(cmd_objcopy); \ 116 + sed -i 's/\x00\+$$/\x00/g' $@ 117 + 105 118 OBJCOPYFLAGS_modules.builtin.modinfo := -j .modinfo -O binary 106 119 107 120 targets += modules.builtin.modinfo 108 121 modules.builtin.modinfo: vmlinux.unstripped FORCE 109 - $(call if_changed,objcopy) 122 + $(call if_changed,modules_builtin_modinfo) 110 123 111 124 # modules.builtin 112 125 # ---------------------------------------------------------------------------