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15fa203ef9
find_sympos() calculates a sympos used by livepatch to disambiguate
duplicately-named symbols. For function symbols, there's a hack which
counts .text.unlikely symbols before other .text symbols, matching the
linker script's section ordering.
Not only is the hack fragile, data symbols can have the same problem.
So for example, adding a reference to pwq_cache in
ep_unregister_pollwait() can trigger a corrupt sympos and a relocation
to the wrong pwq_cache symbol in the livepatch module, resulting in a
crash or undefined behavior.
Remove the existing hack in favor of a fully deterministic solution,
using the new .klp.symid table to derive the symbol-to-id mapping from
the original vmlinux.o and the id-to-address mapping from the
corresponding vmlinux, which can then be used to determine the exact
sympos associated with the original vmlinux.
Modules don't need any special treatment: the .ko has the same
section/symbol ordering as the original whole-archive symbol table.
Fixes: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Reported-by: Ben Procknow <bprockno@redhat.com>
Reported-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: live-patching@vger.kernel.org
Link: https://lore.kernel.org/20260710153042.3156788-1-joe.lawrence@redhat.com
Link: https://lore.kernel.org/20260724221730.3126529-1-joe.lawrence@redhat.com
Link: https://patch.msgid.link/919785e3bf2245db02ff6391e735d9cb139170b1.1785727106.git.jpoimboe@kernel.org
59 lines
1.6 KiB
C
59 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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#ifndef _OBJTOOL_KLP_H
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#define _OBJTOOL_KLP_H
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#define SHF_RELA_LIVEPATCH 0x00100000
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#define SHN_LIVEPATCH 0xff20
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/*
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* .init.klp_objects and .init.klp_funcs are created by klp diff and used by the
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* patch module init code to build the klp_patch, klp_object and klp_func
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* structs needed by the livepatch API.
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*/
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#define KLP_OBJECTS_SEC ".init.klp_objects"
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#define KLP_FUNCS_SEC ".init.klp_funcs"
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/*
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* __klp_relocs is an intermediate section which are created by klp diff and
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* converted into KLP symbols/relas by "objtool klp post-link". This is needed
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* to work around the linker, which doesn't preserve SHN_LIVEPATCH or
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* SHF_RELA_LIVEPATCH, nor does it support having two RELA sections for a
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* single PROGBITS section.
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*/
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#define KLP_RELOCS_SEC "__klp_relocs"
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#define KLP_STRINGS_SEC ".rodata.klp.str1.1"
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#define KLP_TOMBSTONE_PREFIX ".klp.tombstone."
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struct klp_reloc {
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void *offset;
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void *sym;
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u32 type;
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};
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/*
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* .klp.symid is used to correlate symbols between vmlinux.o and vmlinux, for
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* calculating sympos to disambiguate duplicately-named symbols.
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*/
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#define KLP_SYMID_SEC ".klp.symid"
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struct klp_symid {
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u64 id;
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u64 addr;
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};
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struct objtool_file;
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struct elf;
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struct symbol;
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int klp_create_symid_sections(struct objtool_file *file);
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int klp_sympos_init(struct elf *orig);
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unsigned long klp_find_sympos(struct elf *elf, struct symbol *sym);
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int cmd_klp_checksum(int argc, const char **argv);
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int cmd_klp_diff(int argc, const char **argv);
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int cmd_klp_post_link(int argc, const char **argv);
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#endif /* _OBJTOOL_KLP_H */
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