mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-09-10 17:00:41 -04:00
3a83d9cd3d
Testing klp-build with arm64 produced the following linker error during
the original kernel build:
`__notrim.1' referenced in section `.klp.symid' of vmlinux.o: defined in discarded section `.no_trim_symbol' of vmlinux.o
symbol_get() puts a static __notrim[] in .no_trim_symbol, which GCC
names __notrim.1, __notrim.2, etc. Two or more built-in translation
units calling symbol_get() thus produce duplicate names, resulting in
corresponding .klp.symid references which trigger the above error.
Add .no_trim_symbol to the discarded section list so its symbols don't
get symids.
Note this issue is not specific to arm64: it just needs two built-in
symbol_get() callers. arm64 trips over it easily because it has KVM
always compiled in vmlinux, whereas on x86 it's typically a module.
Fixes: 029223d301 ("objtool/klp: Add .klp.symid for sympos disambiguation")
Acked-by: Song Liu <song@kernel.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Link: https://patch.msgid.link/5a3cc4cded743167dd0878220201d80f7e48e5d7.1786138493.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
119 lines
2.8 KiB
C
119 lines
2.8 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
|
|
/*
|
|
* Emit the .klp.symid table which allows "objtool klp diff" to reliably
|
|
* disambiguate duplicate-named local symbols in vmlinux.
|
|
*
|
|
* Livepatch identifies a duplicate-named symbol by its position (sympos)
|
|
* among the same-named kallsyms entries, counted in ascending address order
|
|
* in the final linked vmlinux. That order can't be derived from vmlinux.o
|
|
* alone: the final link reorders sub-sections (.text.unlikely*, .data..*,
|
|
* etc).
|
|
*
|
|
* Bridge the gap with a table which survives the final link: a single
|
|
* non-alloc section containing an array of { id, addr } entries, where
|
|
* 'id' is a unique counter identifier and 'addr' has a relocation to the
|
|
* symbol. The linker copies 'id' verbatim and resolves 'addr' to the symbol's
|
|
* final address.
|
|
*
|
|
* The table is only emitted for vmlinux.o, and only when klp-build asks for it
|
|
* with KLP_SYMIDS=1, which adds --klp-symids to the vmlinux.o objtool run.
|
|
*
|
|
* It can't survive --gc-sections, which sweeps the whole section; klp-build
|
|
* rejects CONFIG_LD_DEAD_CODE_DATA_ELIMINATION.
|
|
*/
|
|
#include <linux/string.h>
|
|
|
|
#include <objtool/objtool.h>
|
|
#include <objtool/warn.h>
|
|
#include <objtool/endianness.h>
|
|
#include <objtool/klp.h>
|
|
|
|
static const char * const discarded_secs[] = {
|
|
".discard",
|
|
".modinfo",
|
|
".no_trim_symbol",
|
|
"__tracepoint_check",
|
|
};
|
|
|
|
static bool discarded_sec(struct section *sec)
|
|
{
|
|
if (!(sec->sh.sh_flags & SHF_ALLOC))
|
|
return true;
|
|
|
|
for (int i = 0; i < ARRAY_SIZE(discarded_secs); i++)
|
|
if (strstarts(sec->name, discarded_secs[i]))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
static bool symid_needed(struct elf *elf, struct symbol *sym)
|
|
{
|
|
struct symbol *s;
|
|
|
|
if (!is_local_sym(sym) || is_undef_sym(sym))
|
|
return false;
|
|
|
|
if (!is_func_sym(sym) && !is_object_sym(sym))
|
|
return false;
|
|
|
|
if (is_prefix_func(sym))
|
|
return false;
|
|
|
|
if (discarded_sec(sym->sec))
|
|
return false;
|
|
|
|
for_each_sym_by_name(elf, sym->name, s) {
|
|
if (s == sym || is_sec_sym(s) || is_file_sym(s) || is_undef_sym(s))
|
|
continue;
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
int klp_create_symid_sections(struct objtool_file *file)
|
|
{
|
|
struct elf *elf = file->elf;
|
|
struct klp_symid *symids;
|
|
struct section *sec;
|
|
struct symbol *sym;
|
|
u64 nr = 0, i = 0;
|
|
|
|
if (!str_ends_with(objname, "vmlinux.o"))
|
|
return 0;
|
|
|
|
for_each_sym(elf, sym)
|
|
if (symid_needed(elf, sym))
|
|
nr++;
|
|
|
|
if (!nr)
|
|
return 0;
|
|
|
|
sec = elf_create_section(elf, KLP_SYMID_SEC, 0, sizeof(struct klp_symid),
|
|
SHT_PROGBITS, 8, 0);
|
|
if (!sec)
|
|
return -1;
|
|
|
|
symids = elf_add_data(elf, sec, NULL, nr * sizeof(struct klp_symid));
|
|
if (!symids)
|
|
return -1;
|
|
|
|
for_each_sym(elf, sym) {
|
|
if (!symid_needed(elf, sym))
|
|
continue;
|
|
|
|
symids[i].id = bswap_if_needed(elf, i);
|
|
|
|
if (!elf_create_reloc(elf, sec,
|
|
i * sizeof(struct klp_symid) +
|
|
offsetof(struct klp_symid, addr),
|
|
sym, 0, R_ABS64))
|
|
return -1;
|
|
|
|
i++;
|
|
}
|
|
|
|
return 0;
|
|
}
|