From f5f762fc93d0b81d30b815a2f96320909ad10eb3 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Sun, 2 Aug 2026 20:24:26 -0700 Subject: objtool/klp: Skip hidden directories when finding objects klp-build's find_objects() scans the whole tree for vmlinux.o and .ko files, pruning only klp-tmp/ and .git/. Development tools can leave other dot-directories in the tree. Kernel objects never live under hidden directories, so prune them all. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: live-patching@vger.kernel.org Link: https://patch.msgid.link/6c8eaa9feb17e3811f4ef7733fd7288b7f489183.1785727106.git.jpoimboe@kernel.org --- scripts/livepatch/klp-build | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'scripts') diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build index c4a7acf8edc3..a8c103ce7763 100755 --- a/scripts/livepatch/klp-build +++ b/scripts/livepatch/klp-build @@ -575,8 +575,9 @@ find_objects() { local opts=("$@") # Find root-level vmlinux.o and non-root-level .ko files, - # excluding klp-tmp/ and .git/ - find "$PWD" \( -path "$TMP_DIR" -o -path "$PWD/.git" -o -regex "$PWD/[^/][^/]*\.ko" \) -prune -o \ + # excluding klp-tmp/ and hidden directories. + find "$PWD" -mindepth 1 \ + \( -path "$TMP_DIR" -o -name ".*" -o -regex "$PWD/[^/][^/]*\.ko" \) -prune -o \ -type f "${opts[@]}" \ \( -name "*.ko" -o -path "$PWD/vmlinux.o" \) \ -printf '%P\n' -- cgit From 029223d301620bc4e1086696047b0d5d6eba5edd Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Sun, 2 Aug 2026 20:24:27 -0700 Subject: objtool/klp: Add .klp.symid for sympos disambiguation Livepatch identifies a duplicate-named symbol by its position (sympos) among same-named kallsyms entries, which for vmlinux are counted in ascending address order in the final linked kernel. That order can't be reliably derived from vmlinux.o: the final link reorders sub-sections (.text.unlikely*, .data..*, etc). Bridge the gap with a new .klp.symid section which can be used to correlate symbols between vmlinux.o and vmlinux so that klp-diff can reliably determine the sympos. The table can't survive --gc-sections: keeping it alive would keep every duplicate-named symbol's section alive, so the reference kernel would stop matching the one which ships. klp-build rejects CONFIG_LD_DEAD_CODE_DATA_ELIMINATION instead. Nothing is lost today: x86_64 is the only HAVE_KLP_BUILD arch and doesn't select HAVE_LD_DEAD_CODE_DATA_ELIMINATION, arm64 and s390 have never selected it either, and on powerpc, it's still EXPERIMENTAL and disabled by every distro kernel. This is the build-time half of reliable vmlinux sympos computation; "objtool klp diff" will consume the table in a subsequent commit. Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Cc: live-patching@vger.kernel.org Link: https://patch.msgid.link/64d50f077b569f47883c015cdb7079edb068efe8.1785727106.git.jpoimboe@kernel.org --- include/asm-generic/vmlinux.lds.h | 10 ++- scripts/Makefile.vmlinux_o | 3 + scripts/livepatch/klp-build | 5 ++ scripts/mod/modpost.c | 1 + tools/objtool/Build | 1 + tools/objtool/builtin-check.c | 7 ++ tools/objtool/check.c | 7 ++ tools/objtool/include/objtool/builtin.h | 1 + tools/objtool/include/objtool/klp.h | 15 ++++ tools/objtool/klp-symid.c | 117 ++++++++++++++++++++++++++++++++ 10 files changed, 166 insertions(+), 1 deletion(-) create mode 100644 tools/objtool/klp-symid.c (limited to 'scripts') diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 5659f4b5a125..ee9c5d354a85 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -839,12 +839,20 @@ .stab.index 0 : { *(.stab.index) } \ .stab.indexstr 0 : { *(.stab.indexstr) } +#ifdef CONFIG_KLP_BUILD +#define KLP_SYMID \ + .klp.symid 0 : { *(.klp.symid) } +#else +#define KLP_SYMID +#endif + /* Required sections not related to debugging. */ #define ELF_DETAILS \ .comment 0 : { *(.comment) } \ .symtab 0 : { *(.symtab) } \ .strtab 0 : { *(.strtab) } \ - .shstrtab 0 : { *(.shstrtab) } + .shstrtab 0 : { *(.shstrtab) } \ + KLP_SYMID #define MODINFO \ .modinfo : { *(.modinfo) . = ALIGN(8); } diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o index 527352c222ff..24a3a4fd271c 100644 --- a/scripts/Makefile.vmlinux_o +++ b/scripts/Makefile.vmlinux_o @@ -47,6 +47,9 @@ endif vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION) += --noinstr \ $(if $(or $(CONFIG_MITIGATION_UNRET_ENTRY),$(CONFIG_MITIGATION_SRSO)), --unret) +# Only used for builds initiated by klp-build +vmlinux-objtool-args-$(if $(KLP_SYMIDS),y) += --klp-symids + objtool-args = $(vmlinux-objtool-args-y) --link # Link of vmlinux.o used for section mismatch analysis diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build index a8c103ce7763..f94e324ff53c 100755 --- a/scripts/livepatch/klp-build +++ b/scripts/livepatch/klp-build @@ -271,6 +271,9 @@ validate_config() { [[ -v CONFIG_GCC_PLUGIN_RANDSTRUCT ]] && \ die "kernel option 'CONFIG_GCC_PLUGIN_RANDSTRUCT' not supported" + [[ -v CONFIG_LD_DEAD_CODE_DATA_ELIMINATION ]] && \ + die "kernel option 'CONFIG_LD_DEAD_CODE_DATA_ELIMINATION' not supported" + [[ -v CONFIG_AS_IS_LLVM ]] && \ [[ "$CONFIG_AS_VERSION" -lt 200000 ]] && \ die "Clang assembler version < 20 not supported" @@ -555,6 +558,8 @@ build_kernel() { # cmd+=("KBUILD_MODPOST_WARN=1") + cmd+=("KLP_SYMIDS=1") + if [[ -v VERBOSE ]]; then cmd+=("V=1") else diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index a7b72a81d248..027944fe35b4 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -767,6 +767,7 @@ static const char *const section_white_list[] = ".llvm.call-graph-profile", /* call graph */ "__llvm_covfun", "__llvm_covmap", + ".klp.symid", /* objtool --klp-symids */ NULL }; diff --git a/tools/objtool/Build b/tools/objtool/Build index 93a37b0dfd31..506f89bed808 100644 --- a/tools/objtool/Build +++ b/tools/objtool/Build @@ -6,6 +6,7 @@ objtool-y += check.o objtool-y += special.o objtool-y += builtin-check.o objtool-y += elf.o +objtool-y += klp-symid.o objtool-y += objtool.o objtool-$(BUILD_DISAS) += disas.o diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c index 118c3de2f293..75b11dc85010 100644 --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -76,6 +76,7 @@ static const struct option check_options[] = { OPT_STRING_OPTARG('d', "disas", &opts.disas, "function-pattern", "disassemble functions", "*"), OPT_CALLBACK_OPTARG('h', "hacks", NULL, NULL, "jump_label,noinstr,skylake", "patch toolchain bugs/limitations", parse_hacks), OPT_BOOLEAN('i', "ibt", &opts.ibt, "validate and annotate IBT"), + OPT_BOOLEAN(0, "klp-symids", &opts.klp_symids, "generate .klp.symids for duplicate symbol disambiguation"), OPT_BOOLEAN('m', "mcount", &opts.mcount, "annotate mcount/fentry calls for ftrace"), OPT_BOOLEAN(0, "noabs", &opts.noabs, "reject absolute references in allocatable sections"), OPT_BOOLEAN('n', "noinstr", &opts.noinstr, "validate noinstr rules"), @@ -174,10 +175,16 @@ static bool opts_valid(void) return false; } + if (opts.klp_symids && !opts.link) { + ERROR("--klp-symids requires --link"); + return false; + } + if (opts.disas || opts.hack_jump_label || opts.hack_noinstr || opts.ibt || + opts.klp_symids || opts.mcount || opts.noabs || opts.noinstr || diff --git a/tools/objtool/check.c b/tools/objtool/check.c index f03dd59e7fca..a98d7589d8a4 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include #include @@ -4923,6 +4924,12 @@ int check(struct objtool_file *file) goto out; } + if (opts.klp_symids) { + ret = klp_create_symid_sections(file); + if (ret) + goto out; + } + if (opts.noabs) warnings += check_abs_references(file); diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h index e844e9c82b7b..349690bb1c50 100644 --- a/tools/objtool/include/objtool/builtin.h +++ b/tools/objtool/include/objtool/builtin.h @@ -16,6 +16,7 @@ struct opts { bool hack_noinstr; bool hack_skylake; bool ibt; + bool klp_symids; bool mcount; bool noabs; bool noinstr; diff --git a/tools/objtool/include/objtool/klp.h b/tools/objtool/include/objtool/klp.h index aab6db42052d..4d3c3bd462aa 100644 --- a/tools/objtool/include/objtool/klp.h +++ b/tools/objtool/include/objtool/klp.h @@ -31,6 +31,21 @@ struct klp_reloc { u32 type; }; +/* + * .klp.symid is used to correlate symbols between vmlinux.o and vmlinux, for + * calculating sympos to disambiguate duplicately-named symbols. + */ +#define KLP_SYMID_SEC ".klp.symid" + +struct klp_symid { + u64 id; + u64 addr; +}; + +struct objtool_file; + +int klp_create_symid_sections(struct objtool_file *file); + int cmd_klp_checksum(int argc, const char **argv); int cmd_klp_diff(int argc, const char **argv); int cmd_klp_post_link(int argc, const char **argv); diff --git a/tools/objtool/klp-symid.c b/tools/objtool/klp-symid.c new file mode 100644 index 000000000000..cf188cdfa607 --- /dev/null +++ b/tools/objtool/klp-symid.c @@ -0,0 +1,117 @@ +// 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 + +#include +#include +#include +#include + +static const char * const discarded_secs[] = { + ".discard", + ".modinfo", + "__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; +} -- cgit From 15fa203ef91e8a303c322eaaa8ca01a6ddaf94dc Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Sun, 2 Aug 2026 20:24:28 -0700 Subject: objtool/klp: Fix symbol resolution for duplicate data symbols 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: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files") Reported-by: Ben Procknow Reported-by: Joe Lawrence Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar 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 --- scripts/livepatch/klp-build | 4 + tools/objtool/Build | 3 +- tools/objtool/include/objtool/klp.h | 5 + tools/objtool/klp-diff.c | 66 +----- tools/objtool/klp-sympos.c | 411 ++++++++++++++++++++++++++++++++++++ 5 files changed, 427 insertions(+), 62 deletions(-) create mode 100644 tools/objtool/klp-sympos.c (limited to 'scripts') diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build index f94e324ff53c..b52a8489d9f6 100755 --- a/scripts/livepatch/klp-build +++ b/scripts/livepatch/klp-build @@ -611,6 +611,8 @@ copy_orig_objects() { done xtrace_restore + cp -f "$PWD/vmlinux" "$ORIG_DIR" || die "missing vmlinux" + mv -f "$TMP_DIR/build.log" "$ORIG_DIR" touch "$TIMESTAMP" touch "$ORIG_DIR/.complete" @@ -681,6 +683,8 @@ generate_checksums() { "$OBJTOOL" klp checksum "$dest" done + [[ -f "$src_dir/vmlinux" ]] && cp -f "$src_dir/vmlinux" "$dest_dir" + touch "$dest_dir/.complete" } diff --git a/tools/objtool/Build b/tools/objtool/Build index 506f89bed808..59f948628098 100644 --- a/tools/objtool/Build +++ b/tools/objtool/Build @@ -13,7 +13,8 @@ objtool-$(BUILD_DISAS) += disas.o objtool-$(BUILD_DISAS) += trace.o objtool-$(BUILD_ORC) += orc_gen.o orc_dump.o -objtool-$(BUILD_KLP) += builtin-klp.o klp-checksum.o klp-diff.o klp-post-link.o +objtool-$(BUILD_KLP) += builtin-klp.o klp-checksum.o klp-diff.o \ + klp-post-link.o klp-sympos.o objtool-y += libstring.o objtool-y += libctype.o diff --git a/tools/objtool/include/objtool/klp.h b/tools/objtool/include/objtool/klp.h index 4d3c3bd462aa..0118c2c170c3 100644 --- a/tools/objtool/include/objtool/klp.h +++ b/tools/objtool/include/objtool/klp.h @@ -43,9 +43,14 @@ struct klp_symid { }; struct objtool_file; +struct elf; +struct symbol; int klp_create_symid_sections(struct objtool_file *file); +int klp_sympos_init(struct elf *orig); +unsigned long klp_find_sympos(struct elf *elf, struct symbol *sym); + int cmd_klp_checksum(int argc, const char **argv); int cmd_klp_diff(int argc, const char **argv); int cmd_klp_post_link(int argc, const char **argv); diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c index 75ba0e060a34..c5284d275207 100644 --- a/tools/objtool/klp-diff.c +++ b/tools/objtool/klp-diff.c @@ -898,65 +898,6 @@ static int correlate_symbols(struct elfs *e) return 0; } -/* "sympos" is used by livepatch to disambiguate duplicate symbol names */ -static unsigned long find_sympos(struct elf *elf, struct symbol *sym) -{ - bool vmlinux = str_ends_with(objname, "vmlinux.o"); - unsigned long sympos = 0, nr_matches = 0; - bool has_dup = false; - struct symbol *s; - - if (sym->bind != STB_LOCAL) - return 0; - - if (vmlinux && is_func_sym(sym)) { - /* - * HACK: Unfortunately, symbol ordering can differ between - * vmlinux.o and vmlinux due to the linker script emitting - * .text.unlikely* before .text*. Count .text.unlikely* first. - * - * TODO: Disambiguate symbols more reliably (checksums?) - */ - for_each_sym(elf, s) { - if (strstarts(s->sec->name, ".text.unlikely") && - !strcmp(s->name, sym->name)) { - nr_matches++; - if (s == sym) - sympos = nr_matches; - else - has_dup = true; - } - } - for_each_sym(elf, s) { - if (!strstarts(s->sec->name, ".text.unlikely") && - !strcmp(s->name, sym->name)) { - nr_matches++; - if (s == sym) - sympos = nr_matches; - else - has_dup = true; - } - } - } else { - for_each_sym(elf, s) { - if (!strcmp(s->name, sym->name)) { - nr_matches++; - if (s == sym) - sympos = nr_matches; - else - has_dup = true; - } - } - } - - if (!sympos) { - ERROR("can't find sympos for %s", sym->name); - return ULONG_MAX; - } - - return has_dup ? sympos : 0; -} - static int clone_sym_relocs(struct elfs *e, struct symbol *patched_sym); static struct symbol *__clone_symbol(struct elf *elf, struct symbol *patched_sym, @@ -1418,7 +1359,7 @@ static int clone_reloc_klp(struct elfs *e, struct reloc *patched_reloc, return -1; sym_orig_name = patched_sym->twin->name; - sympos = find_sympos(e->orig, patched_sym->twin); + sympos = klp_find_sympos(e->orig, patched_sym->twin); if (sympos == ULONG_MAX) return -1; } @@ -2036,7 +1977,7 @@ static int create_klp_sections(struct elfs *e) /* klp_func_ext.sympos */ BUILD_BUG_ON(sizeof(sympos) != sizeof_field(struct klp_func_ext, sympos)); - sympos = find_sympos(e->orig, sym->clone->twin); + sympos = klp_find_sympos(e->orig, sym->clone->twin); if (sympos == ULONG_MAX) return -1; memcpy(func_data + offsetof(struct klp_func_ext, sympos), &sympos, @@ -2190,6 +2131,9 @@ int cmd_klp_diff(int argc, const char **argv) if (!e.orig || !e.patched) return -1; + if (klp_sympos_init(e.orig)) + return -1; + if (read_exports()) return -1; diff --git a/tools/objtool/klp-sympos.c b/tools/objtool/klp-sympos.c new file mode 100644 index 000000000000..bbfae516d339 --- /dev/null +++ b/tools/objtool/klp-sympos.c @@ -0,0 +1,411 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Compute "sympos", the position used by livepatch to disambiguate + * duplicate symbol names in the patched object. + */ +#include +#include +#include + +#include +#include +#include +#include + +#include + +struct vmlinux_sym { + struct hlist_node hash; + const char *name; + u64 addr; +}; + +struct vmlinux_symid { + struct hlist_node hash; + u64 id; + u64 addr; +}; + +struct vmlinux_o_symid { + struct hlist_node hash; + u64 id; + unsigned int sym_idx; +}; + +static DEFINE_HASHTABLE(vmlinux_o_symids, 16); + +/* + * The original linked kernel, found next to the orig vmlinux.o. Read with raw + * libelf rather than elf_open_read(): only the symbol table and the resolved + * .klp.symid table are needed, not the (huge) instruction/reloc machinery. + * + * Both tables are built once by read_orig_vmlinux(). The Elf handle stays + * open because the hashed names point into its mmapped string table. + */ +static struct { + Elf *elf; + DECLARE_HASHTABLE(syms, 16); /* name -> address */ + DECLARE_HASHTABLE(symids, 16); /* .klp.symid id -> address */ +} vmlinux; + +/* + * Would the symbol be visible to the runtime's kallsyms-based symbol lookup? + */ +static bool vmlinux_sym_in_kallsyms(Elf *elf, GElf_Sym *sym) +{ + unsigned int type = GELF_ST_TYPE(sym->st_info); + GElf_Shdr shdr; + Elf_Scn *scn; + + if (sym->st_shndx == SHN_UNDEF || sym->st_shndx >= SHN_LORESERVE) + return false; + + if (type == STT_SECTION || type == STT_FILE) + return false; + + scn = elf_getscn(elf, sym->st_shndx); + if (!scn || !gelf_getshdr(scn, &shdr)) + return false; + + return shdr.sh_flags & SHF_ALLOC; +} + +static int read_orig_vmlinux(const char *filename) +{ + size_t shstrndx, nr_syms = 0, nr_symids = 0, strtab_idx = 0; + Elf_Data *symtab_data = NULL, *symid_data = NULL; + struct klp_symid *symids; + Elf_Scn *scn = NULL; + GElf_Ehdr ehdr; + int fd; + + fd = open(filename, O_RDONLY); + if (fd == -1) { + ERROR_GLIBC("can't open '%s'", filename); + return -1; + } + + if (elf_version(EV_CURRENT) == EV_NONE) { + ERROR_ELF("elf_version"); + return -1; + } + + vmlinux.elf = elf_begin(fd, ELF_C_READ_MMAP, NULL); + if (!vmlinux.elf) { + ERROR_ELF("elf_begin"); + return -1; + } + + if (!gelf_getehdr(vmlinux.elf, &ehdr)) { + ERROR_ELF("gelf_getehdr"); + return -1; + } + + if (elf_getshdrstrndx(vmlinux.elf, &shstrndx)) { + ERROR_ELF("elf_getshdrstrndx"); + return -1; + } + + while ((scn = elf_nextscn(vmlinux.elf, scn))) { + const char *name; + GElf_Shdr shdr; + + if (!gelf_getshdr(scn, &shdr)) { + ERROR_ELF("gelf_getshdr"); + return -1; + } + + if (shdr.sh_type == SHT_SYMTAB) { + symtab_data = elf_getdata(scn, NULL); + if (!symtab_data) { + ERROR_ELF("elf_getdata"); + return -1; + } + nr_syms = shdr.sh_size / shdr.sh_entsize; + strtab_idx = shdr.sh_link; + continue; + } + + name = elf_strptr(vmlinux.elf, shstrndx, shdr.sh_name); + if (name && !strcmp(name, KLP_SYMID_SEC)) { + if (shdr.sh_size % sizeof(struct klp_symid)) { + ERROR("%s: %s: struct klp_symid size mismatch", + filename, KLP_SYMID_SEC); + return -1; + } + symid_data = elf_getdata(scn, NULL); + if (!symid_data) { + ERROR_ELF("elf_getdata"); + return -1; + } + nr_symids = shdr.sh_size / sizeof(struct klp_symid); + } + } + + if (!symtab_data) { + ERROR("%s: missing symbol table", filename); + return -1; + } + + if (!symid_data) { + ERROR("%s: missing %s section, kernel not built with CONFIG_KLP_BUILD?", + filename, KLP_SYMID_SEC); + return -1; + } + + for (size_t i = 0; i < nr_syms; i++) { + struct vmlinux_sym *vsym; + const char *name; + GElf_Sym s; + + if (!gelf_getsym(symtab_data, i, &s)) { + ERROR_ELF("gelf_getsym"); + return -1; + } + + if (!vmlinux_sym_in_kallsyms(vmlinux.elf, &s)) + continue; + + name = elf_strptr(vmlinux.elf, strtab_idx, s.st_name); + if (!name) + continue; + + vsym = calloc(1, sizeof(*vsym)); + if (!vsym) { + ERROR_GLIBC("calloc"); + return -1; + } + + vsym->name = name; + vsym->addr = s.st_value; + hash_add(vmlinux.syms, &vsym->hash, str_hash(name)); + } + + symids = symid_data->d_buf; + + for (size_t i = 0; i < nr_symids; i++) { + struct vmlinux_symid *vsymid; + + vsymid = calloc(1, sizeof(*vsymid)); + if (!vsymid) { + ERROR_GLIBC("calloc"); + return -1; + } + + vsymid->id = __bswap_if_needed(&ehdr, symids[i].id); + vsymid->addr = __bswap_if_needed(&ehdr, symids[i].addr); + hash_add(vmlinux.symids, &vsymid->hash, vsymid->id); + } + + /* the fd and Elf handle stay open, the hashed names live in the mmap */ + return 0; +} + +/* + * Read the orig vmlinux.o's .klp.symid table, an array of entries whose 'addr' + * fields have relocs to the symbols they describe. + */ +static int read_vmlinux_o_symids(struct elf *vmlinux_o) +{ + struct section *sec; + + for_each_sec(vmlinux_o, sec) { + unsigned long nr; + + if (strcmp(sec->name, KLP_SYMID_SEC)) + continue; + + if (sec_size(sec) % sizeof(struct klp_symid)) { + ERROR("%s: %s: struct klp_symid size mismatch", + vmlinux_o->name, KLP_SYMID_SEC); + return -1; + } + + nr = sec_size(sec) / sizeof(struct klp_symid); + + for (unsigned long i = 0; i < nr; i++) { + unsigned long offset = i * sizeof(struct klp_symid); + struct vmlinux_o_symid *entry; + struct klp_symid *symid; + struct reloc *reloc; + + entry = calloc(1, sizeof(*entry)); + if (!entry) { + ERROR_GLIBC("calloc"); + return -1; + } + + symid = sec->data->d_buf + offset; + entry->id = bswap_if_needed(vmlinux_o, symid->id); + + reloc = find_reloc_by_dest(vmlinux_o, sec, + offset + offsetof(struct klp_symid, addr)); + if (!reloc) { + ERROR("%s: missing reloc for %s entry", + vmlinux_o->name, KLP_SYMID_SEC); + return -1; + } + entry->sym_idx = reloc->sym->idx; + + hash_add(vmlinux_o_symids, &entry->hash, entry->sym_idx); + } + } + + return 0; +} + +int klp_sympos_init(struct elf *orig) +{ + char *filename; + int ret; + + if (!str_ends_with(objname, "vmlinux.o")) + return 0; + + if (read_vmlinux_o_symids(orig)) + return -1; + + filename = strndup(objname, strlen(objname) - 2); + if (!filename) { + ERROR_GLIBC("strndup"); + return -1; + } + + ret = read_orig_vmlinux(filename); + free(filename); + + return ret; +} + +/* Find the symbol's id in the orig vmlinux.o's .klp.symid table */ +static int find_vmlinux_o_symid(struct symbol *sym, u64 *id) +{ + struct vmlinux_o_symid *entry; + + hash_for_each_possible(vmlinux_o_symids, entry, hash, sym->idx) { + if (entry->sym_idx == sym->idx) { + *id = entry->id; + return 0; + } + } + + ERROR("no %s entry for symbol %s in orig vmlinux.o", KLP_SYMID_SEC, + sym->name); + return -1; +} + +/* Find the symbol's final address in the orig vmlinux's .klp.symid table */ +static int find_vmlinux_symid_addr(u64 id, u64 *addr) +{ + struct vmlinux_symid *symid; + + hash_for_each_possible(vmlinux.symids, symid, hash, id) { + if (symid->id == id) { + *addr = symid->addr; + return 0; + } + } + + return -1; +} + +/* + * Find the sympos of a vmlinux-local symbol by ranking its final address + * among the duplicately named symbols in the linked orig vmlinux, replicating + * the order in which kallsyms_on_each_match_symbol() counts them. + */ +static unsigned long find_vmlinux_sympos(struct symbol *sym) +{ + unsigned long nr_matches = 0, sympos = 1; + u32 key = str_hash(sym->name); + struct vmlinux_sym *vsym; + bool found = false; + u64 id, addr; + + hash_for_each_possible(vmlinux.syms, vsym, hash, key) + if (!strcmp(vsym->name, sym->name)) + nr_matches++; + + if (!nr_matches) { + ERROR("can't find symbol %s in orig vmlinux", sym->name); + return ULONG_MAX; + } + + /* + * Unique symbols don't need disambiguating. They also have no + * .klp.symid entry, which is only emitted for names duplicated in + * vmlinux.o, so the lookups below would fail. + */ + if (nr_matches == 1) + return 0; + + if (find_vmlinux_o_symid(sym, &id)) + return ULONG_MAX; + + if (find_vmlinux_symid_addr(id, &addr)) { + ERROR("no %s entry for symbol %s in orig vmlinux", KLP_SYMID_SEC, + sym->name); + return ULONG_MAX; + } + + hash_for_each_possible(vmlinux.syms, vsym, hash, key) { + if (strcmp(vsym->name, sym->name)) + continue; + + if (vsym->addr < addr) + sympos++; + else if (vsym->addr == addr) + found = true; + } + + if (!found) { + ERROR("%s address mismatch for symbol %s, stale orig vmlinux?", + KLP_SYMID_SEC, sym->name); + return ULONG_MAX; + } + + return sympos; +} + +/* + * "sympos" is used by livepatch to disambiguate duplicate symbol names. + */ +unsigned long klp_find_sympos(struct elf *elf, struct symbol *sym) +{ + unsigned long sympos = 0, nr_matches = 0; + bool has_dup = false; + struct symbol *s; + + if (sym->bind != STB_LOCAL) + return 0; + + /* + * vmlinux: the final link reorders symbols relative to vmlinux.o, + * so the position needs to be derived from the linked orig vmlinux via + * the .klp.symid table. + */ + if (vmlinux.elf) + return find_vmlinux_sympos(sym); + + /* + * modules: the final .ko preserves symbol table order, so a + * symtab-order count here matches the runtime count done by + * module_kallsyms_on_each_symbol(). + */ + for_each_sym(elf, s) { + if (!strcmp(s->name, sym->name)) { + nr_matches++; + if (s == sym) + sympos = nr_matches; + else + has_dup = true; + } + } + + if (!sympos) { + ERROR("can't find sympos for %s", sym->name); + return ULONG_MAX; + } + + return has_dup ? sympos : 0; +} -- cgit