klp-diff treats all rodata as uncorrelated, so any reference to it uses a duplicated copy rather than using a KLP reloc.
For the contents of the data itself, a duplicated copy is fine. However, pointer comparisons (e.g., f->f_op == &foo_ops) are broken. Fix it by correlating non-anonymous rodata objects. Also, use a new find_symbol_containing_inclusive() helper for matching the end of a symbol so bounds calculations don't get broken, for the case where an array or other symbol's ending address is used as part of a bounds calculation. While these are really two distinct changes, they need to be done in the same patch so as to avoid introducing bisection regressions. Signed-off-by: Josh Poimboeuf <[email protected]> --- tools/objtool/elf.c | 14 ++++++++++++++ tools/objtool/include/objtool/elf.h | 1 + tools/objtool/klp-diff.c | 15 +++++++++++++-- 3 files changed, 28 insertions(+), 2 deletions(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 87c6e00749c6..5a20dab683dd 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -207,6 +207,20 @@ struct symbol *find_symbol_containing(const struct section *sec, unsigned long o return sym ? sym->alias : NULL; } +/* + * Also match the symbol end address which can be used for a bounds comparison. + */ +struct symbol *find_symbol_containing_inclusive(const struct section *sec, + unsigned long offset) +{ + struct symbol *sym = find_symbol_containing(sec, offset); + + if (!sym && offset) + sym = find_symbol_containing(sec, offset - 1); + + return sym; +} + /* * Returns size of hole starting at @offset. */ diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h index ab5f7017ec34..8a543cea43b9 100644 --- a/tools/objtool/include/objtool/elf.h +++ b/tools/objtool/include/objtool/elf.h @@ -211,6 +211,7 @@ struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset); struct symbol *find_symbol_by_name(const struct elf *elf, const char *name); struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *name); struct symbol *find_symbol_containing(const struct section *sec, unsigned long offset); +struct symbol *find_symbol_containing_inclusive(const struct section *sec, unsigned long offset); int find_symbol_hole_containing(const struct section *sec, unsigned long offset); struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, unsigned long offset); struct reloc *find_reloc_by_dest_range(const struct elf *elf, struct section *sec, diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c index 78633c9b68eb..bf37c652188b 100644 --- a/tools/objtool/klp-diff.c +++ b/tools/objtool/klp-diff.c @@ -386,6 +386,7 @@ static bool dont_correlate(struct symbol *sym) is_uncorrelated_static_local(sym) || is_local_label(sym) || is_string_sec(sym->sec) || + (is_rodata_sec(sym->sec) && !is_object_sym(sym)) || is_initcall_sym(sym) || is_addressable_sym(sym) || is_special_section(sym->sec) || @@ -979,7 +980,7 @@ static int convert_reloc_secsym_to_sym(struct elf *elf, struct reloc *reloc) goto found_sym; /* No dedicated section; find the symbol manually */ - sym = find_symbol_containing(sec, arch_adjusted_addend(reloc)); + sym = find_symbol_containing_inclusive(sec, arch_adjusted_addend(reloc)); if (!sym) { /* * This is presumably an .altinstr_replacement section which is @@ -988,6 +989,17 @@ static int convert_reloc_secsym_to_sym(struct elf *elf, struct reloc *reloc) if (!sec_size(sec)) return 1; + /* + * .rodata is a mixed bag of named objects and anonymous data. + * + * Convert section symbol references to named object symbols + * when possible, to preserve pointer identity for const + * structs like file_operations. Otherwise a section symbol is + * fine. + */ + if (is_rodata_sec(sec)) + return 0; + /* * This can happen for special section references to weak code * whose symbol has been stripped by the linker. @@ -1009,7 +1021,6 @@ static int convert_reloc_secsym_to_sym(struct elf *elf, struct reloc *reloc) static bool is_uncorrelated_section(struct section *sec) { return is_string_sec(sec) || - strstarts(sec->name, ".rodata") || strstarts(sec->name, ".data..Lubsan") || /* GCC */ strstarts(sec->name, ".data..L__unnamed_"); /* Clang */ } -- 2.53.0
