[RFC PATCH 07/14] objtool: Warn about non __ro_after_init static key usage in .noinstr
From: Valentin Schneider <vschneid@redhat.com>
Date: 2023-07-05 18:18:03
Also in:
bpf, kvm, linux-mm, linux-trace-kernel, lkml
Subsystem:
objtool, the rest · Maintainers:
Josh Poimboeuf, Peter Zijlstra, Linus Torvalds
Later commits will depend on having no runtime-mutable text in early entry code. (ab)use the .noinstr section as a marker of early entry code and warn about static keys used in it that can be flipped at runtime. Suggested-by: Josh Poimboeuf <redacted> Signed-off-by: Valentin Schneider <vschneid@redhat.com> --- tools/objtool/check.c | 20 ++++++++++++++++++++ tools/objtool/include/objtool/check.h | 1 + tools/objtool/include/objtool/special.h | 2 ++ tools/objtool/special.c | 3 +++ 4 files changed, 26 insertions(+)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index fe62232f218f9..7f8d210ec88c3 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c@@ -2032,6 +2032,9 @@ static int add_special_section_alts(struct objtool_file *file) alt->next = orig_insn->alts; orig_insn->alts = alt; + if (special_alt->key_sym) + orig_insn->key_sym = special_alt->key_sym; + list_del(&special_alt->list); free(special_alt); }
@@ -3520,6 +3523,20 @@ static int validate_return(struct symbol *func, struct instruction *insn, struct return 0; } +static int validate_static_key(struct instruction *insn, struct insn_state *state) +{ + if (state->noinstr && state->instr <= 0) { + if ((strcmp(insn->key_sym->sec->name, ".data..ro_after_init"))) { + WARN_INSN(insn, + "Non __ro_after_init static key \"%s\" in .noinstr section", + insn->key_sym->name); + return 1; + } + } + + return 0; +} + static struct instruction *next_insn_to_validate(struct objtool_file *file, struct instruction *insn) {
@@ -3670,6 +3687,9 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, if (handle_insn_ops(insn, next_insn, &state)) return 1; + if (insn->key_sym) + validate_static_key(insn, &state); + switch (insn->type) { case INSN_RETURN:
diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index daa46f1f0965a..35dd21f8f41e1 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h@@ -77,6 +77,7 @@ struct instruction { struct symbol *sym; struct stack_op *stack_ops; struct cfi_state *cfi; + struct symbol *key_sym; }; static inline struct symbol *insn_func(struct instruction *insn)
diff --git a/tools/objtool/include/objtool/special.h b/tools/objtool/include/objtool/special.h
index 86d4af9c5aa9d..0e61f34fe3a28 100644
--- a/tools/objtool/include/objtool/special.h
+++ b/tools/objtool/include/objtool/special.h@@ -27,6 +27,8 @@ struct special_alt { struct section *new_sec; unsigned long new_off; + struct symbol *key_sym; + unsigned int orig_len, new_len; /* group only */ };
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index baa85c31526b3..830e6abf173a2 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c@@ -127,6 +127,9 @@ static int get_alt_entry(struct elf *elf, const struct special_entry *entry, return -1; } alt->key_addend = key_reloc->addend; + + reloc_to_sec_off(key_reloc, &sec, &offset); + alt->key_sym = find_symbol_by_offset(sec, offset & ~2); } return 0;
--
2.31.1