[PATCH v2 13/22] objtool: Refactor function alias logic

From: Josh Poimboeuf
Date: Wed Jul 17 2019 - 21:38:27 EST


- Add an alias check in validate_functions(). With this change, aliases
no longer need uaccess_safe set.

- Add an alias check in decode_instructions(). With this change, the
"if (!insn->func)" check is no longer needed.

- Don't create aliases for zero-length functions, as it can have
unexpected results. The next patch will spit out a warning for
zero-length functions anyway.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
---
tools/objtool/check.c | 16 +++++++++-------
tools/objtool/elf.c | 2 +-
2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index bb9cfda670fd..9bf4844d9226 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -276,7 +276,7 @@ static int decode_instructions(struct objtool_file *file)
}

list_for_each_entry(func, &sec->symbol_list, list) {
- if (func->type != STT_FUNC)
+ if (func->type != STT_FUNC || func->alias != func)
continue;

if (!find_insn(file, sec, func->offset)) {
@@ -286,8 +286,7 @@ static int decode_instructions(struct objtool_file *file)
}

func_for_each_insn(file, func, insn)
- if (!insn->func)
- insn->func = func;
+ insn->func = func;
}
}

@@ -508,7 +507,7 @@ static void add_uaccess_safe(struct objtool_file *file)
if (!func)
continue;

- func->alias->uaccess_safe = true;
+ func->uaccess_safe = true;
}
}

@@ -1887,7 +1886,7 @@ static bool insn_state_match(struct instruction *insn, struct insn_state *state)
static inline bool func_uaccess_safe(struct symbol *func)
{
if (func)
- return func->alias->uaccess_safe;
+ return func->uaccess_safe;

return false;
}
@@ -2355,14 +2354,17 @@ static int validate_functions(struct objtool_file *file)

for_each_sec(file, sec) {
list_for_each_entry(func, &sec->symbol_list, list) {
- if (func->type != STT_FUNC || func->pfunc != func)
+ if (func->type != STT_FUNC)
+ continue;
+
+ if (func->pfunc != func || func->alias != func)
continue;

insn = find_insn(file, sec, func->offset);
if (!insn || insn->ignore || insn->visited)
continue;

- state.uaccess = func->alias->uaccess_safe;
+ state.uaccess = func->uaccess_safe;

ret = validate_branch(file, func, insn, state);
if (ret && backtrace)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index e99e1be19ad9..d2c211b0a5a0 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -278,7 +278,7 @@ static int read_symbols(struct elf *elf)
}

if (sym->offset == s->offset) {
- if (sym->len == s->len && alias == sym)
+ if (sym->len && sym->len == s->len && alias == sym)
alias = s;

if (sym->len >= s->len) {
--
2.20.1