objtool: Refactor function alias logic

- 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@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/26a99c31426540f19c9a58b9e10727c385a147bc.1563413318.git.jpoimboe@redhat.com

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index d8a1ce8..3f8664b 100644 (file)
--- 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 e186982..9194732 100644 (file)
--- 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) {