[PATCH 18/25] objtool: Handle function aliases

[Peter Zijlstra]

Function aliases result in different symbols for the same set of
instructions; track a canonical symbol so there is a unique point of
access.

This again prepares the way for function attributes. And in particular
the need for aliases comes from how KASAN uses them.

Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
 tools/objtool/elf.c |   15 +++++++++++----
 tools/objtool/elf.h |    2 +-
 2 files changed, 12 insertions(+), 5 deletions(-)

--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -219,7 +219,7 @@ static int read_sections(struct elf *elf
 static int read_symbols(struct elf *elf)
 {
        struct section *symtab, *sec;
-       struct symbol *sym, *pfunc;
+       struct symbol *sym, *pfunc, *alias;
        struct list_head *entry, *tmp;
        int symbols_nr, i;
        char *coldstr;
@@ -239,6 +239,7 @@ static int read_symbols(struct elf *elf)
                        return -1;
                }
                memset(sym, 0, sizeof(*sym));
+               alias = sym;
 
                sym->idx = i;
 
@@ -288,11 +289,17 @@ static int read_symbols(struct elf *elf)
                                break;
                        }
 
-                       if (sym->offset == s->offset && sym->len >= s->len) {
-                               entry = tmp;
-                               break;
+                       if (sym->offset == s->offset) {
+                               if (sym->len == s->len && alias == sym)
+                                       alias = s;
+
+                               if (sym->len >= s->len) {
+                                       entry = tmp;
+                                       break;
+                               }
                        }
                }
+               sym->alias = alias;
                list_add(&sym->list, entry);
                hash_add(sym->sec->symbol_hash, &sym->hash, sym->idx);
        }
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -61,7 +61,7 @@ struct symbol {
        unsigned char bind, type;
        unsigned long offset;
        unsigned int len;
-       struct symbol *pfunc, *cfunc;
+       struct symbol *pfunc, *cfunc, *alias;
 };
 
 struct rela {