[PATCH 18/25] objtool: Handle function aliases

From: Peter Zijlstra
Date: Mon Mar 18 2019 - 11:54:39 EST


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) <peterz@xxxxxxxxxxxxx>
---
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 {