[PATCH v2 55/62] objtool: Disallow duplicate prefix symbols

[Josh Poimboeuf]

In preparation for adding objtool 'check' support for analyzing
livepatch modules, error out if a duplicate prefix symbol is attempted.

Signed-off-by: Josh Poimboeuf <jpoim...@kernel.org>
---
 tools/objtool/check.c               | 12 +++++++++++-
 tools/objtool/elf.c                 |  9 +++++++++
 tools/objtool/include/objtool/elf.h |  3 +++
 3 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 30a5eb725931..bc9bc37efa55 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4271,6 +4271,7 @@ static int add_prefix_symbol(struct objtool_file *file, 
struct symbol *func)
        for (prev = prev_insn_same_sec(file, insn);
             prev;
             prev = prev_insn_same_sec(file, prev)) {
+               struct symbol *sym_pfx;
                u64 offset;
 
                if (prev->type != INSN_NOP)
@@ -4284,7 +4285,12 @@ static int add_prefix_symbol(struct objtool_file *file, 
struct symbol *func)
                if (offset < opts.prefix)
                        continue;
 
-               elf_create_prefix_symbol(file->elf, func, opts.prefix);
+               sym_pfx = elf_create_prefix_symbol(file->elf, func, 
opts.prefix);
+               if (!sym_pfx) {
+                       WARN("duplicate prefix symbol for %s\n", func->name);
+                       return -1;
+               }
+
                break;
        }
 
@@ -4320,6 +4326,10 @@ static int add_prefix_symbols(struct objtool_file *file)
                        if (!is_func_sym(func))
                                continue;
 
+                       /*
+                        * Ignore this error on purpose, there are valid
+                        * reasons for this to fail.
+                        */
                        add_prefix_symbol(file, func);
                }
        }
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 645f7ac12869..de1d8554d979 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -946,11 +946,20 @@ elf_create_prefix_symbol(struct elf *elf, struct symbol 
*orig, size_t size)
        size_t namelen = strlen(orig->name) + sizeof("__pfx_");
        char name[SYM_NAME_LEN];
        unsigned long offset;
+       struct symbol *sym;
 
        snprintf(name, namelen, "__pfx_%s", orig->name);
 
+       sym = orig;
        offset = orig->sym.st_value - size;
 
+       sec_for_each_sym_continue_reverse(orig->sec, sym) {
+               if (sym->offset < offset)
+                       break;
+               if (sym->offset == offset && !strcmp(sym->name, name))
+                       return NULL;
+       }
+
        return elf_create_symbol(elf, name, orig->sec,
                                 GELF_ST_BIND(orig->sym.st_info),
                                 GELF_ST_TYPE(orig->sym.st_info),
diff --git a/tools/objtool/include/objtool/elf.h 
b/tools/objtool/include/objtool/elf.h
index f62ac8081f27..1bf9c0a1112d 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -443,6 +443,9 @@ static inline void set_sym_next_reloc(struct reloc *reloc, 
struct reloc *next)
 #define sec_for_each_sym(sec, sym)                                     \
        list_for_each_entry(sym, &sec->symbol_list, list)
 
+#define sec_for_each_sym_continue_reverse(sec, sym)                    \
+       list_for_each_entry_continue_reverse(sym, &sec->symbol_list, list)
+
 #define sec_prev_sym(sym)                                              \
        sym->sec && sym->list.prev != &sym->sec->symbol_list ?          \
        list_prev_entry(sym, list) : NULL
-- 
2.49.0