Error out if a duplicate prefix symbol is attempted.

Signed-off-by: Josh Poimboeuf <jpoim...@kernel.org>
---
 tools/objtool/check.c               | 5 ++++-
 tools/objtool/elf.c                 | 9 +++++++++
 tools/objtool/include/objtool/elf.h | 3 +++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index af945854dd72..236dc7871f01 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3866,6 +3866,7 @@ static void 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)
@@ -3879,7 +3880,9 @@ static void 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)
+                       ERROR("duplicate prefix symbol for %s\n", func->name);
 
                break;
        }
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 0c95d7cdf0f5..748c170b931a 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -767,11 +767,20 @@ 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 e91bbe7f07bf..5ac5e7cdddee 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -399,6 +399,9 @@ static inline void set_reloc_type(struct elf *elf, struct 
reloc *reloc, unsigned
 #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 for_each_sym(elf, sym)                                         \
        for (struct section *__sec, *__fake = (struct section *)1;      \
             __fake; __fake = NULL)                                     \
-- 
2.45.2


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