objtool/klp: Use sym->demangled_name for symbol_name hash

For klp-build with LTO, it is necessary to correlate demangled symbols,
e.g., correlate foo.llvm.<num 1> and foo.llvm.<num 2>. However, these two
symbols do not have the same str_hash(name). To be able to correlate the
two symbols, calculate hash based on demanged_name, so that these two
symbols have the same hash.

No functional changes intended.

Signed-off-by: Song Liu <song@kernel.org>
Link: https://patch.msgid.link/20260305231531.3847295-4-song@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index fe6e66dd5422789e2629a6c40737b78dec25365e..b2d73c4c6cf19795eb0822d344c56ae1e6e31fd0 100644 (file)
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -26,11 +26,18 @@
 #include <objtool/elf.h>
 #include <objtool/warn.h>
 
+static ssize_t demangled_name_len(const char *name);
+
 static inline u32 str_hash(const char *str)
 {
        return jhash(str, strlen(str), 0);
 }
 
+static inline u32 str_hash_demangled(const char *str)
+{
+       return jhash(str, demangled_name_len(str), 0);
+}
+
 #define __elf_table(name)      (elf->name##_hash)
 #define __elf_bits(name)       (elf->name##_bits)
 
@@ -294,7 +301,7 @@ static struct symbol *find_local_symbol_by_file_and_name(const struct elf *elf,
 {
        struct symbol *sym;
 
-       elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(name)) {
+       elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash_demangled(name)) {
                if (sym->bind == STB_LOCAL && sym->file == file &&
                    !strcmp(sym->name, name)) {
                        return sym;
@@ -308,7 +315,7 @@ struct symbol *find_global_symbol_by_name(const struct elf *elf, const char *nam
 {
        struct symbol *sym;
 
-       elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash(name)) {
+       elf_hash_for_each_possible(symbol_name, sym, name_hash, str_hash_demangled(name)) {
                if (!strcmp(sym->name, name) && !is_local_sym(sym))
                        return sym;
        }
@@ -441,6 +448,28 @@ static int read_sections(struct elf *elf)
        return 0;
 }
 
+/*
+ * Returns desired length of the demangled name.
+ * If name doesn't need demangling, return strlen(name).
+ */
+static ssize_t demangled_name_len(const char *name)
+{
+       ssize_t idx;
+
+       if (!strstarts(name, "__UNIQUE_ID_") && !strchr(name, '.'))
+               return strlen(name);
+
+       for (idx = strlen(name) - 1; idx >= 0; idx--) {
+               char c = name[idx];
+
+               if (!isdigit(c) && c != '.' && c != '_')
+                       break;
+       }
+       if (idx <= 0)
+               return strlen(name);
+       return idx + 1;
+}
+
 /*
  * Remove number suffix of a symbol.
  *
@@ -457,6 +486,7 @@ static int read_sections(struct elf *elf)
 static const char *demangle_name(struct symbol *sym)
 {
        char *str;
+       ssize_t len;
 
        if (!is_local_sym(sym))
                return sym->name;
@@ -464,24 +494,16 @@ static const char *demangle_name(struct symbol *sym)
        if (!is_func_sym(sym) && !is_object_sym(sym))
                return sym->name;
 
-       if (!strstarts(sym->name, "__UNIQUE_ID_") && !strchr(sym->name, '.'))
+       len = demangled_name_len(sym->name);
+       if (len == strlen(sym->name))
                return sym->name;
 
-       str = strdup(sym->name);
+       str = strndup(sym->name, len);
        if (!str) {
                ERROR_GLIBC("strdup");
                return NULL;
        }
 
-       for (int i = strlen(str) - 1; i >= 0; i--) {
-               char c = str[i];
-
-               if (!isdigit(c) && c != '.' && c != '_') {
-                       str[i + 1] = '\0';
-                       break;
-               }
-       }
-
        return str;
 }
 
@@ -517,9 +539,13 @@ static int elf_add_symbol(struct elf *elf, struct symbol *sym)
                entry = &sym->sec->symbol_list;
        list_add(&sym->list, entry);
 
+       sym->demangled_name = demangle_name(sym);
+       if (!sym->demangled_name)
+               return -1;
+
        list_add_tail(&sym->global_list, &elf->symbols);
        elf_hash_add(symbol, &sym->hash, sym->idx);
-       elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->name));
+       elf_hash_add(symbol_name, &sym->name_hash, str_hash(sym->demangled_name));
 
        if (is_func_sym(sym) &&
            (strstarts(sym->name, "__pfx_") ||
@@ -543,10 +569,6 @@ static int elf_add_symbol(struct elf *elf, struct symbol *sym)
 
        sym->pfunc = sym->cfunc = sym;
 
-       sym->demangled_name = demangle_name(sym);
-       if (!sym->demangled_name)
-               return -1;
-
        return 0;
 }