objtool: Remove second pass of .cold function correlation

The .cold function parent/child correlation logic has two passes: one in
read_symbols() and one in add_jump_destinations().

The second pass was added with commit cd77849a69cf ("objtool: Fix GCC 8
cold subfunction detection for aliased functions") to ensure that if the
parent symbol had aliases then the canonical symbol was chosen as the
parent.

That solution was rather clunky, not to mention incomplete due to the
existence of alternatives and switch tables.  Now that we have
sym->alias, the canonical alias fix can be done much simpler in the
first pass, making the second pass obsolete.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/bdab245a38000a5407f663a031f39e14c67a43d4.1763671318.git.jpoimboe@kernel.org

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 6a4a29f8f2f50a6b326e7f26956afaed761d733f..1a20ff89df742f1f1710850b7bc31e01f8f61a2d 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1623,34 +1623,13 @@ static int add_jump_destinations(struct objtool_file *file)
                        continue;
                }
 
-               if (!insn->sym || insn->sym == dest_insn->sym)
+               if (!insn->sym || insn->sym->pfunc == dest_sym->pfunc)
                        goto set_jump_dest;
 
                /*
                 * Internal cross-function jump.
                 */
 
-               /*
-                * For GCC 8+, create parent/child links for any cold
-                * subfunctions.  This is _mostly_ redundant with a
-                * similar initialization in read_symbols().
-                *
-                * If a function has aliases, we want the *first* such
-                * function in the symbol table to be the subfunction's
-                * parent.  In that case we overwrite the
-                * initialization done in read_symbols().
-                *
-                * However this code can't completely replace the
-                * read_symbols() code because this doesn't detect the
-                * case where the parent function's only reference to a
-                * subfunction is through a jump table.
-                */
-               if (func && dest_sym->cold) {
-                       func->cfunc = dest_sym;
-                       dest_sym->pfunc = func;
-                       goto set_jump_dest;
-               }
-
                if (is_first_func_insn(file, dest_insn)) {
                        /* Internal sibling call */
                        if (add_call_dest(file, insn, dest_sym, true))

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 7e2c0ae6b41ac4acd9d9ce076b465e21023b1e83..6a8ed9c62323ea5f0225843c0b5886ad4353bab1 100644 (file)
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -658,8 +658,9 @@ static int read_symbols(struct elf *elf)
                                return -1;
                        }
 
-                       sym->pfunc = pfunc;
+                       sym->pfunc = pfunc->alias;
                        pfunc->cfunc = sym;
+                       pfunc->alias->cfunc = sym;
 
                        /*
                         * Unfortunately, -fnoreorder-functions puts the child