objtool: Remove annotate_{,un}reachable()

There are no users of annotate_reachable() left.

And the annotate_unreachable() usage in unreachable() is plain wrong;
it will hide dangerous fall-through code-gen.

Remove both.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20241128094312.235637588@infradead.org

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 7be80897a62f738f4850633fd794ffd8c4a8a1db..3d9a0e483e5127524b49e514cc3f8709299ee969 100644 (file)
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -109,35 +109,9 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 
 /* Unreachable code */
 #ifdef CONFIG_OBJTOOL
-/*
- * These macros help objtool understand GCC code flow for unreachable code.
- * The __COUNTER__ based labels are a hack to make each instance of the macros
- * unique, to convince GCC not to merge duplicate inline asm statements.
- */
-#define __stringify_label(n) #n
-
-#define __annotate_reachable(c) ({                                     \
-       asm volatile(__stringify_label(c) ":\n\t"                       \
-                       ".pushsection .discard.reachable\n\t"           \
-                       ".long " __stringify_label(c) "b - .\n\t"       \
-                       ".popsection\n\t");                             \
-})
-#define annotate_reachable() __annotate_reachable(__COUNTER__)
-
-#define __annotate_unreachable(c) ({                                   \
-       asm volatile(__stringify_label(c) ":\n\t"                       \
-                    ".pushsection .discard.unreachable\n\t"            \
-                    ".long " __stringify_label(c) "b - .\n\t"          \
-                    ".popsection\n\t" : : "i" (c));                    \
-})
-#define annotate_unreachable() __annotate_unreachable(__COUNTER__)
-
 /* Annotate a C jump table to allow objtool to follow the code flow */
 #define __annotate_jump_table __section(".rodata..c_jump_table,\"a\",@progbits #")
-
 #else /* !CONFIG_OBJTOOL */
-#define annotate_reachable()
-#define annotate_unreachable()
 #define __annotate_jump_table
 #endif /* CONFIG_OBJTOOL */
 
@@ -147,7 +121,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
  * control elsewhere.
  */
 #define unreachable() do {             \
-       annotate_unreachable();         \
        barrier_before_unreachable();   \
        __builtin_unreachable();        \
 } while (0)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 3bea8b2963d343b788d155d80a66d2919fb45e99..798cff5bffc42c3a41ff2748c311b9b9f2dd1308 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -638,47 +638,8 @@ static int add_dead_ends(struct objtool_file *file)
        uint64_t offset;
 
        /*
-        * Check for manually annotated dead ends.
-        */
-       rsec = find_section_by_name(file->elf, ".rela.discard.unreachable");
-       if (!rsec)
-               goto reachable;
-
-       for_each_reloc(rsec, reloc) {
-               if (reloc->sym->type == STT_SECTION) {
-                       offset = reloc_addend(reloc);
-               } else if (reloc->sym->local_label) {
-                       offset = reloc->sym->offset;
-               } else {
-                       WARN("unexpected relocation symbol type in %s", rsec->name);
-                       return -1;
-               }
-
-               insn = find_insn(file, reloc->sym->sec, offset);
-               if (insn)
-                       insn = prev_insn_same_sec(file, insn);
-               else if (offset == reloc->sym->sec->sh.sh_size) {
-                       insn = find_last_insn(file, reloc->sym->sec);
-                       if (!insn) {
-                               WARN("can't find unreachable insn at %s+0x%" PRIx64,
-                                    reloc->sym->sec->name, offset);
-                               return -1;
-                       }
-               } else {
-                       WARN("can't find unreachable insn at %s+0x%" PRIx64,
-                            reloc->sym->sec->name, offset);
-                       return -1;
-               }
-
-               insn->dead_end = true;
-       }
-
-reachable:
-       /*
-        * These manually annotated reachable checks are needed for GCC 4.4,
-        * where the Linux unreachable() macro isn't supported.  In that case
-        * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
-        * not a dead end.
+        * UD2 defaults to being a dead-end, allow them to be annotated for
+        * non-fatal, eg WARN.
         */
        rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
        if (!rsec)