objtool: Identify the different types of alternatives

Alternative code, including jump table and exception table, is represented
with the same struct alternative structure. But there is no obvious way to
identify whether the struct represents alternative instructions, a jump
table or an exception table.

So add a type to struct alternative to clearly identify the type of
alternative.

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-14-alexandre.chartre@oracle.com

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index a02f8db75827f4279361b36dec2f7a27928834ea..93aaa4b5dce0eac582387287f3b67d9dac7d74ac 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -27,11 +27,6 @@
 #include <linux/static_call_types.h>
 #include <linux/string.h>
 
-struct alternative {
-       struct alternative *next;
-       struct instruction *insn;
-};
-
 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
 
 static struct cfi_init_state initial_func_cfi;
@@ -1924,6 +1919,7 @@ static int add_special_section_alts(struct objtool_file *file)
        struct list_head special_alts;
        struct instruction *orig_insn, *new_insn;
        struct special_alt *special_alt, *tmp;
+       enum alternative_type alt_type;
        struct alternative *alt;
 
        if (special_get_alts(file->elf, &special_alts))
@@ -1959,9 +1955,15 @@ static int add_special_section_alts(struct objtool_file *file)
                        if (handle_group_alt(file, special_alt, orig_insn, &new_insn))
                                return -1;
 
+                       alt_type = ALT_TYPE_INSTRUCTIONS;
+
                } else if (special_alt->jump_or_nop) {
                        if (handle_jump_alt(file, special_alt, orig_insn, &new_insn))
                                return -1;
+
+                       alt_type = ALT_TYPE_JUMP_TABLE;
+               } else {
+                       alt_type = ALT_TYPE_EX_TABLE;
                }
 
                alt = calloc(1, sizeof(*alt));
@@ -1972,6 +1974,7 @@ static int add_special_section_alts(struct objtool_file *file)
 
                alt->insn = new_insn;
                alt->next = orig_insn->alts;
+               alt->type = alt_type;
                orig_insn->alts = alt;
 
                list_del(&special_alt->list);

diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index fde958683485f20d2f17c411cae244f5b4da2262..cbf4af58e29b251a52a69f11935411f90a898b0b 100644 (file)
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -38,6 +38,18 @@ struct alt_group {
        bool ignore;
 };
 
+enum alternative_type {
+       ALT_TYPE_INSTRUCTIONS,
+       ALT_TYPE_JUMP_TABLE,
+       ALT_TYPE_EX_TABLE,
+};
+
+struct alternative {
+       struct alternative *next;
+       struct instruction *insn;
+       enum alternative_type type;
+};
+
 #define INSN_CHUNK_BITS                8
 #define INSN_CHUNK_SIZE                (1 << INSN_CHUNK_BITS)
 #define INSN_CHUNK_MAX         (INSN_CHUNK_SIZE - 1)