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objtool: Identify the different types of alternatives

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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
This commit is contained in:
Alexandre Chartre
2025-11-21 10:53:23 +01:00
committed by Peter Zijlstra
parent 26a453fb56
commit d490aa2197
2 changed files with 20 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
tools/objtool/check.c
View File

@@ -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);

12
tools/objtool/include/objtool/check.h
View File

@@ -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)