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Message-ID: <20251112160315.2207947-26-alexandre.chartre@oracle.com>
Date: Wed, 12 Nov 2025 17:03:12 +0100
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: linux-kernel@...r.kernel.org, mingo@...nel.org, jpoimboe@...nel.org,
peterz@...radead.org
Cc: alexandre.chartre@...cle.com
Subject: [PATCH v3 25/28] objtool: Improve naming of group alternatives
Improve the naming of group alternatives by showing the feature name and
flags used by the alternative.
Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com>
---
tools/objtool/check.c | 31 ++------
tools/objtool/disas.c | 106 ++++++++++++++++++++------
tools/objtool/include/objtool/disas.h | 2 +
3 files changed, 90 insertions(+), 49 deletions(-)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 89b35e8a068d0..1aad636a8d630 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3566,6 +3566,7 @@ static int validate_insn(struct objtool_file *file, struct symbol *func,
/* prev_state is not used if there is no disassembly support */
struct insn_state prev_state __maybe_unused;
struct alternative *alt;
+ char *alt_name = NULL;
u8 visited;
int ret;
@@ -3651,43 +3652,21 @@ static int validate_insn(struct objtool_file *file, struct symbol *func,
return 1;
if (insn->alts) {
- char alt_name[35];
- int i, num_alts;
-
- num_alts = 0;
- for (alt = insn->alts; alt; alt = alt->next) {
- if (alt->type == ALT_TYPE_INSTRUCTIONS)
- num_alts++;
- }
-
- i = 1;
for (alt = insn->alts; alt; alt = alt->next) {
if (trace) {
- switch (alt->type) {
- case ALT_TYPE_EX_TABLE:
- strcpy(alt_name, "EXCEPTION");
- break;
- case ALT_TYPE_JUMP_TABLE:
- strcpy(alt_name, "JUMP");
- break;
- case ALT_TYPE_INSTRUCTIONS:
- snprintf(alt_name, sizeof(alt_name),
- "ALTERNATIVE %d/%d", i, num_alts);
- break;
- }
+ alt_name = disas_alt_name(alt);
trace_alt_begin(insn, alt, alt_name);
}
ret = validate_branch(file, func, alt->insn, *statep);
- if (trace)
+ if (trace) {
trace_alt_end(insn, alt, alt_name);
+ free(alt_name);
+ }
if (ret) {
BT_INSN(insn, "(alt)");
return ret;
}
- if (alt->insn->alt_group)
- i++;
}
-
TRACE_ALT_INFO_NOADDR(insn, "/ ", "DEFAULT");
}
diff --git a/tools/objtool/disas.c b/tools/objtool/disas.c
index ae3b4d20cf35c..2a6c3708ec315 100644
--- a/tools/objtool/disas.c
+++ b/tools/objtool/disas.c
@@ -9,6 +9,7 @@
#include <objtool/arch.h>
#include <objtool/check.h>
#include <objtool/disas.h>
+#include <objtool/special.h>
#include <objtool/warn.h>
#include <bfd.h>
@@ -60,6 +61,21 @@ struct disas_alt {
#define DALT_GROUP(dalt) (DALT_INSN(dalt)->alt_group)
#define DALT_ALTID(dalt) ((dalt)->orig_insn->offset)
+#define ALT_FLAGS_SHIFT 16
+#define ALT_FLAG_NOT (1 << 0)
+#define ALT_FLAG_DIRECT_CALL (1 << 1)
+#define ALT_FEATURE_MASK ((1 << ALT_FLAGS_SHIFT) - 1)
+
+static int alt_feature(unsigned ft_flags)
+{
+ return (ft_flags & ALT_FEATURE_MASK);
+}
+
+static int alt_flags(unsigned ft_flags)
+{
+ return (ft_flags >> ALT_FLAGS_SHIFT);
+}
+
/*
* Wrapper around asprintf() to allocate and format a string.
* Return the allocated string or NULL on error.
@@ -588,38 +604,82 @@ static struct instruction *next_insn_same_alt(struct objtool_file *file,
insn; \
insn = next_insn_same_alt(file, alt_grp, insn))
+/*
+ * Provide a name for an alternative.
+ */
+char *disas_alt_name(struct alternative *alt)
+{
+ char pfx[4] = { 0 };
+ char *str = NULL;
+ const char *name;
+ int feature;
+ int flags;
+ int num;
+
+ switch (alt->type) {
+
+ case ALT_TYPE_EX_TABLE:
+ str = strdup("EXCEPTION");
+ break;
+
+ case ALT_TYPE_JUMP_TABLE:
+ str = strdup("JUMP");
+ break;
+
+ case ALT_TYPE_INSTRUCTIONS:
+ /*
+ * This is a non-default group alternative. Create a name
+ * based on the feature and flags associated with this
+ * alternative. Use either the feature name (it is available)
+ * or the feature number. And add a prefix to show the flags
+ * used.
+ *
+ * Prefix flags characters:
+ *
+ * '!' alternative used when feature not enabled
+ * '+' direct call alternative
+ * '?' unknown flag
+ */
+
+ feature = alt->insn->alt_group->feature;
+ num = alt_feature(feature);
+ flags = alt_flags(feature);
+ str = pfx;
+
+ if (flags & ~(ALT_FLAG_NOT | ALT_FLAG_DIRECT_CALL))
+ *str++ = '?';
+ if (flags & ALT_FLAG_DIRECT_CALL)
+ *str++ = '+';
+ if (flags & ALT_FLAG_NOT)
+ *str++ = '!';
+
+ name = arch_cpu_feature_name(num);
+ if (!name)
+ str = strfmt("%sFEATURE 0x%X", pfx, num);
+ else
+ str = strfmt("%s%s", pfx, name);
+
+ break;
+ }
+
+ return str;
+}
+
/*
* Initialize an alternative. The default alternative should be initialized
* with alt=NULL.
*/
static int disas_alt_init(struct disas_alt *dalt,
struct instruction *orig_insn,
- struct alternative *alt,
- int alt_num)
+ struct alternative *alt)
{
- char *str;
-
dalt->orig_insn = orig_insn;
dalt->alt = alt;
dalt->insn_idx = 0;
- if (!alt) {
- str = strfmt("<alternative.%lx>", orig_insn->offset);
- } else {
- switch (alt->type) {
- case ALT_TYPE_EX_TABLE:
- str = strdup("EXCEPTION");
- break;
- case ALT_TYPE_JUMP_TABLE:
- str = strdup("JUMP");
- break;
- default:
- str = strfmt("ALTERNATIVE %d", alt_num);
- break;
- }
- }
- if (!str)
+ dalt->name = alt ? disas_alt_name(alt) :
+ strfmt("<alternative.%lx>", orig_insn->offset);
+ if (!dalt->name)
return -1;
- dalt->name = str;
dalt->width = strlen(dalt->name);
return 0;
@@ -832,7 +892,7 @@ static void *disas_alt(struct disas_context *dctx,
/*
* Initialize and disassemble the default alternative.
*/
- err = disas_alt_init(&alts[0], orig_insn, NULL, 0);
+ err = disas_alt_init(&alts[0], orig_insn, NULL);
if (err)
goto error;
@@ -851,7 +911,7 @@ static void *disas_alt(struct disas_context *dctx,
break;
}
dalt = &alts[i];
- err = disas_alt_init(dalt, orig_insn, alt, i);
+ err = disas_alt_init(dalt, orig_insn, alt);
if (err)
goto error;
diff --git a/tools/objtool/include/objtool/disas.h b/tools/objtool/include/objtool/disas.h
index 5d2149ffac335..5272acd61dd03 100644
--- a/tools/objtool/include/objtool/disas.h
+++ b/tools/objtool/include/objtool/disas.h
@@ -6,6 +6,7 @@
#ifndef _DISAS_H
#define _DISAS_H
+struct alternative;
struct disas_context;
struct disassemble_info;
@@ -25,6 +26,7 @@ void disas_print_info(FILE *stream, struct instruction *insn, int depth,
void disas_print_insn(FILE *stream, struct disas_context *dctx,
struct instruction *insn, int depth,
const char *format, ...);
+char *disas_alt_name(struct alternative *alt);
#else /* DISAS */
--
2.43.5
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