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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@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-28-alexandre.chartre@oracle.com
This commit is contained in:
Alexandre Chartre 2025-11-21 10:53:37 +01:00 committed by Peter Zijlstra
parent 8308fd0019
commit 56967b9a77
1 changed files with 52 additions and 6 deletions
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58
tools/objtool/disas.c
View File

@ -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 int ft_flags)
{
return (ft_flags & ALT_FEATURE_MASK);
}
static int alt_flags(unsigned int 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.
@ -635,7 +651,12 @@ const char *disas_alt_type_name(struct instruction *insn)
*/
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) {
@ -649,13 +670,37 @@ char *disas_alt_name(struct alternative *alt)
case ALT_TYPE_INSTRUCTIONS:
/*
* This is a non-default group alternative. Create a unique
* name using the offset of the first original and alternative
* 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
*/
asprintf(&str, "ALTERNATIVE %lx.%lx",
alt->insn->alt_group->orig_group->first_insn->offset,
alt->insn->alt_group->first_insn->offset);
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;
}
@ -892,6 +937,7 @@ static void *disas_alt(struct disas_context *dctx,
WARN("%s has more alternatives than supported", alt_name);
break;
}
dalt = &dalts[i];
err = disas_alt_init(dalt, orig_insn, alt);
if (err) {