This allows consumers to specify an opt-in set of features
they want to use in BTF encoding.
Supported features are
encode_force Ignore invalid symbols when encoding BTF.
var Encode variables using BTF_KIND_VAR in BTF.
float Encode floating-point types in BTF.
decl_tag Encode declaration tags using BTF_KIND_DECL_TAG.
type_tag Encode type tags using BTF_KIND_TYPE_TAG.
enum64 Encode enum64 values with BTF_KIND_ENUM64.
optimized Encode representations of optimized functions
with suffixes like ".isra.0" etc
consistent Avoid encoding inconsistent static functions.
These occur when a parameter is optimized out
in some CUs and not others, or when the same
function name has inconsistent BTF descriptions
in different CUs.
Specifying "--btf_features=all" is the equivalent to setting
all of the above. If pahole does not know about a feature
it silently ignores it. These properties allow us to use
the --btf_features option in the kernel pahole_flags.sh
script to specify the desired set of features. If a new
feature is not present in pahole but requested, pahole
BTF encoding will not complain (but will not encode the
feature).
Suggested-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
man-pages/pahole.1 | 20 +++++++++++
pahole.c | 87 +++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 106 insertions(+), 1 deletion(-)
diff --git a/man-pages/pahole.1 b/man-pages/pahole.1
index c1b48de..7c072dc 100644
--- a/man-pages/pahole.1
+++ b/man-pages/pahole.1
@@ -273,6 +273,26 @@ Generate BTF for functions with optimization-related suffixes (.isra, .constprop
.B \-\-btf_gen_all
Allow using all the BTF features supported by pahole.
+.TP
+.B \-\-btf_features=FEATURE_LIST
+Encode BTF using the specified feature list, or specify 'all' for all features supported. This single parameter value can be used as an alternative to unsing multiple BTF-related options. Supported features are
+
+.nf
+ encode_force Ignore invalid symbols when encoding BTF.
+ var Encode variables using BTF_KIND_VAR in BTF.
+ float Encode floating-point types in BTF.
+ decl_tag Encode declaration tags using BTF_KIND_DECL_TAG.
+ type_tag Encode type tags using BTF_KIND_TYPE_TAG.
+ enum64 Encode enum64 values with BTF_KIND_ENUM64.
+ optimized Encode representations of optimized functions
+ with suffixes like ".isra.0" etc
+ consistent Avoid encoding inconsistent static functions.
+ These occur when a parameter is optimized out
+ in some CUs and not others, or when the same
+ function name has inconsistent BTF descriptions
+ in different CUs.
+.fi
+
.TP
.B \-l, \-\-show_first_biggest_size_base_type_member
Show first biggest size base_type member.
diff --git a/pahole.c b/pahole.c
index 7a41dc3..4f00b08 100644
--- a/pahole.c
+++ b/pahole.c
@@ -1229,6 +1229,83 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
#define ARGP_skip_emitting_atomic_typedefs 338
#define ARGP_btf_gen_optimized 339
#define ARGP_skip_encoding_btf_inconsistent_proto 340
+#define ARGP_btf_features 341
+
+/* --btf_features=feature1[,feature2,..] option allows us to specify
+ * opt-in features (or "all"); these are translated into conf_load
+ * values by specifying the associated bool offset and whether it
+ * is a skip option or not; btf_features is for opting _into_ features
+ * so for skip options we have to reverse the logic. For example
+ * "--skip_encoding_btf_type_tag --btf_gen_floats" translate to
+ * "--btf_features=type_tag,float"
+ */
+#define BTF_FEATURE(name, alias, skip) \
+ { #name, #alias, offsetof(struct conf_load, alias), skip }
+
+struct btf_feature {
+ const char *name;
+ const char *option_alias;
+ size_t conf_load_offset;
+ bool skip;
+} btf_features[] = {
+ BTF_FEATURE(encode_force, btf_encode_force, false),
+ BTF_FEATURE(var, skip_encoding_btf_vars, true),
+ BTF_FEATURE(float, btf_gen_floats, false),
+ BTF_FEATURE(decl_tag, skip_encoding_btf_decl_tag, true),
+ BTF_FEATURE(type_tag, skip_encoding_btf_type_tag, true),
+ BTF_FEATURE(enum64, skip_encoding_btf_enum64, true),
+ BTF_FEATURE(optimized, btf_gen_optimized, false),
+ /* the "skip" in skip_encoding_btf_inconsistent_proto is misleading
+ * here; this is a positive feature to ensure consistency of
+ * representation rather than a negative option which we want
+ * to invert. So as a result, "skip" is false here.
+ */
+ BTF_FEATURE(consistent, skip_encoding_btf_inconsistent_proto, false),
+};
+
+#define BTF_MAX_FEATURES 32
+#define BTF_MAX_FEATURE_STR 256
+
+/* Translate --btf_features=feature1[,feature2] into conf_load values.
+ * Explicitly ignores unrecognized features to allow future specification
+ * of new opt-in features.
+ */
+static void parse_btf_features(const char *features, struct conf_load *conf_load)
+{
+ char *feature_list[BTF_MAX_FEATURES] = {};
+ char f[BTF_MAX_FEATURE_STR];
+ bool encode_all = false;
+ int i, j, n = 0;
+
+ strncpy(f, features, sizeof(f));
+
+ if (strcmp(features, "all") == 0) {
+ encode_all = true;
+ } else {
+ char *saveptr = NULL, *s = f, *t;
+
+ while ((t = strtok_r(s, ",", &saveptr)) != NULL) {
+ s = NULL;
+ feature_list[n++] = t;
+ }
+ }
+
+ for (i = 0; i < ARRAY_SIZE(btf_features); i++) {
+ bool *bval = (bool *)(((void *)conf_load) + btf_features[i].conf_load_offset);
+ bool match = encode_all;
+
+ if (!match) {
+ for (j = 0; j < n; j++) {
+ if (strcmp(feature_list[j], btf_features[i].name) == 0) {
+ match = true;
+ break;
+ }
+ }
+ }
+ if (match)
+ *bval = btf_features[i].skip ? false : true;
+ }
+}
static const struct argp_option pahole__options[] = {
{
@@ -1651,6 +1728,12 @@ static const struct argp_option pahole__options[] = {
.key = ARGP_skip_encoding_btf_inconsistent_proto,
.doc = "Skip functions that have multiple inconsistent function prototypes sharing the same name, or that use unexpected registers for parameter values."
},
+ {
+ .name = "btf_features",
+ .key = ARGP_btf_features,
+ .arg = "FEATURE_LIST",
+ .doc = "Specify supported BTF features in FEATURE_LIST or 'all' for all supported features. See the pahole manual page for the list of supported features."
+ },
{
.name = NULL,
}
@@ -1796,7 +1879,7 @@ static error_t pahole__options_parser(int key, char *arg,
case ARGP_btf_gen_floats:
conf_load.btf_gen_floats = true; break;
case ARGP_btf_gen_all:
- conf_load.btf_gen_floats = true; break;
+ parse_btf_features("all", &conf_load); break;
case ARGP_with_flexible_array:
show_with_flexible_array = true; break;
case ARGP_prettify_input_filename:
@@ -1826,6 +1909,8 @@ static error_t pahole__options_parser(int key, char *arg,
conf_load.btf_gen_optimized = true; break;
case ARGP_skip_encoding_btf_inconsistent_proto:
conf_load.skip_encoding_btf_inconsistent_proto = true; break;
+ case ARGP_btf_features:
+ parse_btf_features(arg, &conf_load); break;
default:
return ARGP_ERR_UNKNOWN;
}
--
2.31.1
