[PATCH 01/12] core: Allow asking for a reproducible build

[Arnaldo Carvalho de Melo <acme@kernel.org>]

From: Arnaldo Carvalho de Melo <acme@redhat.com>

This is initially about BTF encoding, we want to load DWARF and encode
BTF from it in a way that is reproducible, i.e. no matter how many
threads we use for the loading/encoding process, the output will be the
same, i.e. the BTF ids produced will be the same for all builds.

This first path just adds the conf_load field and allows it to be asked
for with the '--reproducible_build' option in pahole.

At some point we'll use with --btf_features=+reproducible_build or
'--btf_features=default --btf_features=reproducible_build' to keep the
default set of BTF features and be able to use this in the Linux kernel
build system without doing an extra pahole version check for the
availability of --reproducible_build with pahole versions that already
support --btf_features and thus would ignore "reproducible_build".

Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Kui-Feng Lee <kuifeng@fb.com>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 dwarves.h | 1 +
 pahole.c  | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/dwarves.h b/dwarves.h
index 2393a6c3dc836f39..4dfaa01a00f782d9 100644
--- a/dwarves.h
+++ b/dwarves.h
@@ -87,6 +87,7 @@ struct conf_load {
 	bool			skip_encoding_btf_vars;
 	bool			btf_gen_floats;
 	bool			btf_encode_force;
+	bool			reproducible_build;
 	uint8_t			hashtable_bits;
 	uint8_t			max_hashtable_bits;
 	uint16_t		kabi_prefix_len;
diff --git a/pahole.c b/pahole.c
index 0b9c2de74f146a4d..96e153432fa212a5 100644
--- a/pahole.c
+++ b/pahole.c
@@ -1235,6 +1235,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
 #define ARGP_supported_btf_features 342
 #define ARGP_btf_features_strict 343
 #define ARGP_contains_enumerator 344
+#define ARGP_reproducible_build 345
 
 /* --btf_features=feature1[,feature2,..] allows us to specify
  * a list of requested BTF features or "all" to enable all features.
@@ -1819,6 +1820,11 @@ static const struct argp_option pahole__options[] = {
 		.arg = "FEATURE_LIST_STRICT",
 		.doc = "Specify supported BTF features in FEATURE_LIST_STRICT or 'all' for all supported features.  Unlike --btf_features, unrecognized features will trigger an error."
 	},
+	{
+		.name = "reproducible_build",
+		.key = ARGP_reproducible_build,
+		.doc = "Generate reproducile BTF output"
+	},
 	{
 		.name = NULL,
 	}
@@ -1997,6 +2003,8 @@ 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_reproducible_build:
+		conf_load.reproducible_build = true;	break;
 	case ARGP_btf_features:
 		parse_btf_features(arg, false);		break;
 	case ARGP_supported_btf_features:
-- 
2.44.0