Introduce an option --btf_encode_symbols to pahole so that pahole
will only encode global symbols upon request. On the kernel side,
we can add a Kconfig to turn on this feature. This would make the
rollout of pahole v1.18 safe against potential bugs in the feature
introduced in commit f3d9054ba8ff ("btf_encoder: Teach pahole to
store percpu variables in vmlinux BTF.").
Signed-off-by: Hao Luo <haoluo@xxxxxxxxxx>
---
btf_encoder.c | 5 ++++-
btf_encoder.h | 2 +-
pahole.c | 11 ++++++++++-
3 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/btf_encoder.c b/btf_encoder.c
index 982f59d..54ffdd1 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -237,7 +237,7 @@ static struct variable *hashaddr__find_variable(const struct hlist_head hashtabl
return NULL;
}
-int cu__encode_btf(struct cu *cu, int verbose, bool force)
+int cu__encode_btf(struct cu *cu, int verbose, bool force, bool encode_symbols)
{
bool add_index_type = false;
uint32_t type_id_off;
@@ -314,6 +314,9 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force)
}
}
+ /* if there is no request to encode symbols, just finish. */
+ if (!encode_symbols)
+ goto out;
if (btfe->percpu_shndx == 0 || !btfe->symtab)
goto out;
diff --git a/btf_encoder.h b/btf_encoder.h
index bca2348..f2e95fe 100644
--- a/btf_encoder.h
+++ b/btf_encoder.h
@@ -13,6 +13,6 @@ struct cu;
int btf_encoder__encode();
-int cu__encode_btf(struct cu *cu, int verbose, bool force);
+int cu__encode_btf(struct cu *cu, int verbose, bool force, bool encode_symbols);
#endif /* _BTF_ENCODER_H_ */
diff --git a/pahole.c b/pahole.c
index e1cde61..079d951 100644
--- a/pahole.c
+++ b/pahole.c
@@ -26,6 +26,7 @@
static bool btf_encode;
static bool ctf_encode;
static bool first_obj_only;
+static bool btf_encode_symbols;
static uint8_t class__include_anonymous;
static uint8_t class__include_nested_anonymous;
@@ -809,6 +810,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
#define ARGP_header_type 314
#define ARGP_size_bytes 315
#define ARGP_range 316
+#define ARGP_btf_encode_symbols 317
static const struct argp_option pahole__options[] = {
{
@@ -1087,6 +1089,11 @@ static const struct argp_option pahole__options[] = {
.key = 'J',
.doc = "Encode as BTF",
},
+ {
+ .name = "btf_encode_symbols",
+ .key = ARGP_btf_encode_symbols,
+ .doc = "Encode global symbols in BTF. Off by default."
+ },
{
.name = "force",
.key = 'j',
@@ -1207,6 +1214,8 @@ static error_t pahole__options_parser(int key, char *arg,
conf.range = arg; break;
case ARGP_header_type:
conf.header_type = arg; break;
+ case ARGP_btf_encode_symbols:
+ btf_encode_symbols = true; break;
default:
return ARGP_ERR_UNKNOWN;
}
@@ -2352,7 +2361,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
goto filter_it;
if (btf_encode) {
- cu__encode_btf(cu, global_verbose, force);
+ cu__encode_btf(cu, global_verbose, force, btf_encode_symbols);
return LSK__KEEPIT;
}
--
2.28.0.681.g6f77f65b4e-goog
