To solve problems similar to _RH_KABI_REPLACE. The
_RH_KABI_REPLACE(_orig, _new) macros perserve size alignment and kabi
agreement between _orig and _new.Below is the definition of this macro:
# define _RH_KABI_REPLACE(_orig, _new) \
union { \
_new; \
struct { \
_orig; \
} __UNIQUE_ID(rh_kabi_hide); \
__RH_KABI_CHECK_SIZE_ALIGN(_orig, _new); \
}
__UNIQUE_ID uses the __COUNTER__ macro, and the __COUNTER__ macro is
automatically incremented by 1 every time it is precompiled. Therefore,
in different compilation units, the same structure has different
names.Here is a concrete example:
struct acpi_dev_node {
union {
struct acpi_device *companion;
struct {
void *handle;
} __UNIQUE_ID_rh_kabi_hide29;
union { };
};
};
struct acpi_dev_node {
union {
struct acpi_device *companion;
struct {
void *handle;
} __UNIQUE_ID_rh_kabi_hide31;
union { };
};
};
Finally, it will cause the btf algorithm to de-duplication efficiency is
not high, and time-consuming. For example, running ./pahole -J
vmlinux-3.10.0-1160.el7.x86_64 without --kabi_prefix flag, the running
time is:
real 8m28.912s
user 8m27.271s
sys 0m1.471s
And the size of the generated btf segment is 30678240 bytes.
After adding the patch, running ./pahole
--kabi_prefix=__UNIQUE_ID_rh_kabi_hide -J
vmlinux-3.10.0-1160.el7.x86_64. The running time of the command is:
real 0m19.634s
user 0m18.457s
sys 0m1.169s
And the size of the generated btf segment is 3117719 bytes.
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
Cc: Wenan Mao <wenan.mao@xxxxxxxxxxxxxxxxx>
Signed-off-by: Shuyi Cheng <chengshuyi@xxxxxxxxxxxxxxxxx>
---
v1:
https://lore.kernel.org/dwarves/a249699a-7c6c-4d4a-71b0-87981c8d229e@xxxxxxxxxxxxxxxxx/
v1->v2:
-- Change btf_prefix to --kabi_prefix.
-- Add man page.
-- Add space after if and comma.
v2:
https://lore.kernel.org/dwarves/ec80d351-ac2f-5c48-c339-c2c503d36d68@xxxxxxxxxxxxxxxxx/
v2->v3:
-- Keep the '=' indentation.
-- Remove extra whitespace.
man-pages/pahole.1 | 4 ++++
pahole.c | 10 ++++++++++
pahole_strings.h | 2 ++
strings.c | 9 ++++++++-
4 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/man-pages/pahole.1 b/man-pages/pahole.1
index a10738f..2659fe6 100644
--- a/man-pages/pahole.1
+++ b/man-pages/pahole.1
@@ -340,6 +340,10 @@ Show a traditional string version, i.e.: "v1.18".
Show a numeric only version, suitable for use in Makefiles and scripts
where
one wants to know what if the installed version has some feature,
i.e.: 118 instead of "v1.18".
+.TP
+.B \-\-kabi_prefix=STRING
+When the prefix of the string is STRING, treat the string as STRING.
+
.SH NOTES
To enable the generation of debugging information in the Linux kernel
build
diff --git a/pahole.c b/pahole.c
index dc40ccf..f2406e4 100644
--- a/pahole.c
+++ b/pahole.c
@@ -24,6 +24,7 @@
#include "btf_encoder.h"
#include "libbtf.h"
#include "lib/bpf/src/libbpf.h"
+#include "pahole_strings.h"
static bool btf_encode;
static bool ctf_encode;
@@ -855,6 +856,7 @@ ARGP_PROGRAM_VERSION_HOOK_DEF = dwarves_print_version;
#define ARGP_btf_gen_floats 322
#define ARGP_btf_gen_all 323
#define ARGP_with_flexible_array 324
+#define ARGP_kabi_prefix 325
static const struct argp_option pahole__options[] = {
{
@@ -1140,6 +1142,12 @@ static const struct argp_option pahole__options[] = {
.doc = "Path to the base BTF file",
},
{
+ .name = "kabi_prefix",
+ .key = ARGP_kabi_prefix,
+ .arg = "STRING",
+ .doc = "When the prefix of the string is STRING, treat the string as
STRING.",
+ },
+ {
.name = "btf_encode",
.key = 'J',
.doc = "Encode as BTF",
@@ -1297,6 +1305,8 @@ static error_t pahole__options_parser(int key,
char *arg,
btf_encode_force = true; break;
case ARGP_btf_base:
base_btf_file = arg; break;
+ case ARGP_kabi_prefix:
+ kabi_prefix = arg; break;
case ARGP_numeric_version:
print_numeric_version = true; break;
case ARGP_btf_gen_floats:
diff --git a/pahole_strings.h b/pahole_strings.h
index 522fbf2..a836ba8 100644
--- a/pahole_strings.h
+++ b/pahole_strings.h
@@ -14,6 +14,8 @@ struct strings {
struct btf *btf;
};
+extern const char *kabi_prefix;
+
struct strings *strings__new(void);
void strings__delete(struct strings *strings);
diff --git a/strings.c b/strings.c
index d37f49d..d5eb3a1 100644
--- a/strings.c
+++ b/strings.c
@@ -17,6 +17,8 @@
#include "dutil.h"
#include "lib/bpf/src/libbpf.h"
+const char *kabi_prefix;
+
struct strings *strings__new(void)
{
struct strings *strs = malloc(sizeof(*strs));
@@ -48,7 +50,12 @@ strings_t strings__add(struct strings *strs, const
char *str)
if (str == NULL)
return 0;
- index = btf__add_str(strs->btf, str);
+ if (kabi_prefix &&
+ strncmp(str, kabi_prefix, strlen(kabi_prefix)) == 0)
+ index = btf__add_str(strs->btf, kabi_prefix);
+ else
+ index = btf__add_str(strs->btf, str);
+
if (index < 0)
return 0;
--
1.8.3.1
