| pahole: |
| |
| - When expanding types using 'pahole -E' do it for union and struct typedefs and for enums too. |
| |
| E.g: that 'state' field in 'struct module': |
| |
| $ pahole module | head |
| struct module { |
| enum module_state state; /* 0 4 */ |
| |
| /* XXX 4 bytes hole, try to pack */ |
| |
| struct list_head list; /* 8 16 */ |
| char name[56]; /* 24 56 */ |
| /* --- cacheline 1 boundary (64 bytes) was 16 bytes ago --- */ |
| struct module_kobject mkobj; /* 80 96 */ |
| /* --- cacheline 2 boundary (128 bytes) was 48 bytes ago --- */ |
| $ |
| |
| now gets expanded: |
| |
| $ pahole -E module | head |
| struct module { |
| enum module_state { |
| MODULE_STATE_LIVE = 0, |
| MODULE_STATE_COMING = 1, |
| MODULE_STATE_GOING = 2, |
| MODULE_STATE_UNFORMED = 3, |
| } state; /* 0 4 */ |
| |
| /* XXX 4 bytes hole, try to pack */ |
| |
| $ |
| |
| - Print number of holes, bit holes and bit paddings in class member types. |
| |
| Doing this recursively to show how much waste a complex data structure has |
| is something that still needs to be done, there were the low hanging fruits |
| on the path to having that feature. |
| |
| For instance, for 'struct task_struct' in the Linux kernel we get this |
| extra info: |
| |
| --- task_struct.before.c 2024-02-09 11:38:39.249638750 -0300 |
| +++ task_struct.after.c 2024-02-09 16:19:34.221134835 -0300 |
| @@ -29,6 +29,12 @@ |
| |
| /* --- cacheline 2 boundary (128 bytes) --- */ |
| struct sched_entity se; /* 128 256 */ |
| + |
| + /* XXX last struct has 3 holes */ |
| + |
| /* --- cacheline 6 boundary (384 bytes) --- */ |
| struct sched_rt_entity rt; /* 384 48 */ |
| struct sched_dl_entity dl; /* 432 224 */ |
| + |
| + /* XXX last struct has 1 bit hole */ |
| + |
| /* --- cacheline 10 boundary (640 bytes) was 16 bytes ago --- */ |
| const struct sched_class * sched_class; /* 656 8 */ |
| struct rb_node core_node; /* 664 24 */ |
| @@ -100,6 +103,9 @@ |
| /* --- cacheline 35 boundary (2240 bytes) was 16 bytes ago --- */ |
| struct list_head tasks; /* 2256 16 */ |
| struct plist_node pushable_tasks; /* 2272 40 */ |
| + |
| + /* XXX last struct has 1 hole */ |
| + |
| /* --- cacheline 36 boundary (2304 bytes) was 8 bytes ago --- */ |
| struct rb_node pushable_dl_tasks; /* 2312 24 */ |
| struct mm_struct * mm; /* 2336 8 */ |
| @@ -172,6 +178,9 @@ |
| /* XXX last struct has 4 bytes of padding */ |
| |
| struct vtime vtime; /* 2744 48 */ |
| + |
| + /* XXX last struct has 1 hole */ |
| + |
| /* --- cacheline 43 boundary (2752 bytes) was 40 bytes ago --- */ |
| atomic_t tick_dep_mask; /* 2792 4 */ |
| |
| @@ -396,9 +405,12 @@ |
| /* --- cacheline 145 boundary (9280 bytes) --- */ |
| struct thread_struct thread __attribute__((__aligned__(64))); /* 9280 4416 */ |
| |
| + /* XXX last struct has 1 hole, 1 bit hole */ |
| + |
| /* size: 13696, cachelines: 214, members: 262 */ |
| /* sum members: 13518, holes: 21, sum holes: 162 */ |
| /* sum bitfield members: 82 bits, bit holes: 2, sum bit holes: 46 bits */ |
| /* member types with holes: 4, total: 6, bit holes: 2, total: 2 */ |
| /* paddings: 6, sum paddings: 49 */ |
| /* forced alignments: 2, forced holes: 2, sum forced holes: 88 */ |
| }; |
| |
| - Introduce --contains_enumerator=ENUMERATOR_NAME: |
| |
| E.g.: |
| |
| $ pahole --contains_enumerator S_VERSION |
| enum file_time_flags { |
| S_ATIME = 1, |
| S_MTIME = 2, |
| S_CTIME = 4, |
| S_VERSION = 8, |
| } |
| $ |
| |
| The shorter form --contains_enum is also accepted. |
| |
| - Fix pretty printing when using DWARF, where sometimes the class (-C) and a specified "type_enum", |
| may not be present on the same CU, so wait till both are found. |
| |
| Now this example that reads the 'struct perf_event_header' and 'enum perf_event_type' |
| from the DWARF info in ~/bin/perf to pretty print records in the perf.data file works |
| just like when using type info from BTF in ~/bin/perf: |
| |
| $ pahole -F dwarf -V ~/bin/perf \ |
| --header=perf_file_header \ |
| --seek_bytes '$header.data.offset' \ |
| --size_bytes='$header.data.size' \ |
| -C 'perf_event_header(sizeof,type,type_enum=perf_event_type,filter=type==PERF_RECORD_MMAP2)' \ |
| --prettify perf.data --count 1 |
| pahole: sizeof_operator for 'perf_event_header' is 'size' |
| pahole: type member for 'perf_event_header' is 'type' |
| pahole: type enum for 'perf_event_header' is 'perf_event_type' |
| pahole: filter for 'perf_event_header' is 'type==PERF_RECORD_MMAP2' |
| pahole: seek bytes evaluated from --seek_bytes=$header.data.offset is 0x3f0 |
| pahole: size bytes evaluated from --size_bytes=$header.data.size is 0xd10 |
| // type=perf_event_header, offset=0xc20, sizeof=8, real_sizeof=112 |
| { |
| .header = { |
| .type = PERF_RECORD_MMAP2, |
| .misc = 2, |
| .size = 112, |
| }, |
| .pid = 1533617, |
| .tid = 1533617, |
| .start = 94667542700032, |
| .len = 90112, |
| .pgoff = 16384,{ |
| .maj = 0, |
| .min = 33, |
| .ino = 35914923, |
| .ino_generation = 26870, |
| },{ |
| .build_id_size = 0, |
| .__reserved_1 = 0, |
| .__reserved_2 = 0, |
| .build_id = { 33, 0, 0, 0, -85, 4, 36, 2, 0, 0, 0, 0, -10, 104, 0, 0, 0, 0, 0, 0 }, |
| }, |
| .prot = 5, |
| .flags = 2, |
| .filename = "/usr/bin/ls", |
| }, |
| $ |
| |
| DWARF loader: |
| |
| - Add support for DW_TAG_constant, first seen in Go DWARF. |
| |
| - Fix loading DW_TAG_subroutine_type generated by the Go compiler, where it may |
| have a DW_AT_byte_size. Go DWARF. And pretty print it as if |
| it was from C, this helped in writing BPF programs to attach to Go binaries, using |
| uprobes. |
| |
| BTF loader: |
| |
| - Fix loading of 32-bit signed enums. |
| |
| BTF encoder: |
| |
| - Add 'pahole --btf_features' to allow consumers to specify an opt-in set of |
| features they want to use in BTF encoding. |
| |
| Supported features are a comma-separated combination of |
| |
| 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_func Encode representations of optimized functions |
| with suffixes like ".isra.0" etc |
| consistent_func 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 specified in |
| --btf_features it silently ignores it. |
| |
| The --btf_features can either be specified via a single comma-separated |
| list |
| --btf_features=enum64,float |
| |
| ...or via multiple --btf_features values |
| |
| --btf_features=enum64 --btf_features=float |
| |
| These properties allow us to use the --btf_features option in the kernel |
| scripts/pahole_flags.sh script to specify the desired set of BTF |
| features. |
| |
| If a feature named in --btf_features is not present in the version of |
| pahole used, BTF encoding will not complain. This is desired because it |
| means we no longer have to tie new features to a specific pahole |
| version. |
| |
| Use --btf_features_strict to change that behaviour and bail out if one of |
| the requested features isn't present. |
| |
| To see the supported features, use: |
| |
| $ pahole --supported_btf_features |
| encode_force,var,float,decl_tag,type_tag,enum64,optimized_func,consistent_func |
| $ |
| |
| btfdiff: |
| |
| - Parallelize loading BTF and DWARF, speeding up a bit. |
| |
| - Do type expansion to cover "private" types and enumerations. |
| |
| Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> |
