From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 728BA5E08C; Wed, 28 Feb 2024 19:39:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709149165; cv=none; b=T/qc6Wj/dBqZq+Ehs1pRmAKqCNPuBwcDKUtad5l44GSF3nittbX5CrjXGRli5EvYsUbUzvXIV4f0lZLmaHEQpTTFwlz2tQBhPQVQs6vId6/NcTIbYP7oY+KFaexJ1T7L7NQCd/LF5+abZP42rHsN/ZLzdmo8RUOnZW4ghIU7pwM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709149165; c=relaxed/simple; bh=gFHujCPhXxiKRFVHgKtx1CZM8LTurcNBRJLLjFO5tro=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=EKNYEGh9Sze/hFVvsjLKReBuUlTZ4iCId6R/uWpFS5J/a+LhG0oRmKA9mucyplaH9/5rNLr+L0sstdC8XOWdkWbDrmLn9tnceEoUzyf9jxRWkD0f3X8XBpN2dNNspWEjyX9VRmKCSyRdF8mf3o0uS9GBZOC5VZBd4YnMTtVQ3EQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JJjVfSii; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JJjVfSii" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9DA20C433F1; Wed, 28 Feb 2024 19:39:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1709149165; bh=gFHujCPhXxiKRFVHgKtx1CZM8LTurcNBRJLLjFO5tro=; h=Date:From:To:Cc:Subject:From; b=JJjVfSiiEwXxcn1BwJ/l6j32/p53Yb5rJKllPhc6i1rXgHPREu0NZAPMWNmxgrbHN wf1E0qX7PIFErQGr0CkPS9PygeNtGKdCt4pbA5NwdIoDm4We7N9vhjPq1JLx/uQpdV EZU6coEAxmr1GkBbl+OBVVpnNhSuJV7XJbmMphcGoL6rYy2BChnX1d3jD5QDVWwoz/ 0WWNNQDM61QH2ibJ5GBnFyRr+zTsxxy2PnwMOPWDywJ7Vp3fI7coi/eMdtMNgBCU/X h16sD+UMqdTRq+rnlH+Q+4ni4Bqld6uxQgkNgYPgRwqBi7fXQ/mZpdSCSdesY9SLT4 6EaAPLl/DoCxw== Date: Wed, 28 Feb 2024 16:39:21 -0300 From: Arnaldo Carvalho de Melo To: dwarves@vger.kernel.org Cc: Linux Kernel Mailing List , bpf@vger.kernel.org, Alan Maguire , Andrii Nakryiko , Jiri Olsa , Jan Engelhardt , Domenico Andreoli , Matthias Schwarzott , Viktor Malik , Eduard Zingerman , J B Subject: ANNOUNCE: pahole v1.26 (more holes, --bpf_features, --contains_enum) Message-ID: Precedence: bulk X-Mailing-List: dwarves@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Url: http://acmel.wordpress.com Message-ID: <20240228193921.JWQp1Mc2M47ffhgIjnHKh8538u4uztVKuznlck9Pk9E@z> Hi, The v1.26 release of pahole and its friends is out, showing more holes (the ones in contained types) the ability to express the BTF features to encode, to simplify the addition of new BTF features in the Linux kernel build infrastructure, a way to find the enumeration with some enumerator and various fixes. Main git repo: git://git.kernel.org/pub/scm/devel/pahole/pahole.git Mirror git repo: https://github.com/acmel/dwarves.git tarball + gpg signature: https://fedorapeople.org/~acme/dwarves/dwarves-1.26.tar.xz https://fedorapeople.org/~acme/dwarves/dwarves-1.26.tar.bz2 https://fedorapeople.org/~acme/dwarves/dwarves-1.26.tar.sign Thanks a lot to all the contributors and distro packagers, you're on the CC list, I appreciate a lot the work you put into these tools, Best Regards, - Arnaldo 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.