v1.12 August 2018

- Add a BTF encoder (Martin KaFai Lau)

	BTF (BPF Type Format) is the meta data format which describes
the data types of BPF program/map.  Hence, it basically focus on the C
programming language which the modern BPF is primary using.  The first
use case is to provide a generic pretty print capability for a BPF map.

	BTF has its root from CTF (Compact C-Type format).

- Add Documentation on how to use the BTF encoder: (Arnaldo Carvalho de Melo)

	Using the Linux 'perf' tools integration with BPF/llvm/clang to
show how to generate an object file that then gets its DWARF info used
to create a .BTF ELF section with this new BTF format. That augmented
eBPF ELF object file is then loaded while 'perf ftrace -g *bpf*' is used
to show the kernel BTF validation process.

- Initial support for DW_TAG_partial_unit (Arnaldo Carvalho de Melo)

	Just by treating these sections as DW_TAG_compile_unit, which is
enough for the structs that don't contain cross-section type references
to be correctly loaded and pretty-printed with pahole.

	This doesn't affect the kernel or modules, where such DWARF
compression techniques are not used so far. (Arnaldo Carvalho de Melo)

- Print cacheline boundaries in multiple union members, (Arnaldo Carvalho de Melo)

	We were showing it just on the first inner union member members,
as if it was a struct, now we restart the cacheline boundaries when
moving to print the next inner struct.

	As an example, look at 'struct audit_context' where the only
cacheline boundary printed for the following unnamed union was the first
one, for the 'socketcall' struct member, now that cacheline boundary
appears in each of the union member inner structs:

    struct audit_context {
    <SNIP>
            union {
                    struct {
                            int        nargs;                /*   824     4 */

                            /* XXX 4 bytes hole, try to pack */

                            /* --- cacheline 13 boundary (832 bytes) --- */
                            long int   args[6];              /*   832    48 */
                    } socketcall;                            /*   824    56 */
                    struct {
                            kuid_t     uid;                  /*   824     4 */
                            kgid_t     gid;                  /*   828     4 */
                            /* --- cacheline 13 boundary (832 bytes) --- */
                            umode_t    mode;                 /*   832     2 */

                            /* XXX 2 bytes hole, try to pack */

                            u32        osid;                 /*   836     4 */
                            int        has_perm;             /*   840     4 */
                            uid_t      perm_uid;             /*   844     4 */
                            gid_t      perm_gid;             /*   848     4 */
                            umode_t    perm_mode;            /*   852     2 */

                            /* XXX 2 bytes hole, try to pack */

                            long unsigned int qbytes;        /*   856     8 */
                    } ipc;                                   /*   824    40 */
                    struct {
                            mqd_t      mqdes;                /*   824     4 */

                            /* XXX 4 bytes hole, try to pack */

                            /* --- cacheline 13 boundary (832 bytes) --- */
                            struct mq_attr mqstat;           /*   832    64 */
                    } mq_getsetattr;                         /*   824    72 */
                    struct {
                            mqd_t      mqdes;                /*   824     4 */
                            int        sigev_signo;          /*   828     4 */
                    } mq_notify;                             /*   824     8 */
                    struct {
                            mqd_t      mqdes;                /*   824     4 */

                            /* XXX 4 bytes hole, try to pack */

                            /* --- cacheline 13 boundary (832 bytes) --- */
                            size_t     msg_len;              /*   832     8 */
                            unsigned int msg_prio;           /*   840     4 */

                            /* XXX 4 bytes hole, try to pack */

                            struct timespec64 abs_timeout;   /*   848    16 */
                    } mq_sendrecv;                           /*   824    40 */
                    struct {
                            int        oflag;                /*   824     4 */
                            umode_t    mode;                 /*   828     2 */

                            /* XXX 2 bytes hole, try to pack */

                            /* --- cacheline 13 boundary (832 bytes) --- */
                            struct mq_attr attr;             /*   832    64 */
                    } mq_open;                               /*   824    72 */
                    struct {
                            pid_t      pid;                  /*   824     4 */
                            struct audit_cap_data cap;       /*   828    32 */
                    } capset;                                /*   824    36 */
                    struct {
                            int        fd;                   /*   824     4 */
                            int        flags;                /*   828     4 */
                    } mmap;                                  /*   824     8 */
                    struct {
                            int        argc;                 /*   824     4 */
                    } execve;                                /*   824     4 */
                    struct {
                            char *     name;                 /*   824     8 */
                    } module;                                /*   824     8 */
            };                                               /*   824    72 */
            /* --- cacheline 14 boundary (896 bytes) --- */
            int                        fds[2];               /*   896     8 */
            struct audit_proctitle     proctitle;            /*   904    16 */

            /* size: 920, cachelines: 15, members: 46 */
            /* sum members: 912, holes: 2, sum holes: 8 */
            /* last cacheline: 24 bytes */
    };

- Show where a struct was used, e.g.

      $ pahole -I vmlinux
    <SNIP>
      /* Used at: /home/acme/git/perf/init/main.c */
      /* <1f4a5> /home/acme/git/perf/arch/x86/include/asm/orc_types.h:85 */
      struct orc_entry {
              s16                        sp_offset;            /*     0     2 */
              s16                        bp_offset;            /*     2     2 */
     <SNIP>

- Show offsets at union members (Arnaldo Carvalho de Melo, suggested by Matthew Wilcox):

	In complex structs with multiple complex unions figuring out the
offset for a given union member is difficult, as one needs to figure out
the union, go to the end of it to see the offset.

    This way, for instance, the Linux kernel's 'struct page' shows now as:

    struct page {
            long unsigned int          flags;                /*     0     8 */
            union {
                    struct address_space * mapping;          /*     8     8 */
                    void *             s_mem;                /*     8     8 */
                    atomic_t           compound_mapcount;    /*     8     4 */
            };                                               /*     8     8 */
            union {
                    long unsigned int  index;                /*    16     8 */
                    void *             freelist;             /*    16     8 */
            };                                               /*    16     8 */
            union {
                    long unsigned int  counters;             /*    24     8 */
                    struct {
                            union {
                                    atomic_t _mapcount;      /*    24     4 */
                                    unsigned int active;     /*    24     4 */
                                    struct {
                                            unsigned int inuse:16; /*    24:16  4 */
                                            unsigned int objects:15; /*    24: 1  4 */
                                            unsigned int frozen:1; /*    24: 0  4 */
                                    };                       /*    24     4 */
                                    int units;               /*    24     4 */
                            };                               /*    24     4 */
                            atomic_t   _refcount;            /*    28     4 */
                    };                                       /*    24     8 */
            };                                               /*    24     8 */
            union {
                    struct list_head   lru;                  /*    32    16 */
                    struct dev_pagemap * pgmap;              /*    32     8 */
                    struct {
                            struct page * next;              /*    32     8 */
                            int        pages;                /*    40     4 */
                            int        pobjects;             /*    44     4 */
                    };                                       /*    32    16 */
                    struct callback_head callback_head;      /*    32    16 */
                    struct {
                            long unsigned int compound_head; /*    32     8 */
                            unsigned int compound_dtor;      /*    40     4 */
                            unsigned int compound_order;     /*    44     4 */
                    };                                       /*    32    16 */
                    struct {
                            long unsigned int __pad;         /*    32     8 */
                            pgtable_t  pmd_huge_pte;         /*    40     8 */
                    };                                       /*    32    16 */
            };                                               /*    32    16 */
            union {
                    long unsigned int  private;              /*    48     8 */
                    spinlock_t         ptl;                  /*    48     4 */
                    struct kmem_cache * slab_cache;          /*    48     8 */
            };                                               /*    48     8 */
            struct mem_cgroup *        mem_cgroup;           /*    56     8 */

            /* size: 64, cachelines: 1, members: 7 */
    };

- Search and use running kernel vmlinux when no file is passed (Arnaldo Carvalho de Melo)

	Now it is possible to use it just as:

    $ pahole -C sk_buff_head
    struct sk_buff_head {
            struct sk_buff *           next;                 /*     0     8 */
            struct sk_buff *           prev;                 /*     8     8 */
            __u32                      qlen;                 /*    16     4 */
            spinlock_t                 lock;                 /*    20     4 */

            /* size: 24, cachelines: 1, members: 4 */
            /* last cacheline: 24 bytes */
    };
    $

	This will look at /sys/kernel/notes, find the running kernel
build-id, and then search the usual locations (vmlinux,
/lib/modules/`uname -r`/build/vmlinux, the debuginfo package paths, etc)
to find the matching vmlinux with the DWARF info to use. Build-ids are
now ubiquitous, so this shortens a the most common binary used.

- Document 'pahole --hex' in the man page (Arnaldo Carvalho de Melo)

	This option shows offsets and sizes in hexadecimal, helping to
correlate with reports using that notation.

	E.g.:

    $ pahole --hex -C sk_buff_head
    struct sk_buff_head {
            struct sk_buff *           next;                 /*     0   0x8 */
            struct sk_buff *           prev;                 /*   0x8   0x8 */
            __u32                      qlen;                 /*  0x10   0x4 */
            spinlock_t                 lock;                 /*  0x14   0x4 */

            /* size: 24, cachelines: 1, members: 4 */
            /* last cacheline: 24 bytes */
    };
    $

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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v1.12 - New Release

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
4 files changed