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    SubjectRe: [PATCH v0 07/71] perf tools: Record whether a dso is 64-bit
    On 12/11/13, 5:36 AM, Alexander Shishkin wrote:
    > diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
    > index a0c7c59..80817ec 100644
    > --- a/tools/perf/util/dso.c
    > +++ b/tools/perf/util/dso.c
    > @@ -446,6 +446,7 @@ struct dso *dso__new(const char *name)
    > dso->cache = RB_ROOT;
    > dso->symtab_type = DSO_BINARY_TYPE__NOT_FOUND;
    > dso->data_type = DSO_BINARY_TYPE__NOT_FOUND;
    > + dso->is_64_bit = (sizeof(void *) == 8);
    > dso->loaded = 0;
    > dso->rel = 0;
    > dso->sorted_by_name = 0;
    > diff --git a/tools/perf/util/dso.h b/tools/perf/util/dso.h
    > index 384f2d9..62680e1 100644
    > --- a/tools/perf/util/dso.h
    > +++ b/tools/perf/util/dso.h
    > @@ -91,6 +91,7 @@ struct dso {
    > u8 annotate_warned:1;
    > u8 sname_alloc:1;
    > u8 lname_alloc:1;
    > + u8 is_64_bit:1;
    > u8 sorted_by_name;
    > u8 loaded;
    > u8 rel;
    > diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
    > index eed0b96..a0fc81b 100644
    > --- a/tools/perf/util/symbol-elf.c
    > +++ b/tools/perf/util/symbol-elf.c
    > @@ -595,6 +595,8 @@ int symsrc__init(struct symsrc *ss, struct dso *dso, const char *name,
    > goto out_elf_end;
    > }
    >
    > + ss->is_64_bit = (gelf_getclass(elf) == ELFCLASS64);
    > +
    > ss->symtab = elf_section_by_name(elf, &ehdr, &ss->symshdr, ".symtab",
    > NULL);
    > if (ss->symshdr.sh_type != SHT_SYMTAB)
    > @@ -694,6 +696,7 @@ int dso__load_sym(struct dso *dso, struct map *map,
    > bool remap_kernel = false, adjust_kernel_syms = false;
    >
    > dso->symtab_type = syms_ss->type;
    > + dso->is_64_bit = syms_ss->is_64_bit;
    > dso->rel = syms_ss->ehdr.e_type == ET_REL;
    >
    > /*
    > diff --git a/tools/perf/util/symbol-minimal.c b/tools/perf/util/symbol-minimal.c
    > index ac7070a..b9d1119 100644
    > --- a/tools/perf/util/symbol-minimal.c
    > +++ b/tools/perf/util/symbol-minimal.c
    > @@ -1,3 +1,4 @@
    > +#include "util.h"
    > #include "symbol.h"
    >
    > #include <stdio.h>
    > @@ -287,6 +288,23 @@ int dso__synthesize_plt_symbols(struct dso *dso __maybe_unused,
    > return 0;
    > }
    >
    > +static int fd__is_64_bit(int fd)
    > +{
    > + u8 e_ident[EI_NIDENT];
    > +
    > + if (lseek(fd, 0, SEEK_SET))
    > + return -1;
    > +
    > + if (readn(fd, e_ident, sizeof(e_ident)) != sizeof(e_ident))
    > + return -1;
    > +
    > + if (memcmp(e_ident, ELFMAG, SELFMAG) ||
    > + e_ident[EI_VERSION] != EV_CURRENT)
    > + return -1;
    > +
    > + return e_ident[EI_CLASS] == ELFCLASS64;
    > +}
    > +
    > int dso__load_sym(struct dso *dso, struct map *map __maybe_unused,
    > struct symsrc *ss,
    > struct symsrc *runtime_ss __maybe_unused,
    > @@ -294,6 +312,11 @@ int dso__load_sym(struct dso *dso, struct map *map __maybe_unused,
    > int kmodule __maybe_unused)
    > {
    > unsigned char *build_id[BUILD_ID_SIZE];
    > + int ret;
    > +
    > + ret = fd__is_64_bit(ss->fd);
    > + if (ret >= 0)
    > + dso->is_64_bit = ret;
    >
    > if (filename__read_build_id(ss->name, build_id, BUILD_ID_SIZE) > 0) {
    > dso__set_build_id(dso, build_id);


    Here's what is wrong with this API: you are determining DSO bitness at
    symbol load time, not when the DSO is created and added to the maps.

    As I pointed out in a prior comment you are initializing dso->is_64_bit
    to perf's bitness when the dso object is created (dso__new) but the
    value is not correctly set until dso__load time. Some tools (perf-trace)
    never load symbols, so that value is always wrong in the sense that its
    value has no correlation to the dso object.

    David


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