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    SubjectRe: [PATCH 34/48] perf dwarf-aux: Add die_collect_vars()
    On Wed, 11 Oct 2023 20:50:57 -0700
    Namhyung Kim <namhyung@kernel.org> wrote:

    > The die_collect_vars() is to find all variable information in the scope
    > including function parameters. The struct die_var_type is to save the
    > type of the variable with the location (reg and offset) as well as where
    > it's defined in the code (addr).
    >

    This looks good to me.

    Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

    BTW, I did similar thing in collect_variables_cb()@probe-finder.c, maybe
    this can simplify that too.

    Thank you,

    > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
    > ---
    > tools/perf/util/dwarf-aux.c | 60 +++++++++++++++++++++++++++++++++++++
    > tools/perf/util/dwarf-aux.h | 17 +++++++++++
    > 2 files changed, 77 insertions(+)
    >
    > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
    > index 093d7e82b333..16e63d8caf83 100644
    > --- a/tools/perf/util/dwarf-aux.c
    > +++ b/tools/perf/util/dwarf-aux.c
    > @@ -1545,6 +1545,66 @@ int die_get_cfa(Dwarf *dwarf, u64 pc, int *preg, int *poffset)
    > return -1;
    > }
    >
    > +static int __die_collect_vars_cb(Dwarf_Die *die_mem, void *arg)
    > +{
    > + struct die_var_type **var_types = arg;
    > + Dwarf_Die type_die;
    > + int tag = dwarf_tag(die_mem);
    > + Dwarf_Attribute attr;
    > + Dwarf_Addr base, start, end;
    > + Dwarf_Op *ops;
    > + size_t nops;
    > + struct die_var_type *vt;
    > +
    > + if (tag != DW_TAG_variable && tag != DW_TAG_formal_parameter)
    > + return DIE_FIND_CB_SIBLING;
    > +
    > + if (dwarf_attr(die_mem, DW_AT_location, &attr) == NULL)
    > + return DIE_FIND_CB_SIBLING;
    > +
    > + /*
    > + * Only collect the first location as it can reconstruct the
    > + * remaining state by following the instructions.
    > + * start = 0 means it covers the whole range.
    > + */
    > + if (dwarf_getlocations(&attr, 0, &base, &start, &end, &ops, &nops) <= 0)
    > + return DIE_FIND_CB_SIBLING;
    > +
    > + if (die_get_real_type(die_mem, &type_die) == NULL)
    > + return DIE_FIND_CB_SIBLING;
    > +
    > + vt = malloc(sizeof(*vt));
    > + if (vt == NULL)
    > + return DIE_FIND_CB_END;
    > +
    > + vt->die_off = dwarf_dieoffset(&type_die);
    > + vt->addr = start;
    > + vt->reg = reg_from_dwarf_op(ops);
    > + vt->offset = offset_from_dwarf_op(ops);
    > + vt->next = *var_types;
    > + *var_types = vt;
    > +
    > + return DIE_FIND_CB_SIBLING;
    > +}
    > +
    > +/**
    > + * die_collect_vars - Save all variables and parameters
    > + * @sc_die: a scope DIE
    > + * @var_types: a pointer to save the resulting list
    > + *
    > + * Save all variables and parameters in the @sc_die and save them to @var_types.
    > + * The @var_types is a singly-linked list containing type and location info.
    > + * Actual type can be retrieved using dwarf_offdie() with 'die_off' later.
    > + *
    > + * Callers should free @var_types.
    > + */
    > +void die_collect_vars(Dwarf_Die *sc_die, struct die_var_type **var_types)
    > +{
    > + Dwarf_Die die_mem;
    > +
    > + die_find_child(sc_die, __die_collect_vars_cb, (void *)var_types, &die_mem);
    > +}
    > +
    > #endif
    >
    > /*
    > diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
    > index dc7e98678216..d0ef41738abd 100644
    > --- a/tools/perf/util/dwarf-aux.h
    > +++ b/tools/perf/util/dwarf-aux.h
    > @@ -135,6 +135,15 @@ void die_skip_prologue(Dwarf_Die *sp_die, Dwarf_Die *cu_die,
    > /* Get the list of including scopes */
    > int die_get_scopes(Dwarf_Die *cu_die, Dwarf_Addr pc, Dwarf_Die **scopes);
    >
    > +/* Variable type information */
    > +struct die_var_type {
    > + struct die_var_type *next;
    > + u64 die_off;
    > + u64 addr;
    > + int reg;
    > + int offset;
    > +};
    > +
    > #ifdef HAVE_DWARF_GETLOCATIONS_SUPPORT
    >
    > /* Get byte offset range of given variable DIE */
    > @@ -153,6 +162,9 @@ Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr pc,
    > /* Get the frame base information from CFA */
    > int die_get_cfa(Dwarf *dwarf, u64 pc, int *preg, int *poffset);
    >
    > +/* Save all variables and parameters in this scope */
    > +void die_collect_vars(Dwarf_Die *sc_die, struct die_var_type **var_types);
    > +
    > #else /* HAVE_DWARF_GETLOCATIONS_SUPPORT */
    >
    > static inline int die_get_var_range(Dwarf_Die *sp_die __maybe_unused,
    > @@ -187,6 +199,11 @@ static inline int die_get_cfa(Dwarf *dwarf __maybe_unused, u64 pc __maybe_unused
    > return -1;
    > }
    >
    > +static inline void die_collect_vars(Dwarf_Die *sc_die __maybe_unused,
    > + struct die_var_type **var_types __maybe_unused)
    > +{
    > +}
    > +
    > #endif /* HAVE_DWARF_GETLOCATIONS_SUPPORT */
    >
    > #endif /* _DWARF_AUX_H */
    > --
    > 2.42.0.655.g421f12c284-goog
    >


    --
    Masami Hiramatsu (Google) <mhiramat@kernel.org>

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