From: Namhyung Kim <namhyung@kernel.org>
To: Zecheng Li <zli94@ncsu.edu>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>,
Adrian Hunter <adrian.hunter@intel.com>,
James Clark <james.clark@linaro.org>,
xliuprof@google.com, linux-perf-users@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 02/11] perf dwarf-aux: Add die_get_pointer_type to get pointer types
Date: Tue, 10 Feb 2026 18:17:32 -0800 [thread overview]
Message-ID: <aYvmvNUcoXpNOBW0@google.com> (raw)
In-Reply-To: <20260127020617.2804780-3-zli94@ncsu.edu>
On Mon, Jan 26, 2026 at 09:04:55PM -0500, Zecheng Li wrote:
> When a variable type is wrapped in typedef/qualifiers, callers may need
> to first resolve it to the underlying DW_TAG_pointer_type or
> DW_TAG_array_type. A simple tag check is not enough and directly calling
> __die_get_real_type() can stop at the pointer type (e.g. typedef ->
> pointer) instead of the pointee type.
>
> Add die_get_pointer_type() helper that follows typedef/qualifier chains
> and returns the underlying pointer DIE. Use it in annotate-data.c so
> pointer checks and dereference work correctly for typedef'd pointers.
>
> Signed-off-by: Zecheng Li <zli94@ncsu.edu>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Thanks,
Namhyung
> ---
> tools/perf/util/annotate-data.c | 39 +++++++++++++++++++--------------
> tools/perf/util/dwarf-aux.c | 27 +++++++++++++++++++++++
> tools/perf/util/dwarf-aux.h | 2 ++
> 3 files changed, 51 insertions(+), 17 deletions(-)
>
> diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
> index 99ffc6d70565..8ff1972981b7 100644
> --- a/tools/perf/util/annotate-data.c
> +++ b/tools/perf/util/annotate-data.c
> @@ -455,13 +455,6 @@ static const char *match_result_str(enum type_match_result tmr)
> }
> }
>
> -static bool is_pointer_type(Dwarf_Die *type_die)
> -{
> - int tag = dwarf_tag(type_die);
> -
> - return tag == DW_TAG_pointer_type || tag == DW_TAG_array_type;
> -}
> -
> static bool is_compound_type(Dwarf_Die *type_die)
> {
> int tag = dwarf_tag(type_die);
> @@ -474,19 +467,24 @@ static bool is_better_type(Dwarf_Die *type_a, Dwarf_Die *type_b)
> {
> Dwarf_Word size_a, size_b;
> Dwarf_Die die_a, die_b;
> + Dwarf_Die ptr_a, ptr_b;
> + Dwarf_Die *ptr_type_a, *ptr_type_b;
> +
> + ptr_type_a = die_get_pointer_type(type_a, &ptr_a);
> + ptr_type_b = die_get_pointer_type(type_b, &ptr_b);
>
> /* pointer type is preferred */
> - if (is_pointer_type(type_a) != is_pointer_type(type_b))
> - return is_pointer_type(type_b);
> + if ((ptr_type_a != NULL) != (ptr_type_b != NULL))
> + return ptr_type_b != NULL;
>
> - if (is_pointer_type(type_b)) {
> + if (ptr_type_b) {
> /*
> * We want to compare the target type, but 'void *' can fail to
> * get the target type.
> */
> - if (die_get_real_type(type_a, &die_a) == NULL)
> + if (die_get_real_type(ptr_type_a, &die_a) == NULL)
> return true;
> - if (die_get_real_type(type_b, &die_b) == NULL)
> + if (die_get_real_type(ptr_type_b, &die_b) == NULL)
> return false;
>
> type_a = &die_a;
> @@ -539,7 +537,7 @@ static enum type_match_result check_variable(struct data_loc_info *dloc,
> * and local variables are accessed directly without a pointer.
> */
> if (needs_pointer) {
> - if (!is_pointer_type(type_die) ||
> + if (die_get_pointer_type(type_die, type_die) == NULL ||
> __die_get_real_type(type_die, type_die) == NULL)
> return PERF_TMR_NO_POINTER;
> }
> @@ -880,12 +878,16 @@ static void update_var_state(struct type_state *state, struct data_loc_info *dlo
> continue;
>
> if (var->reg == DWARF_REG_FB || var->reg == fbreg || var->reg == state->stack_reg) {
> + Dwarf_Die ptr_die;
> + Dwarf_Die *ptr_type;
> int offset = var->offset;
> struct type_state_stack *stack;
>
> + ptr_type = die_get_pointer_type(&mem_die, &ptr_die);
> +
> /* If the reg location holds the pointer value, dereference the type */
> - if (!var->is_reg_var_addr && is_pointer_type(&mem_die) &&
> - __die_get_real_type(&mem_die, &mem_die) == NULL)
> + if (!var->is_reg_var_addr && ptr_type &&
> + __die_get_real_type(ptr_type, &mem_die) == NULL)
> continue;
>
> if (var->reg != DWARF_REG_FB)
> @@ -1110,7 +1112,9 @@ static enum type_match_result check_matching_type(struct type_state *state,
> goto check_non_register;
>
> if (state->regs[reg].kind == TSR_KIND_TYPE) {
> + Dwarf_Die ptr_die;
> Dwarf_Die sized_type;
> + Dwarf_Die *ptr_type;
> struct strbuf sb;
>
> strbuf_init(&sb, 32);
> @@ -1122,7 +1126,8 @@ static enum type_match_result check_matching_type(struct type_state *state,
> * Normal registers should hold a pointer (or array) to
> * dereference a memory location.
> */
> - if (!is_pointer_type(&state->regs[reg].type)) {
> + ptr_type = die_get_pointer_type(&state->regs[reg].type, &ptr_die);
> + if (!ptr_type) {
> if (dloc->op->offset < 0 && reg != state->stack_reg)
> goto check_kernel;
>
> @@ -1130,7 +1135,7 @@ static enum type_match_result check_matching_type(struct type_state *state,
> }
>
> /* Remove the pointer and get the target type */
> - if (__die_get_real_type(&state->regs[reg].type, type_die) == NULL)
> + if (__die_get_real_type(ptr_type, type_die) == NULL)
> return PERF_TMR_NO_POINTER;
>
> dloc->type_offset = dloc->op->offset + state->regs[reg].offset;
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index b57cdc8860f0..96cfcbd40c45 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -303,6 +303,33 @@ Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem)
> return vr_die;
> }
>
> +/**
> + * die_get_pointer_type - Get a pointer/array type die
> + * @type_die: a DIE of a type
> + * @die_mem: where to store a type DIE
> + *
> + * Get a pointer/array type DIE from @type_die. If the type is a typedef or
> + * qualifier (const, volatile, etc.), follow the chain to find the underlying
> + * pointer type.
> + */
> +Dwarf_Die *die_get_pointer_type(Dwarf_Die *type_die, Dwarf_Die *die_mem)
> +{
> + int tag;
> +
> + do {
> + tag = dwarf_tag(type_die);
> + if (tag == DW_TAG_pointer_type || tag == DW_TAG_array_type)
> + return type_die;
> + if (tag != DW_TAG_typedef && tag != DW_TAG_const_type &&
> + tag != DW_TAG_restrict_type && tag != DW_TAG_volatile_type &&
> + tag != DW_TAG_shared_type)
> + return NULL;
> + type_die = die_get_type(type_die, die_mem);
> + } while (type_die);
> +
> + return NULL;
> +}
> +
> /* Get attribute and translate it as a udata */
> static int die_get_attr_udata(Dwarf_Die *tp_die, unsigned int attr_name,
> Dwarf_Word *result)
> diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
> index b3ee5df0b6be..8045281f219c 100644
> --- a/tools/perf/util/dwarf-aux.h
> +++ b/tools/perf/util/dwarf-aux.h
> @@ -60,6 +60,8 @@ Dwarf_Die *die_get_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem);
> Dwarf_Die *__die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem);
> /* Get a type die, but skip qualifiers and typedef */
> Dwarf_Die *die_get_real_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem);
> +/* Get a pointer/array type, following typedefs/qualifiers */
> +Dwarf_Die *die_get_pointer_type(Dwarf_Die *type_die, Dwarf_Die *die_mem);
>
> /* Check whether the DIE is signed or not */
> bool die_is_signed_type(Dwarf_Die *tp_die);
> --
> 2.52.0
>
next prev parent reply other threads:[~2026-02-11 2:17 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-27 2:04 [PATCH v1 00/11] perf tools: Improvements to data type profiler Zecheng Li
2026-01-27 2:04 ` [PATCH v1 01/11] perf dwarf-aux: Skip check_variable for die_find_variable_by_reg Zecheng Li
2026-02-11 2:08 ` Namhyung Kim
2026-01-27 2:04 ` [PATCH v1 02/11] perf dwarf-aux: Add die_get_pointer_type to get pointer types Zecheng Li
2026-02-11 2:17 ` Namhyung Kim [this message]
2026-01-27 2:04 ` [PATCH v1 03/11] perf dwarf-aux: Preserve typedefs in match_var_offset Zecheng Li
2026-02-11 2:23 ` Namhyung Kim
2026-01-27 2:04 ` [PATCH v1 04/11] perf annotate-data: Improve type comparison from different scopes Zecheng Li
2026-02-11 2:25 ` Namhyung Kim
2026-01-27 2:04 ` [PATCH v1 05/11] perf dwarf-aux: Handle array types in die_get_member_type Zecheng Li
2026-01-27 2:04 ` [PATCH v1 06/11] perf annotate-data: Collect global variables without name Zecheng Li
2026-02-11 2:29 ` Namhyung Kim
2026-01-27 2:05 ` [PATCH v1 07/11] perf annotate-data: Handle global variable access with const register Zecheng Li
2026-02-11 2:37 ` Namhyung Kim
2026-01-27 2:05 ` [PATCH v1 08/11] perf annotate-data: Add invalidate_reg_state() helper for x86 Zecheng Li
2026-02-11 2:38 ` Namhyung Kim
2026-01-27 2:05 ` [PATCH v1 09/11] perf annotate-data: Invalidate caller-saved regs for all calls Zecheng Li
2026-01-27 2:05 ` [PATCH v1 10/11] perf annotate-data: Use DWARF location ranges to preserve reg state Zecheng Li
2026-01-27 2:05 ` [PATCH v1 11/11] perf dwarf-aux: Collect all variable locations for insn tracking Zecheng Li
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aYvmvNUcoXpNOBW0@google.com \
--to=namhyung@kernel.org \
--cc=acme@kernel.org \
--cc=adrian.hunter@intel.com \
--cc=alexander.shishkin@linux.intel.com \
--cc=irogers@google.com \
--cc=james.clark@linaro.org \
--cc=jolsa@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=xliuprof@google.com \
--cc=zli94@ncsu.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.