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 6C9BD19CC39; Sat, 30 Aug 2025 07:31:05 +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=1756539065; cv=none; b=C62nINBsOCDX1AzBXn7viPJtBJVYNetHkvquXPO+VhhdjcUNCxyTkRvtvhYUTOoBontV2PVzVZFrwiGtwtO+k0qfCENrYaZnmvp77nvuw0np2ywOHnq60sz+gRPVlKJGG3iihBUX3178iQYkiil+nE7iCrG2N7wPQaTJJGfWiHw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756539065; c=relaxed/simple; bh=+Nb4MqxXTKnS1ljG6Gfu0099pT0i+02LE9muMh6CdUU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=O9mkUEuwvDrmU9MeEUlmy3UKz3/zdOYfB/88q12pOl6n4oM3p1pF8lP+zpsnrbTWdb05s0Awcm3d320SZbE4jeg2EbN7m8p21U7PtJb7P9kH7StDCpGpvD23lV1dGwZtb3fh5M+BSMsFQflihQSBo07QwVFPZOzATov71kXTcHc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=thbXXHfx; 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="thbXXHfx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 792EFC4CEEB; Sat, 30 Aug 2025 07:31:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1756539065; bh=+Nb4MqxXTKnS1ljG6Gfu0099pT0i+02LE9muMh6CdUU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=thbXXHfxJVBds/Rpbkj4YEFWNZmpTdcmhli12SCdgHIbz2QYh0LtbwgnqPlxasCN6 CNkpa5acyS+evHJ2S1cPElH8ziFEYdzM+8XIFAT2jw6zFwhGYGjw6xbd0oSYpEovk+ gpNvrCMMIoLfJwz6zYUkh97j2vT6ly8KTRYrh2jIPJXZvuuErH40ciCUm759/3VxAP 8mX5dxbYrCBNOxY8jxh4016vEnw+OQrpaoevXeFpcEhX/GUoRwoMD0RRn/JsDeOND8 z2U28AptpuIYfLhHmKjs3U6cZ8O+M/Ueijv/UIEbAP7o8PS1UfUQQl/wMknGQfnGFK qK9c837yegDhA== Date: Sat, 30 Aug 2025 00:31:03 -0700 From: Namhyung Kim To: Zecheng Li Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , Masami Hiramatsu , Xu Liu , linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 08/10] perf dwarf-aux: Skip check_variable for die_find_variable_by_reg Message-ID: References: <20250825195806.226328-1-zecheng@google.com> Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250825195806.226328-1-zecheng@google.com> On Mon, Aug 25, 2025 at 07:58:06PM +0000, Zecheng Li wrote: > In die_find_variable_by_reg, match_var_offset already performs > sufficient checking and type matching. The additional check_variable > call is redundant, and its need_pointer logic is only a heuristic. Since > DWARF encodes accurate type information, which match_var_offset > verifies, skipping check_variable improves both coverage and accuracy. > > This change implements Looks like you can split these into separate commits. > > - Return type from die_find_variable_by_reg via a new `type` field in > find_var_data. Sounds ok. > > - In match_var_offset, use __die_get_real_type instead of > die_get_real_type to preserve typedefs. Move the (offset == 0) branch Why do you want to preserve typedefs? I think a variable type can be typedef to a pointer then now it won't resolve that target type anymore. > after the is_pointer check to ensure the correct type is used, fixing > cases where an incorrect pointer type was chosen when the access > offset was 0. > > - When comparing types from different scopes, first compare their type > offsets. A larger offset means the field belongs to an outer > (enclosing) struct. This helps resolve cases where a pointer is found > in an inner scope, but a struct containing that pointer exists in an > outer scope. Previously, is_better_type would prefer the pointer type, > but the struct type is actually more complete and should be chosen. Can we improve is_better_type() then? Thanks, Namhyung > > Signed-off-by: Zecheng Li > --- > tools/perf/util/annotate-data.c | 12 ++++++++---- > tools/perf/util/dwarf-aux.c | 30 +++++++++++++++++------------- > tools/perf/util/dwarf-aux.h | 2 +- > 3 files changed, 26 insertions(+), 18 deletions(-) > > diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c > index e067e91f2037..b1a4b02afeb1 100644 > --- a/tools/perf/util/annotate-data.c > +++ b/tools/perf/util/annotate-data.c > @@ -1551,19 +1551,21 @@ static int find_data_type_die(struct data_loc_info *dloc, Dwarf_Die *type_die) > if (!die_find_variable_by_addr(&scopes[i], dloc->var_addr, > &var_die, &type_offset)) > continue; > + /* Found a variable, see if it's correct */ > + result = check_variable(dloc, &var_die, &mem_die, reg, > + type_offset, is_fbreg); > } else { > /* Look up variables/parameters in this scope */ > if (!die_find_variable_by_reg(&scopes[i], pc, reg, > - &type_offset, is_fbreg, &var_die)) > + &mem_die, &type_offset, is_fbreg, &var_die)) > continue; > + result = PERF_TMR_OK; > } > > pr_debug_dtp("found \"%s\" (die: %#lx) in scope=%d/%d (die: %#lx) ", > dwarf_diename(&var_die), (long)dwarf_dieoffset(&var_die), > i+1, nr_scopes, (long)dwarf_dieoffset(&scopes[i])); > > - /* Found a variable, see if it's correct */ > - result = check_variable(dloc, &var_die, &mem_die, reg, type_offset, is_fbreg); > if (result == PERF_TMR_OK) { > if (reg == DWARF_REG_PC) { > pr_debug_dtp("addr=%#"PRIx64" type_offset=%#x\n", > @@ -1575,7 +1577,9 @@ static int find_data_type_die(struct data_loc_info *dloc, Dwarf_Die *type_die) > pr_debug_dtp("type_offset=%#x\n", type_offset); > } > > - if (!found || is_better_type(type_die, &mem_die)) { > + if (!found || dloc->type_offset < type_offset || > + (dloc->type_offset == type_offset && > + is_better_type(type_die, &mem_die))) { > *type_die = mem_die; > dloc->type_offset = type_offset; > found = true; > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c > index 6e8877ff2172..56e1b5690dc4 100644 > --- a/tools/perf/util/dwarf-aux.c > +++ b/tools/perf/util/dwarf-aux.c > @@ -1378,6 +1378,8 @@ struct find_var_data { > Dwarf_Addr addr; > /* Target register */ > unsigned reg; > + /* Access data type */ > + Dwarf_Die type; > /* Access offset, set for global data */ > int offset; > /* True if the current register is the frame base */ > @@ -1390,29 +1392,28 @@ struct find_var_data { > static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data, > s64 addr_offset, s64 addr_type, bool is_pointer) > { > - Dwarf_Die type_die; > Dwarf_Word size; > s64 offset = addr_offset - addr_type; > > - if (offset == 0) { > - /* Update offset relative to the start of the variable */ > - data->offset = 0; > - return true; > - } > - > if (offset < 0) > return false; > > - if (die_get_real_type(die_mem, &type_die) == NULL) > + if (__die_get_real_type(die_mem, &data->type) == NULL) > return false; > > - if (is_pointer && dwarf_tag(&type_die) == DW_TAG_pointer_type) { > + if (is_pointer && dwarf_tag(&data->type) == DW_TAG_pointer_type) { > /* Get the target type of the pointer */ > - if (die_get_real_type(&type_die, &type_die) == NULL) > + if (__die_get_real_type(&data->type, &data->type) == NULL) > return false; > } > > - if (dwarf_aggregate_size(&type_die, &size) < 0) > + if (offset == 0) { > + /* Update offset relative to the start of the variable */ > + data->offset = 0; > + return true; > + } > + > + if (dwarf_aggregate_size(&data->type, &size) < 0) > return false; > > if ((u64)offset >= size) > @@ -1529,7 +1530,7 @@ static int __die_find_var_reg_cb(Dwarf_Die *die_mem, void *arg) > * when the variable is in the stack. > */ > Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg, > - int *poffset, bool is_fbreg, > + Dwarf_Die *type_die, int *poffset, bool is_fbreg, > Dwarf_Die *die_mem) > { > struct find_var_data data = { > @@ -1541,8 +1542,11 @@ Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg, > Dwarf_Die *result; > > result = die_find_child(sc_die, __die_find_var_reg_cb, &data, die_mem); > - if (result) > + if (result) { > *poffset = data.offset; > + *type_die = data.type; > + } > + > return result; > } > > diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h > index f20319eb97a9..beb6926aaa71 100644 > --- a/tools/perf/util/dwarf-aux.h > +++ b/tools/perf/util/dwarf-aux.h > @@ -167,7 +167,7 @@ int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die, struct strbuf *buf); > > /* Find a variable saved in the 'reg' at given address */ > Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg, > - int *poffset, bool is_fbreg, > + Dwarf_Die *type_die, int *poffset, bool is_fbreg, > Dwarf_Die *die_mem); > > /* Find a (global) variable located in the 'addr' */ > -- > 2.51.0.261.g7ce5a0a67e-goog >