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Mon, 26 Jan 2026 18:06:34 -0800 (PST) From: Zecheng Li To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim Cc: Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , James Clark , Zecheng Li , xliuprof@google.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, Zecheng Li Subject: [PATCH v1 01/11] perf dwarf-aux: Skip check_variable for die_find_variable_by_reg Date: Mon, 26 Jan 2026 21:04:54 -0500 Message-ID: <20260127020617.2804780-2-zli94@ncsu.edu> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260127020617.2804780-1-zli94@ncsu.edu> References: <20260127020617.2804780-1-zli94@ncsu.edu> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Zecheng Li 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. Return type from die_find_variable_by_reg via a new `type` field in find_var_data. Signed-off-by: Zecheng Li Signed-off-by: Zecheng Li --- tools/perf/util/annotate-data.c | 8 +++++--- tools/perf/util/dwarf-aux.c | 18 +++++++++++------- tools/perf/util/dwarf-aux.h | 2 +- 3 files changed, 17 insertions(+), 11 deletions(-) diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-dat= a.c index 07cf9c334be0..99ffc6d70565 100644 --- a/tools/perf/util/annotate-data.c +++ b/tools/perf/util/annotate-data.c @@ -1603,19 +1603,21 @@ 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 =3D 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 =3D PERF_TMR_OK; } =20 pr_debug_dtp("found \"%s\" (die: %#lx) in scope=3D%d/%d (die: %#lx) ", dwarf_diename(&var_die), (long)dwarf_dieoffset(&var_die), i+1, nr_scopes, (long)dwarf_dieoffset(&scopes[i])); =20 - /* Found a variable, see if it's correct */ - result =3D check_variable(dloc, &var_die, &mem_die, reg, type_offset, is= _fbreg); if (result =3D=3D PERF_TMR_OK) { if (reg =3D=3D DWARF_REG_PC) { pr_debug_dtp("addr=3D%#"PRIx64" type_offset=3D%#x\n", diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c index 9267af204c7d..b57cdc8860f0 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 */ @@ -1390,7 +1392,6 @@ struct find_var_data { static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *dat= a, s64 addr_offset, s64 addr_type, bool is_pointer) { - Dwarf_Die type_die; Dwarf_Word size; s64 offset =3D addr_offset - addr_type; =20 @@ -1403,16 +1404,16 @@ static bool match_var_offset(Dwarf_Die *die_mem, st= ruct find_var_data *data, if (offset < 0) return false; =20 - if (die_get_real_type(die_mem, &type_die) =3D=3D NULL) + if (die_get_real_type(die_mem, &data->type) =3D=3D NULL) return false; =20 - if (is_pointer && dwarf_tag(&type_die) =3D=3D DW_TAG_pointer_type) { + if (is_pointer && dwarf_tag(&data->type) =3D=3D DW_TAG_pointer_type) { /* Get the target type of the pointer */ - if (die_get_real_type(&type_die, &type_die) =3D=3D NULL) + if (die_get_real_type(&data->type, &data->type) =3D=3D NULL) return false; } =20 - if (dwarf_aggregate_size(&type_die, &size) < 0) + if (dwarf_aggregate_size(&data->type, &size) < 0) return false; =20 if ((u64)offset >=3D 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 =3D { @@ -1541,8 +1542,11 @@ Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_di= e, Dwarf_Addr pc, int reg, Dwarf_Die *result; =20 result =3D die_find_child(sc_die, __die_find_var_reg_cb, &data, die_mem); - if (result) + if (result) { *poffset =3D data.offset; + *type_die =3D data.type; + } + return result; } =20 diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h index cd481ec9c5a1..b3ee5df0b6be 100644 --- a/tools/perf/util/dwarf-aux.h +++ b/tools/perf/util/dwarf-aux.h @@ -163,7 +163,7 @@ int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_= die, struct strbuf *buf); =20 /* 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); =20 /* Find a (global) variable located in the 'addr' */ --=20 2.52.0