From d60469d7c0e5c4e8de10699377d2ba79004236a4 Mon Sep 17 00:00:00 2001 From: Namhyung Kim Date: Thu, 9 Nov 2023 15:59:51 -0800 Subject: [PATCH] perf dwarf-aux: Add die_find_variable_by_addr() The die_find_variable_by_addr() is to find a variables in the given DIE using given (PC-relative) address. Global variables will have a location expression with DW_OP_addr which has an address so can simply compare it with the address. <1><143a7>: Abbrev Number: 2 (DW_TAG_variable) <143a8> DW_AT_name : loops_per_jiffy <143ac> DW_AT_type : <0x1cca> <143b0> DW_AT_external : 1 <143b0> DW_AT_decl_file : 193 <143b1> DW_AT_decl_line : 213 <143b2> DW_AT_location : 9 byte block: 3 b0 46 41 82 ff ff ff ff (DW_OP_addr: ffffffff824146b0) Note that the type-offset should be calculated from the base address of the global variable. Signed-off-by: Namhyung Kim Acked-by: Masami Hiramatsu (Google) Cc: Adrian Hunter Cc: Andi Kleen Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: linux-toolchains@vger.kernel.org Cc: linux-trace-devel@vger.kernel.org Link: https://lore.kernel.org/r/20231110000012.3538610-33-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/dwarf-aux.c | 79 +++++++++++++++++++++++++++++++++++++ tools/perf/util/dwarf-aux.h | 14 +++++++ 2 files changed, 93 insertions(+) diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c index 652e6e7368a2..edd9e407bc74 100644 --- a/tools/perf/util/dwarf-aux.c +++ b/tools/perf/util/dwarf-aux.c @@ -1250,8 +1250,12 @@ out: struct find_var_data { /* Target instruction address */ Dwarf_Addr pc; + /* Target memory address (for global data) */ + Dwarf_Addr addr; /* Target register */ unsigned reg; + /* Access offset, set for global data */ + int offset; }; /* Max number of registers DW_OP_regN supports */ @@ -1312,6 +1316,81 @@ Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg, }; return die_find_child(sc_die, __die_find_var_reg_cb, &data, die_mem); } + +/* Only checks direct child DIEs in the given scope */ +static int __die_find_var_addr_cb(Dwarf_Die *die_mem, void *arg) +{ + struct find_var_data *data = arg; + int tag = dwarf_tag(die_mem); + ptrdiff_t off = 0; + Dwarf_Attribute attr; + Dwarf_Addr base, start, end; + Dwarf_Word size; + Dwarf_Die type_die; + Dwarf_Op *ops; + size_t nops; + + if (tag != DW_TAG_variable) + return DIE_FIND_CB_SIBLING; + + if (dwarf_attr(die_mem, DW_AT_location, &attr) == NULL) + return DIE_FIND_CB_SIBLING; + + while ((off = dwarf_getlocations(&attr, off, &base, &start, &end, &ops, &nops)) > 0) { + if (ops->atom != DW_OP_addr) + continue; + + if (data->addr < ops->number) + continue; + + if (data->addr == ops->number) { + /* Update offset relative to the start of the variable */ + data->offset = 0; + return DIE_FIND_CB_END; + } + + if (die_get_real_type(die_mem, &type_die) == NULL) + continue; + + if (dwarf_aggregate_size(&type_die, &size) < 0) + continue; + + if (data->addr >= ops->number + size) + continue; + + /* Update offset relative to the start of the variable */ + data->offset = data->addr - ops->number; + return DIE_FIND_CB_END; + } + return DIE_FIND_CB_SIBLING; +} + +/** + * die_find_variable_by_addr - Find variable located at given address + * @sc_die: a scope DIE + * @pc: the program address to find + * @addr: the data address to find + * @die_mem: a buffer to save the resulting DIE + * @offset: the offset in the resulting type + * + * Find the variable DIE located at the given address (in PC-relative mode). + * This is usually for global variables. + */ +Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr pc, + Dwarf_Addr addr, Dwarf_Die *die_mem, + int *offset) +{ + struct find_var_data data = { + .pc = pc, + .addr = addr, + }; + Dwarf_Die *result; + + result = die_find_child(sc_die, __die_find_var_addr_cb, &data, die_mem); + if (result) + *offset = data.offset; + return result; +} #endif /* diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h index b6f430730bd1..0ddf61fd3f8b 100644 --- a/tools/perf/util/dwarf-aux.h +++ b/tools/perf/util/dwarf-aux.h @@ -141,6 +141,11 @@ int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die, struct strbuf *buf); Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die, Dwarf_Addr pc, int reg, Dwarf_Die *die_mem); +/* Find a (global) variable located in the 'addr' */ +Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die, Dwarf_Addr pc, + Dwarf_Addr addr, Dwarf_Die *die_mem, + int *offset); + #else /* HAVE_DWARF_GETLOCATIONS_SUPPORT */ static inline int die_get_var_range(Dwarf_Die *sp_die __maybe_unused, @@ -158,6 +163,15 @@ static inline Dwarf_Die *die_find_variable_by_reg(Dwarf_Die *sc_die __maybe_unus return NULL; } +static inline Dwarf_Die *die_find_variable_by_addr(Dwarf_Die *sc_die __maybe_unused, + Dwarf_Addr pc __maybe_unused, + Dwarf_Addr addr __maybe_unused, + Dwarf_Die *die_mem __maybe_unused, + int *offset __maybe_unused) +{ + return NULL; +} + #endif /* HAVE_DWARF_GETLOCATIONS_SUPPORT */ #endif /* _DWARF_AUX_H */