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Message-ID: <20231012035111.676789-29-namhyung@kernel.org>
Date: Wed, 11 Oct 2023 20:50:51 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
Jiri Olsa <jolsa@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Cc: Ian Rogers <irogers@...gle.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
linux-perf-users@...r.kernel.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Stephane Eranian <eranian@...gle.com>,
Masami Hiramatsu <mhiramat@...nel.org>,
linux-toolchains@...r.kernel.org, linux-trace-devel@...r.kernel.org
Subject: [PATCH 28/48] 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 <namhyung@...nel.org>
---
tools/perf/util/dwarf-aux.c | 80 +++++++++++++++++++++++++++++++++++++
tools/perf/util/dwarf-aux.h | 14 +++++++
2 files changed, 94 insertions(+)
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 5bb05c84d249..97d9ae56350e 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -1266,8 +1266,12 @@ int die_get_var_range(Dwarf_Die *sp_die, Dwarf_Die *vr_die, struct strbuf *buf)
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 */
@@ -1328,6 +1332,82 @@ 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 574405c57d3b..742098e3ee7e 100644
--- a/tools/perf/util/dwarf-aux.h
+++ b/tools/perf/util/dwarf-aux.h
@@ -144,6 +144,11 @@ 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,
@@ -161,6 +166,15 @@ 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 */
--
2.42.0.655.g421f12c284-goog
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