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perf probe: Support DW_AT_const_value constant value 

Support DW_AT_const_value for variable assignment instead of location.
Note that this requires ftrace supporting immediate value.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Link: http://lore.kernel.org/lkml/157406476012.24476.16096289871757175775.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
alistair/sunxi64-5.5-dsi
Masami Hiramatsu 2019-11-18 17:12:40 +09:00 committed by Arnaldo Carvalho de Melo
parent 72363540c0
commit 66f69b2197
3 changed files with 19 additions and 0 deletions
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7
tools/perf/util/probe-file.c
View File

@ -1008,6 +1008,7 @@ enum ftrace_readme {
FTRACE_README_UPROBE_REF_CTR,
FTRACE_README_USER_ACCESS,
FTRACE_README_MULTIPROBE_EVENT,
FTRACE_README_IMMEDIATE_VALUE,
FTRACE_README_END,
};
@ -1022,6 +1023,7 @@ static struct {
DEFINE_TYPE(FTRACE_README_UPROBE_REF_CTR, "*ref_ctr_offset*"),
DEFINE_TYPE(FTRACE_README_USER_ACCESS, "*[u]<offset>*"),
DEFINE_TYPE(FTRACE_README_MULTIPROBE_EVENT, "*Create/append/*"),
DEFINE_TYPE(FTRACE_README_IMMEDIATE_VALUE, "*\\imm-value,*"),
};
static bool scan_ftrace_readme(enum ftrace_readme type)
@ -1092,3 +1094,8 @@ bool multiprobe_event_is_supported(void)
{
return scan_ftrace_readme(FTRACE_README_MULTIPROBE_EVENT);
}
bool immediate_value_is_supported(void)
{
return scan_ftrace_readme(FTRACE_README_IMMEDIATE_VALUE);
}

1
tools/perf/util/probe-file.h
View File

@ -72,6 +72,7 @@ bool kretprobe_offset_is_supported(void);
bool uprobe_ref_ctr_is_supported(void);
bool user_access_is_supported(void);
bool multiprobe_event_is_supported(void);
bool immediate_value_is_supported(void);
#else /* ! HAVE_LIBELF_SUPPORT */
static inline struct probe_cache *probe_cache__new(const char *tgt __maybe_unused, struct nsinfo *nsi __maybe_unused)
{

11
tools/perf/util/probe-finder.c
View File

@ -177,6 +177,17 @@ static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr,
if (dwarf_attr(vr_die, DW_AT_external, &attr) != NULL)
goto static_var;
/* Constant value */
if (dwarf_attr(vr_die, DW_AT_const_value, &attr) &&
immediate_value_is_supported()) {
Dwarf_Sword snum;
dwarf_formsdata(&attr, &snum);
ret = asprintf(&tvar->value, "\\%ld", (long)snum);
return ret < 0 ? -ENOMEM : 0;
}
/* TODO: handle more than 1 exprs */
if (dwarf_attr(vr_die, DW_AT_location, &attr) == NULL)
return -EINVAL; /* Broken DIE ? */