Commit 66f69b21 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Arnaldo Carvalho de Melo
Browse files

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: default avatarMasami 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 72363540

tools/perf/util/probe-file.c

+7 −0
Original line number Diff line number Diff line
@@ -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);

}

tools/perf/util/probe-file.h

+1 −0
Original line number Diff line number Diff line
@@ -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)

{

tools/perf/util/probe-finder.c

+11 −0
Original line number Diff line number Diff line
@@ -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 ? */

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