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perf probe: Show correct statement line number by perf probe -l 

The dwarf_getsrc_die() can return the line which is not a statement nor
the least line number among the lines which shares same address.

This can lead perf probe --list shows incorrect line number for probed
address.

To fix this, this introduces cu_getsrc_die() which returns only a
statement line and which is the least line number (we call it the
representive line for an address), and use it in cu_find_lineinfo().

Also, if the given address is the entry address of a real function,
cu_find_lineinfo() returns the function declared line number instead of
the start line number of the function body.

For example, without this change perf probe -l shows incorrect line as
below.

  # perf probe -a kernel_read:2
  Added new event:
    probe:kernel_read    (on kernel_read:2)

  You can now use it in all perf tools, such as:

  	perf record -e probe:kernel_read -aR sleep 1

  # perf probe -l
    probe:kernel_read    (on kernel_read:1@linux-5.0.0/fs/read_write.c)

With this fix, it shows correct line number as below;

  # perf probe -l
    probe:kernel_read    (on kernel_read:2@linux-5.0.0/fs/read_write.c)

Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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/157406471067.24476.17463149618465494448.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Masami Hiramatsu 2019-11-18 17:11:50 +09:00 committed by Arnaldo Carvalho de Melo
parent b980be189c
commit 57f95bf5f8
1 changed files with 58 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

62
tools/perf/util/dwarf-aux.c
View File

@ -59,6 +59,51 @@ const char *cu_get_comp_dir(Dwarf_Die *cu_die)
return dwarf_formstring(&attr);
}
/* Unlike dwarf_getsrc_die(), cu_getsrc_die() only returns statement line */
static Dwarf_Line *cu_getsrc_die(Dwarf_Die *cu_die, Dwarf_Addr addr)
{
Dwarf_Addr laddr;
Dwarf_Lines *lines;
Dwarf_Line *line;
size_t nlines, l, u, n;
bool flag;
if (dwarf_getsrclines(cu_die, &lines, &nlines) != 0 ||
nlines == 0)
return NULL;
/* Lines are sorted by address, use binary search */
l = 0; u = nlines - 1;
while (l < u) {
n = u - (u - l) / 2;
line = dwarf_onesrcline(lines, n);
if (!line || dwarf_lineaddr(line, &laddr) != 0)
return NULL;
if (addr < laddr)
u = n - 1;
else
l = n;
}
/* Going backward to find the lowest line */
do {
line = dwarf_onesrcline(lines, --l);
if (!line || dwarf_lineaddr(line, &laddr) != 0)
return NULL;
} while (laddr == addr);
l++;
/* Going foward to find the statement line */
do {
line = dwarf_onesrcline(lines, l++);
if (!line || dwarf_lineaddr(line, &laddr) != 0 ||
dwarf_linebeginstatement(line, &flag) != 0)
return NULL;
if (laddr > addr)
return NULL;
} while (!flag);
return line;
}
/**
* cu_find_lineinfo - Get a line number and file name for given address
* @cu_die: a CU DIE
@ -72,17 +117,26 @@ int cu_find_lineinfo(Dwarf_Die *cu_die, unsigned long addr,
const char **fname, int *lineno)
{
Dwarf_Line *line;
Dwarf_Addr laddr;
Dwarf_Die die_mem;
Dwarf_Addr faddr;
line = dwarf_getsrc_die(cu_die, (Dwarf_Addr)addr);
if (line && dwarf_lineaddr(line, &laddr) == 0 &&
addr == (unsigned long)laddr && dwarf_lineno(line, lineno) == 0) {
if (die_find_realfunc(cu_die, (Dwarf_Addr)addr, &die_mem)
&& die_entrypc(&die_mem, &faddr) == 0 &&
faddr == addr) {
*fname = dwarf_decl_file(&die_mem);
dwarf_decl_line(&die_mem, lineno);
goto out;
}
line = cu_getsrc_die(cu_die, (Dwarf_Addr)addr);
if (line && dwarf_lineno(line, lineno) == 0) {
*fname = dwarf_linesrc(line, NULL, NULL);
if (!*fname)
/* line number is useless without filename */
*lineno = 0;
}
out:
return *lineno ?: -ENOENT;
}