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| Started by | "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> |
|---|---|
| First post | 2016-04-12 11:20 +0200 |
| Last post | 2016-04-14 03:20 +0200 |
| Articles | 3 — 2 participants |
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[PATCH v2 0/2] perf probe fixes for ppc64le "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2016-04-12 11:20 +0200
[PATCH v2 2/2] perf tools: Fix kallsyms perf test on ppc64le "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2016-04-12 11:20 +0200
Re: [PATCH v2 0/2] perf probe fixes for ppc64le Balbir Singh <bsingharora@gmail.com> - 2016-04-14 03:20 +0200
| From | "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-04-12 11:20 +0200 |
| Subject | [PATCH v2 0/2] perf probe fixes for ppc64le |
| Message-ID | <rn2Ei-4JV-5@gated-at.bofh.it> |
This patchset fixes three issues found with perf probe on ppc64le:
1. 'perf test kallsyms' failure on ppc64le (reported by Michael
Ellerman). This was due to the symbols being fixed up during symbol
table load. This is fixed in patch 2 by delaying symbol fixup until
later.
2. perf probe function offset was being calculated from the local entry
point (LEP), which does not match user expectation when trying to look
at function disassembly output (reported by Ananth N). This is fixed for
kallsyms in patch 1 and for symbol table in patch 2.
3. perf probe failure with kretprobe when using kallsyms. This was
failing as we were specifying an offset. This is fixed in patch 1.
A few examples demonstrating the issues and the fix:
Example for issue (2):
--------------------
# objdump -d vmlinux | grep -A8 \<_do_fork\>:
c0000000000b6a00 <_do_fork>:
c0000000000b6a00: f7 00 4c 3c addis r2,r12,247
c0000000000b6a04: 00 86 42 38 addi r2,r2,-31232
c0000000000b6a08: a6 02 08 7c mflr r0
c0000000000b6a0c: d0 ff 41 fb std r26,-48(r1)
c0000000000b6a10: 26 80 90 7d mfocrf r12,8
c0000000000b6a14: d8 ff 61 fb std r27,-40(r1)
c0000000000b6a18: e0 ff 81 fb std r28,-32(r1)
c0000000000b6a1c: e8 ff a1 fb std r29,-24(r1)
# perf probe -v _do_fork+4
probe-definition(0): _do_fork+4
symbol:_do_fork file:(null) line:0 offset:4 return:0 lazy:(null)
0 arguments
Looking at the vmlinux_path (8 entries long)
Using /proc/kcore for kernel object code
Using /proc/kallsyms for symbols
Opening /sys/kernel/debug/tracing//kprobe_events write=1
Writing event: p:probe/_do_fork _text+748044
Added new event:
probe:_do_fork (on _do_fork+4)
You can now use it in all perf tools, such as:
perf record -e probe:_do_fork -aR sleep 1
# printf "%x\n" 748044
b6a0c
^^^^^
This is offset from the LEP. With this, there is also no way to ever
probe between the GEP and the LEP.
With this patchset:
# perf probe -v _do_fork+4
probe-definition(0): _do_fork+4
symbol:_do_fork file:(null) line:0 offset:4 return:0 lazy:(null)
0 arguments
Looking at the vmlinux_path (8 entries long)
Using /proc/kcore for kernel object code
Using /proc/kallsyms for symbols
Opening /sys/kernel/debug/tracing//kprobe_events write=1
Writing event: p:probe/_do_fork _text+748036
Added new event:
probe:_do_fork (on _do_fork+4)
You can now use it in all perf tools, such as:
perf record -e probe:_do_fork -aR sleep 1
# perf probe -v _do_fork
probe-definition(0): _do_fork
symbol:_do_fork file:(null) line:0 offset:0 return:0 lazy:(null)
0 arguments
Looking at the vmlinux_path (8 entries long)
Using /proc/kcore for kernel object code
Using /proc/kallsyms for symbols
Opening /sys/kernel/debug/tracing//kprobe_events write=1
Writing event: p:probe/_do_fork _text+748040
Added new event:
probe:_do_fork (on _do_fork)
You can now use it in all perf tools, such as:
perf record -e probe:_do_fork -aR sleep 1
We only offset to the LEP if function entry is specified, otherwise, we
offset from the GEP.
Example for issue (3):
---------------------
Before patch:
# perf probe -v _do_fork:%return
probe-definition(0): _do_fork:%return
symbol:_do_fork file:(null) line:0 offset:0 return:1 lazy:(null)
0 arguments
Looking at the vmlinux_path (8 entries long)
Using /proc/kcore for kernel object code
Using /proc/kallsyms for symbols
Opening /sys/kernel/debug/tracing//kprobe_events write=1
Writing event: r:probe/_do_fork _do_fork+8
Failed to write event: Invalid argument
Error: Failed to add events. Reason: Invalid argument (Code: -22)
After patch:
# perf probe _do_fork:%return
Added new event:
probe:_do_fork (on _do_fork%return)
You can now use it in all perf tools, such as:
perf record -e probe:_do_fork -aR sleep 1
Concept Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mark Wielaard <mjw@redhat.com>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Naveen N. Rao (2):
perf tools: Fix kprobe and kretprobe handling with kallsyms on ppc64le
perf tools: Fix kallsyms perf test on ppc64le
tools/perf/arch/powerpc/util/sym-handling.c | 43 +++++++++++++++++++++--------
tools/perf/util/probe-event.c | 5 ++--
tools/perf/util/probe-event.h | 3 +-
tools/perf/util/symbol-elf.c | 7 +++--
tools/perf/util/symbol.h | 3 +-
5 files changed, 43 insertions(+), 18 deletions(-)
--
2.7.4
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| From | "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> |
|---|---|
| Date | 2016-04-12 11:20 +0200 |
| Subject | [PATCH v2 2/2] perf tools: Fix kallsyms perf test on ppc64le |
| Message-ID | <rn2Ej-4JV-27@gated-at.bofh.it> |
| In reply to | #1376577 |
ppc64le functions have a Global Entry Point (GEP) and a Local Entry
Point (LEP). While placing a probe, we always prefer the LEP since it
catches function calls through both the GEP and the LEP. In order to do
this, we fixup the function entry points during elf symbol table lookup
to point to the LEPs. This works, but breaks 'perf test kallsyms' since
the symbols loaded from the symbol table (pointing to the LEP) do not
match the symbols in kallsyms.
To fix this, we do not adjust all the symbols during symbol table load.
Instead, we note down st_other in a newly introduced arch-specific
member of perf symbol structure, and later use this to adjust the probe
trace point.
Cc: Mark Wielaard <mjw@redhat.com>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Reported-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
v2: Added uprobes handling -- we modify the probe address, rather than
the offset.
tools/perf/arch/powerpc/util/sym-handling.c | 28 ++++++++++++++++++++--------
tools/perf/util/probe-event.c | 5 +++--
tools/perf/util/probe-event.h | 3 ++-
tools/perf/util/symbol-elf.c | 7 ++++---
tools/perf/util/symbol.h | 3 ++-
5 files changed, 31 insertions(+), 15 deletions(-)
diff --git a/tools/perf/arch/powerpc/util/sym-handling.c b/tools/perf/arch/powerpc/util/sym-handling.c
index 6974ba0..c6d0f91 100644
--- a/tools/perf/arch/powerpc/util/sym-handling.c
+++ b/tools/perf/arch/powerpc/util/sym-handling.c
@@ -19,12 +19,6 @@ bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
ehdr.e_type == ET_DYN;
}
-#if defined(_CALL_ELF) && _CALL_ELF == 2
-void arch__elf_sym_adjust(GElf_Sym *sym)
-{
- sym->st_value += PPC64_LOCAL_ENTRY_OFFSET(sym->st_other);
-}
-#endif
#endif
#if !defined(_CALL_ELF) || _CALL_ELF != 2
@@ -65,11 +59,21 @@ bool arch__prefers_symtab(void)
return true;
}
+#ifdef HAVE_LIBELF_SUPPORT
+void arch__sym_update(struct symbol *s, GElf_Sym *sym)
+{
+ s->arch_sym = sym->st_other;
+}
+#endif
+
#define PPC64LE_LEP_OFFSET 8
void arch__fix_tev_from_maps(struct perf_probe_event *pev,
- struct probe_trace_event *tev, struct map *map)
+ struct probe_trace_event *tev, struct map *map,
+ struct symbol *sym)
{
+ int lep_offset;
+
/*
* When probing at a function entry point, we normally always want the
* LEP since that catches calls to the function through both the GEP and
@@ -82,10 +86,18 @@ void arch__fix_tev_from_maps(struct perf_probe_event *pev,
*
* In addition, we shouldn't specify an offset for kretprobes.
*/
- if (pev->point.offset || pev->point.retprobe || !map)
+ if (pev->point.offset || pev->point.retprobe || !map || !sym)
return;
+ lep_offset = PPC64_LOCAL_ENTRY_OFFSET(sym->arch_sym);
+
if (map->dso->symtab_type == DSO_BINARY_TYPE__KALLSYMS)
tev->point.offset += PPC64LE_LEP_OFFSET;
+ else if (lep_offset) {
+ if (pev->uprobes)
+ tev->point.address += lep_offset;
+ else
+ tev->point.offset += lep_offset;
+ }
}
#endif
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index 8319fbb..d786a49 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -2498,7 +2498,8 @@ static int find_probe_functions(struct map *map, char *name,
void __weak arch__fix_tev_from_maps(struct perf_probe_event *pev __maybe_unused,
struct probe_trace_event *tev __maybe_unused,
- struct map *map __maybe_unused) { }
+ struct map *map __maybe_unused,
+ struct symbol *sym __maybe_unused) { }
/*
* Find probe function addresses from map.
@@ -2624,7 +2625,7 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
strdup_or_goto(pev->args[i].type,
nomem_out);
}
- arch__fix_tev_from_maps(pev, tev, map);
+ arch__fix_tev_from_maps(pev, tev, map, sym);
}
if (ret == skipped) {
ret = -ENOENT;
diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h
index e54e7b0..9bbc0c1 100644
--- a/tools/perf/util/probe-event.h
+++ b/tools/perf/util/probe-event.h
@@ -154,7 +154,8 @@ int show_available_vars(struct perf_probe_event *pevs, int npevs,
int show_available_funcs(const char *module, struct strfilter *filter, bool user);
bool arch__prefers_symtab(void);
void arch__fix_tev_from_maps(struct perf_probe_event *pev,
- struct probe_trace_event *tev, struct map *map);
+ struct probe_trace_event *tev, struct map *map,
+ struct symbol *sym);
/* If there is no space to write, returns -E2BIG. */
int e_snprintf(char *str, size_t size, const char *format, ...)
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index bc229a7..e6c032e 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -777,7 +777,8 @@ static bool want_demangle(bool is_kernel_sym)
return is_kernel_sym ? symbol_conf.demangle_kernel : symbol_conf.demangle;
}
-void __weak arch__elf_sym_adjust(GElf_Sym *sym __maybe_unused) { }
+void __weak arch__sym_update(struct symbol *s __maybe_unused,
+ GElf_Sym *sym __maybe_unused) { }
int dso__load_sym(struct dso *dso, struct map *map,
struct symsrc *syms_ss, struct symsrc *runtime_ss,
@@ -954,8 +955,6 @@ int dso__load_sym(struct dso *dso, struct map *map,
(sym.st_value & 1))
--sym.st_value;
- arch__elf_sym_adjust(&sym);
-
if (dso->kernel || kmodule) {
char dso_name[PATH_MAX];
@@ -1089,6 +1088,8 @@ new_symbol:
if (!f)
goto out_elf_end;
+ arch__sym_update(f, &sym);
+
if (filter && filter(curr_map, f))
symbol__delete(f);
else {
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index c8b7544..f0e62e8 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -55,6 +55,7 @@ struct symbol {
u16 namelen;
u8 binding;
bool ignore;
+ u8 arch_sym;
char name[0];
};
@@ -310,7 +311,7 @@ int setup_intlist(struct intlist **list, const char *list_str,
#ifdef HAVE_LIBELF_SUPPORT
bool elf__needs_adjust_symbols(GElf_Ehdr ehdr);
-void arch__elf_sym_adjust(GElf_Sym *sym);
+void arch__sym_update(struct symbol *s, GElf_Sym *sym);
#endif
#define SYMBOL_A 0
--
2.7.4
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| From | Balbir Singh <bsingharora@gmail.com> |
|---|---|
| Date | 2016-04-14 03:20 +0200 |
| Message-ID | <rnE6S-1XS-1@gated-at.bofh.it> |
| In reply to | #1376577 |
On 12/04/16 19:10, Naveen N. Rao wrote: > This patchset fixes three issues found with perf probe on ppc64le: > 1. 'perf test kallsyms' failure on ppc64le (reported by Michael > Ellerman). This was due to the symbols being fixed up during symbol > table load. This is fixed in patch 2 by delaying symbol fixup until > later. > 2. perf probe function offset was being calculated from the local entry > point (LEP), which does not match user expectation when trying to look > at function disassembly output (reported by Ananth N). This is fixed for > kallsyms in patch 1 and for symbol table in patch 2. > 3. perf probe failure with kretprobe when using kallsyms. This was > failing as we were specifying an offset. This is fixed in patch 1. > > A few examples demonstrating the issues and the fix: > Given the choices, I think this makes sense Acked-by: Balbir Singh <bsingharora@gmail.com>
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