branch_stack struct has bit field definition which
produces different bit ordering for big/little endian.
Because of this, when branch_stack sample is collected
in a BE system and viewed/reported in a LE system, bit
fields of the branch stack are not presented properly.
To address this issue, a evsel__bitfield_swap_branch_stack()
is defined and introduced in evsel__parse_sample.
Signed-off-by: Madhavan Srinivasan <[email protected]>
---
Changelog v2:
- used tep_is_bigendian() instead bigendian()
to avoid perf test python fail.
Changelog v1:
- Renamed function and macro
- Added comments in code
tools/perf/util/evsel.c | 77 +++++++++++++++++++++++++++++++++++++++--
tools/perf/util/evsel.h | 13 +++++++
2 files changed, 88 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index dbfeceb2546c..4e929b9d9718 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2221,6 +2221,54 @@ void __weak arch_perf_parse_sample_weight(struct perf_sample *data,
data->weight = *array;
}
+u64 evsel__bitfield_swap_branch_flags(u64 value)
+{
+ u64 new_val = 0;
+
+ /*
+ * branch_flags
+ * union {
+ * u64 values;
+ * struct {
+ * mispred:1 //target mispredicted
+ * predicted:1 //target predicted
+ * in_tx:1 //in transaction
+ * abort:1 //transaction abort
+ * cycles:16 //cycle count to last branch
+ * type:4 //branch type
+ * reserved:40
+ * }
+ * }
+ *
+ * Avoid bswap64() the entire branch_flag.value,
+ * as it has variable bit-field sizes. Instead the
+ * macro takes the bit-field position/size,
+ * swaps it based on the host endianness.
+ *
+ * tep_is_bigendian() is used here instead of
+ * bigendian() to avoid python test fails.
+ */
+ if (tep_is_bigendian()) {
+ new_val = bitfield_swap(value, 0, 1);
+ new_val |= bitfield_swap(value, 1, 1);
+ new_val |= bitfield_swap(value, 2, 1);
+ new_val |= bitfield_swap(value, 3, 1);
+ new_val |= bitfield_swap(value, 4, 16);
+ new_val |= bitfield_swap(value, 20, 4);
+ new_val |= bitfield_swap(value, 24, 40);
+ } else {
+ new_val = bitfield_swap(value, 63, 1);
+ new_val |= bitfield_swap(value, 62, 1);
+ new_val |= bitfield_swap(value, 61, 1);
+ new_val |= bitfield_swap(value, 60, 1);
+ new_val |= bitfield_swap(value, 44, 16);
+ new_val |= bitfield_swap(value, 40, 4);
+ new_val |= bitfield_swap(value, 0, 40);
+ }
+
+ return new_val;
+}
+
int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
struct perf_sample *data)
{
@@ -2408,6 +2456,8 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
if (type & PERF_SAMPLE_BRANCH_STACK) {
const u64 max_branch_nr = UINT64_MAX /
sizeof(struct branch_entry);
+ struct branch_entry *e;
+ unsigned int i;
OVERFLOW_CHECK_u64(array);
data->branch_stack = (struct branch_stack *)array++;
@@ -2416,10 +2466,33 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
return -EFAULT;
sz = data->branch_stack->nr * sizeof(struct branch_entry);
- if (evsel__has_branch_hw_idx(evsel))
+ if (evsel__has_branch_hw_idx(evsel)) {
sz += sizeof(u64);
- else
+ e = &data->branch_stack->entries[0];
+ } else {
data->no_hw_idx = true;
+ /*
+ * if the PERF_SAMPLE_BRANCH_HW_INDEX is not applied,
+ * only nr and entries[] will be output by kernel.
+ */
+ e = (struct branch_entry *)&data->branch_stack->hw_idx;
+ }
+
+ if (swapped) {
+ /*
+ * struct branch_flag does not have endian
+ * specific bit field definition. And bswap
+ * will not resolve the issue, since these
+ * are bit fields.
+ *
+ * evsel__bitfield_swap_branch_flags() uses a
+ * bitfield_swap macro to swap the bit position
+ * based on the host endians.
+ */
+ for (i = 0; i < data->branch_stack->nr; i++, e++)
+ e->flags.value = evsel__bitfield_swap_branch_flags(e->flags.value);
+ }
+
OVERFLOW_CHECK(array, sz, max_size);
array = (void *)array + sz;
}
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 1f7edfa8568a..2e82cdbe2c08 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -482,4 +482,17 @@ struct evsel *evsel__leader(struct evsel *evsel);
bool evsel__has_leader(struct evsel *evsel, struct evsel *leader);
bool evsel__is_leader(struct evsel *evsel);
void evsel__set_leader(struct evsel *evsel, struct evsel *leader);
+
+/*
+ * Macro to swap the bit-field postition and size.
+ * Used when,
+ * - dont need to swap the entire u64 &&
+ * - when u64 has variable bit-field sizes &&
+ * - when presented in a host endian which is different
+ * than the source endian of the perf.data file
+ */
+#define bitfield_swap(src, pos, size) \
+ ((((src) >> (pos)) & ((1ull << (size)) - 1)) << (63 - ((pos) + (size) - 1)))
+
+u64 evsel__bitfield_swap_branch_flags(u64 value);
#endif /* __PERF_EVSEL_H */
--
2.31.1
Extend sample-parsing test to include branch_flag
bitfield-endian swap test. Patch include "util/trace-event.h"
to sample-parsing for importing tep_is_bigendian() and
extends samples_same() to include "needs_swap" to
detect/enable check for bitfield-endian swap.
Signed-off-by: Madhavan Srinivasan <[email protected]>
---
Changelog v2:
- used tep_is_bigendian() instead bigendian()
to avoid perf test python fail.
- Updated commit message
Changelog v1:
- Updated commit message
tools/perf/tests/sample-parsing.c | 43 +++++++++++++++++++++++++++----
1 file changed, 38 insertions(+), 5 deletions(-)
diff --git a/tools/perf/tests/sample-parsing.c b/tools/perf/tests/sample-parsing.c
index 8fd8a4ef97da..c83a11514129 100644
--- a/tools/perf/tests/sample-parsing.c
+++ b/tools/perf/tests/sample-parsing.c
@@ -13,6 +13,7 @@
#include "evsel.h"
#include "debug.h"
#include "util/synthetic-events.h"
+#include "util/trace-event.h"
#include "tests.h"
@@ -30,9 +31,18 @@
} \
} while (0)
+/*
+ * Hardcode the expected values for branch_entry flags.
+ * These are based on the input value (213) specified
+ * in branch_stack variable.
+ */
+#define BS_EXPECTED_BE 0xa00d000000000000
+#define BS_EXPECTED_LE 0xd5000000
+#define FLAG(s) s->branch_stack->entries[i].flags
+
static bool samples_same(const struct perf_sample *s1,
const struct perf_sample *s2,
- u64 type, u64 read_format)
+ u64 type, u64 read_format, bool needs_swap)
{
size_t i;
@@ -100,8 +110,14 @@ static bool samples_same(const struct perf_sample *s1,
if (type & PERF_SAMPLE_BRANCH_STACK) {
COMP(branch_stack->nr);
COMP(branch_stack->hw_idx);
- for (i = 0; i < s1->branch_stack->nr; i++)
- MCOMP(branch_stack->entries[i]);
+ for (i = 0; i < s1->branch_stack->nr; i++) {
+ if (needs_swap)
+ return ((tep_is_bigendian()) ?
+ (FLAG(s2).value == BS_EXPECTED_BE) :
+ (FLAG(s2).value == BS_EXPECTED_LE));
+ else
+ MCOMP(branch_stack->entries[i]);
+ }
}
if (type & PERF_SAMPLE_REGS_USER) {
@@ -248,7 +264,7 @@ static int do_test(u64 sample_type, u64 sample_regs, u64 read_format)
},
};
struct sample_read_value values[] = {{1, 5}, {9, 3}, {2, 7}, {6, 4},};
- struct perf_sample sample_out;
+ struct perf_sample sample_out, sample_out_endian;
size_t i, sz, bufsz;
int err, ret = -1;
@@ -313,12 +329,29 @@ static int do_test(u64 sample_type, u64 sample_regs, u64 read_format)
goto out_free;
}
- if (!samples_same(&sample, &sample_out, sample_type, read_format)) {
+ if (!samples_same(&sample, &sample_out, sample_type, read_format, evsel.needs_swap)) {
pr_debug("parsing failed for sample_type %#"PRIx64"\n",
sample_type);
goto out_free;
}
+ if (sample_type == PERF_SAMPLE_BRANCH_STACK) {
+ evsel.needs_swap = true;
+ evsel.sample_size = __evsel__sample_size(sample_type);
+ err = evsel__parse_sample(&evsel, event, &sample_out_endian);
+ if (err) {
+ pr_debug("%s failed for sample_type %#"PRIx64", error %d\n",
+ "evsel__parse_sample", sample_type, err);
+ goto out_free;
+ }
+
+ if (!samples_same(&sample, &sample_out_endian, sample_type, read_format, evsel.needs_swap)) {
+ pr_debug("parsing failed for sample_type %#"PRIx64"\n",
+ sample_type);
+ goto out_free;
+ }
+ }
+
ret = 0;
out_free:
free(event);
--
2.31.1
Em Thu, Oct 28, 2021 at 05:07:13PM +0530, Madhavan Srinivasan escreveu:
> branch_stack struct has bit field definition which
> produces different bit ordering for big/little endian.
> Because of this, when branch_stack sample is collected
> in a BE system and viewed/reported in a LE system, bit
> fields of the branch stack are not presented properly.
> To address this issue, a evsel__bitfield_swap_branch_stack()
> is defined and introduced in evsel__parse_sample.
Jiri,
This is a minor change, he just switched to an inline equivalent
(the code is slightly different, but should be ok), can I apply yout
v2 Acked-by tags?
- Arnaldo
> Signed-off-by: Madhavan Srinivasan <[email protected]>
> ---
> Changelog v2:
> - used tep_is_bigendian() instead bigendian()
> to avoid perf test python fail.
>
> Changelog v1:
> - Renamed function and macro
> - Added comments in code
>
> tools/perf/util/evsel.c | 77 +++++++++++++++++++++++++++++++++++++++--
> tools/perf/util/evsel.h | 13 +++++++
> 2 files changed, 88 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index dbfeceb2546c..4e929b9d9718 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -2221,6 +2221,54 @@ void __weak arch_perf_parse_sample_weight(struct perf_sample *data,
> data->weight = *array;
> }
>
> +u64 evsel__bitfield_swap_branch_flags(u64 value)
> +{
> + u64 new_val = 0;
> +
> + /*
> + * branch_flags
> + * union {
> + * u64 values;
> + * struct {
> + * mispred:1 //target mispredicted
> + * predicted:1 //target predicted
> + * in_tx:1 //in transaction
> + * abort:1 //transaction abort
> + * cycles:16 //cycle count to last branch
> + * type:4 //branch type
> + * reserved:40
> + * }
> + * }
> + *
> + * Avoid bswap64() the entire branch_flag.value,
> + * as it has variable bit-field sizes. Instead the
> + * macro takes the bit-field position/size,
> + * swaps it based on the host endianness.
> + *
> + * tep_is_bigendian() is used here instead of
> + * bigendian() to avoid python test fails.
> + */
> + if (tep_is_bigendian()) {
> + new_val = bitfield_swap(value, 0, 1);
> + new_val |= bitfield_swap(value, 1, 1);
> + new_val |= bitfield_swap(value, 2, 1);
> + new_val |= bitfield_swap(value, 3, 1);
> + new_val |= bitfield_swap(value, 4, 16);
> + new_val |= bitfield_swap(value, 20, 4);
> + new_val |= bitfield_swap(value, 24, 40);
> + } else {
> + new_val = bitfield_swap(value, 63, 1);
> + new_val |= bitfield_swap(value, 62, 1);
> + new_val |= bitfield_swap(value, 61, 1);
> + new_val |= bitfield_swap(value, 60, 1);
> + new_val |= bitfield_swap(value, 44, 16);
> + new_val |= bitfield_swap(value, 40, 4);
> + new_val |= bitfield_swap(value, 0, 40);
> + }
> +
> + return new_val;
> +}
> +
> int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
> struct perf_sample *data)
> {
> @@ -2408,6 +2456,8 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
> if (type & PERF_SAMPLE_BRANCH_STACK) {
> const u64 max_branch_nr = UINT64_MAX /
> sizeof(struct branch_entry);
> + struct branch_entry *e;
> + unsigned int i;
>
> OVERFLOW_CHECK_u64(array);
> data->branch_stack = (struct branch_stack *)array++;
> @@ -2416,10 +2466,33 @@ int evsel__parse_sample(struct evsel *evsel, union perf_event *event,
> return -EFAULT;
>
> sz = data->branch_stack->nr * sizeof(struct branch_entry);
> - if (evsel__has_branch_hw_idx(evsel))
> + if (evsel__has_branch_hw_idx(evsel)) {
> sz += sizeof(u64);
> - else
> + e = &data->branch_stack->entries[0];
> + } else {
> data->no_hw_idx = true;
> + /*
> + * if the PERF_SAMPLE_BRANCH_HW_INDEX is not applied,
> + * only nr and entries[] will be output by kernel.
> + */
> + e = (struct branch_entry *)&data->branch_stack->hw_idx;
> + }
> +
> + if (swapped) {
> + /*
> + * struct branch_flag does not have endian
> + * specific bit field definition. And bswap
> + * will not resolve the issue, since these
> + * are bit fields.
> + *
> + * evsel__bitfield_swap_branch_flags() uses a
> + * bitfield_swap macro to swap the bit position
> + * based on the host endians.
> + */
> + for (i = 0; i < data->branch_stack->nr; i++, e++)
> + e->flags.value = evsel__bitfield_swap_branch_flags(e->flags.value);
> + }
> +
> OVERFLOW_CHECK(array, sz, max_size);
> array = (void *)array + sz;
> }
> diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
> index 1f7edfa8568a..2e82cdbe2c08 100644
> --- a/tools/perf/util/evsel.h
> +++ b/tools/perf/util/evsel.h
> @@ -482,4 +482,17 @@ struct evsel *evsel__leader(struct evsel *evsel);
> bool evsel__has_leader(struct evsel *evsel, struct evsel *leader);
> bool evsel__is_leader(struct evsel *evsel);
> void evsel__set_leader(struct evsel *evsel, struct evsel *leader);
> +
> +/*
> + * Macro to swap the bit-field postition and size.
> + * Used when,
> + * - dont need to swap the entire u64 &&
> + * - when u64 has variable bit-field sizes &&
> + * - when presented in a host endian which is different
> + * than the source endian of the perf.data file
> + */
> +#define bitfield_swap(src, pos, size) \
> + ((((src) >> (pos)) & ((1ull << (size)) - 1)) << (63 - ((pos) + (size) - 1)))
> +
> +u64 evsel__bitfield_swap_branch_flags(u64 value);
> #endif /* __PERF_EVSEL_H */
> --
> 2.31.1
--
- Arnaldo