diff options
| -rw-r--r-- | drivers/hwtracing/coresight/coresight-trbe.c | 63 |
1 files changed, 62 insertions, 1 deletions
diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c index 11ff33ec83b9..276862c07e32 100644 --- a/drivers/hwtracing/coresight/coresight-trbe.c +++ b/drivers/hwtracing/coresight/coresight-trbe.c @@ -90,9 +90,11 @@ struct trbe_buf { * - Streamlined detection of erratum across the system */ #define TRBE_WORKAROUND_OVERWRITE_FILL_MODE 0 +#define TRBE_WORKAROUND_WRITE_OUT_OF_RANGE 1 static int trbe_errata_cpucaps[] = { [TRBE_WORKAROUND_OVERWRITE_FILL_MODE] = ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE, + [TRBE_WORKAROUND_WRITE_OUT_OF_RANGE] = ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE, -1, /* Sentinel, must be the last entry */ }; @@ -160,6 +162,11 @@ static inline bool trbe_may_overwrite_in_fill_mode(struct trbe_cpudata *cpudata) return trbe_has_erratum(cpudata, TRBE_WORKAROUND_OVERWRITE_FILL_MODE); } +static inline bool trbe_may_write_out_of_range(struct trbe_cpudata *cpudata) +{ + return trbe_has_erratum(cpudata, TRBE_WORKAROUND_WRITE_OUT_OF_RANGE); +} + static int trbe_alloc_node(struct perf_event *event) { if (event->cpu == -1) @@ -305,7 +312,21 @@ static unsigned long trbe_snapshot_offset(struct perf_output_handle *handle) static u64 trbe_min_trace_buf_size(struct perf_output_handle *handle) { - return TRBE_TRACE_MIN_BUF_SIZE; + u64 size = TRBE_TRACE_MIN_BUF_SIZE; + struct trbe_buf *buf = etm_perf_sink_config(handle); + struct trbe_cpudata *cpudata = buf->cpudata; + + /* + * When the TRBE is affected by an erratum that could make it + * write to the next "virtually addressed" page beyond the LIMIT. + * We need to make sure there is always a PAGE after the LIMIT, + * within the buffer. Thus we ensure there is at least an extra + * page than normal. With this we could then adjust the LIMIT + * pointer down by a PAGE later. + */ + if (trbe_may_write_out_of_range(cpudata)) + size += PAGE_SIZE; + return size; } /* @@ -611,6 +632,17 @@ static unsigned long trbe_get_trace_size(struct perf_output_handle *handle, /* * If the TRBE has wrapped around the write pointer has * wrapped and should be treated as limit. + * + * When the TRBE is affected by TRBE_WORKAROUND_WRITE_OUT_OF_RANGE, + * it may write upto 64bytes beyond the "LIMIT". The driver already + * keeps a valid page next to the LIMIT and we could potentially + * consume the trace data that may have been collected there. But we + * cannot be really sure it is available, and the TRBPTR may not + * indicate the same. Also, affected cores are also affected by another + * erratum which forces the PAGE_SIZE alignment on the TRBPTR, and thus + * could potentially pad an entire PAGE_SIZE - 64bytes, to get those + * 64bytes. Thus we ignore the potential triggering of the erratum + * on WRAP and limit the data to LIMIT. */ if (wrap) write = get_trbe_limit_pointer(); @@ -864,6 +896,35 @@ static int trbe_apply_work_around_before_enable(struct trbe_buf *buf) buf->trbe_write += TRBE_WORKAROUND_OVERWRITE_FILL_MODE_SKIP_BYTES; } + /* + * TRBE_WORKAROUND_WRITE_OUT_OF_RANGE could cause the TRBE to write to + * the next page after the TRBLIMITR.LIMIT. For perf, the "next page" + * may be: + * - The page beyond the ring buffer. This could mean, TRBE could + * corrupt another entity (kernel / user) + * - A portion of the "ring buffer" consumed by the userspace. + * i.e, a page outisde [head, head + size]. + * + * We work around this by: + * - Making sure that we have at least an extra space of PAGE left + * in the ring buffer [head, head + size], than we normally do + * without the erratum. See trbe_min_trace_buf_size(). + * + * - Adjust the TRBLIMITR.LIMIT to leave the extra PAGE outside + * the TRBE's range (i.e [TRBBASER, TRBLIMITR.LIMI] ). + */ + if (trbe_has_erratum(buf->cpudata, TRBE_WORKAROUND_WRITE_OUT_OF_RANGE)) { + s64 space = buf->trbe_limit - buf->trbe_write; + /* + * We must have more than a PAGE_SIZE worth space in the proposed + * range for the TRBE. + */ + if (WARN_ON(space <= PAGE_SIZE || + !IS_ALIGNED(buf->trbe_limit, PAGE_SIZE))) + return -EINVAL; + buf->trbe_limit -= PAGE_SIZE; + } + return 0; } |