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authorKan Liang <kan.liang@intel.com>2017-08-29 03:52:49 +0300
committerIngo Molnar <mingo@kernel.org>2017-08-29 16:09:25 +0300
commitfc7ce9c74c3ad232b084d80148654f926d01ece7 (patch)
treedc7be53c4a52480c3acd480036e2686b84b56951 /kernel/events
parent8d4e6c4caa12dafbcba138e5450b7af17b0b2194 (diff)
downloadlinux-fc7ce9c74c3ad232b084d80148654f926d01ece7.tar.xz
perf/core, x86: Add PERF_SAMPLE_PHYS_ADDR
For understanding how the workload maps to memory channels and hardware behavior, it's very important to collect address maps with physical addresses. For example, 3D XPoint access can only be found by filtering the physical address. Add a new sample type for physical address. perf already has a facility to collect data virtual address. This patch introduces a function to convert the virtual address to physical address. The function is quite generic and can be extended to any architecture as long as a virtual address is provided. - For kernel direct mapping addresses, virt_to_phys is used to convert the virtual addresses to physical address. - For user virtual addresses, __get_user_pages_fast is used to walk the pages tables for user physical address. - This does not work for vmalloc addresses right now. These are not resolved, but code to do that could be added. The new sample type requires collecting the virtual address. The virtual address will not be output unless SAMPLE_ADDR is applied. For security, the physical address can only be exposed to root or privileged user. Tested-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com> Signed-off-by: Kan Liang <kan.liang@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: acme@kernel.org Cc: mpe@ellerman.id.au Link: http://lkml.kernel.org/r/1503967969-48278-1-git-send-email-kan.liang@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/core.c46
1 files changed, 46 insertions, 0 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 77fd6b11ef22..ce64f3fed5c6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1575,6 +1575,9 @@ static void __perf_event_header_size(struct perf_event *event, u64 sample_type)
if (sample_type & PERF_SAMPLE_TRANSACTION)
size += sizeof(data->txn);
+ if (sample_type & PERF_SAMPLE_PHYS_ADDR)
+ size += sizeof(data->phys_addr);
+
event->header_size = size;
}
@@ -6017,6 +6020,9 @@ void perf_output_sample(struct perf_output_handle *handle,
}
}
+ if (sample_type & PERF_SAMPLE_PHYS_ADDR)
+ perf_output_put(handle, data->phys_addr);
+
if (!event->attr.watermark) {
int wakeup_events = event->attr.wakeup_events;
@@ -6032,6 +6038,38 @@ void perf_output_sample(struct perf_output_handle *handle,
}
}
+static u64 perf_virt_to_phys(u64 virt)
+{
+ u64 phys_addr = 0;
+ struct page *p = NULL;
+
+ if (!virt)
+ return 0;
+
+ if (virt >= TASK_SIZE) {
+ /* If it's vmalloc()d memory, leave phys_addr as 0 */
+ if (virt_addr_valid((void *)(uintptr_t)virt) &&
+ !(virt >= VMALLOC_START && virt < VMALLOC_END))
+ phys_addr = (u64)virt_to_phys((void *)(uintptr_t)virt);
+ } else {
+ /*
+ * Walking the pages tables for user address.
+ * Interrupts are disabled, so it prevents any tear down
+ * of the page tables.
+ * Try IRQ-safe __get_user_pages_fast first.
+ * If failed, leave phys_addr as 0.
+ */
+ if ((current->mm != NULL) &&
+ (__get_user_pages_fast(virt, 1, 0, &p) == 1))
+ phys_addr = page_to_phys(p) + virt % PAGE_SIZE;
+
+ if (p)
+ put_page(p);
+ }
+
+ return phys_addr;
+}
+
void perf_prepare_sample(struct perf_event_header *header,
struct perf_sample_data *data,
struct perf_event *event,
@@ -6150,6 +6188,9 @@ void perf_prepare_sample(struct perf_event_header *header,
header->size += size;
}
+
+ if (sample_type & PERF_SAMPLE_PHYS_ADDR)
+ data->phys_addr = perf_virt_to_phys(data->addr);
}
static void __always_inline
@@ -9909,6 +9950,11 @@ SYSCALL_DEFINE5(perf_event_open,
return -EINVAL;
}
+ /* Only privileged users can get physical addresses */
+ if ((attr.sample_type & PERF_SAMPLE_PHYS_ADDR) &&
+ perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
+ return -EACCES;
+
if (!attr.sample_max_stack)
attr.sample_max_stack = sysctl_perf_event_max_stack;