Re: [PATCH V8] perf: Add PERF_SAMPLE_PHYS_ADDR
From: Madhavan Srinivasan
Date: Tue Aug 29 2017 - 07:35:33 EST
On Tuesday 29 August 2017 06:22 AM, kan.liang@xxxxxxxxx wrote:
From: Kan Liang <kan.liang@xxxxxxxxx>
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@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
---
This patch is kernel patch.
The user space patch can be found here.
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.spinics.net_lists_kernel_msg2587093.html&d=DwIBaQ&c=jf_iaSHvJObTbx-siA1ZOg&r=3f2W2m24mqGnx1C8qDsVjM_Sd89MwbaDB37IJVL-h7w&m=bL7qsJKf8aRpvBVr07ODZxoQhPgxffpGFgN9A4iyACw&s=R1OMYJt1szqNhPZu8QQDDRCnQgHZiQzcCPzofF6FIF8&e=
Changes since V7
- Fix virt_addr_valid compile warning for MIPS architecture (LKP)
arch/powerpc/perf/core-book3s.c | 3 ++-
arch/x86/events/intel/ds.c | 2 +-
arch/x86/events/perf_event.h | 2 +-
include/linux/perf_event.h | 2 ++
include/uapi/linux/perf_event.h | 4 +++-
kernel/events/core.c | 47 +++++++++++++++++++++++++++++++++++++++++
6 files changed, 56 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 6c2d416..2e3eb74 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -2039,7 +2039,8 @@ static void record_and_restart(struct perf_event *event, unsigned long val,
perf_sample_data_init(&data, ~0ULL, event->hw.last_period);
- if (event->attr.sample_type & PERF_SAMPLE_ADDR)
+ if (event->attr.sample_type &
+ (PERF_SAMPLE_ADDR | PERF_SAMPLE_PHYS_ADDR))
perf_get_data_addr(regs, &data.addr);
if (event->attr.sample_type & PERF_SAMPLE_BRANCH_STACK) {
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index a322fed..0516f78 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1175,7 +1175,7 @@ static void setup_pebs_sample_data(struct perf_event *event,
else
regs->flags &= ~PERF_EFLAGS_EXACT;
- if ((sample_type & PERF_SAMPLE_ADDR) &&
+ if ((sample_type & (PERF_SAMPLE_ADDR | PERF_SAMPLE_PHYS_ADDR)) &&
x86_pmu.intel_cap.pebs_format >= 1)
data->addr = pebs->dla;
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 476aec3..65bb91e 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -91,7 +91,7 @@ struct amd_nb {
(PERF_SAMPLE_IP | PERF_SAMPLE_TID | PERF_SAMPLE_ADDR | \
PERF_SAMPLE_ID | PERF_SAMPLE_CPU | PERF_SAMPLE_STREAM_ID | \
PERF_SAMPLE_DATA_SRC | PERF_SAMPLE_IDENTIFIER | \
- PERF_SAMPLE_TRANSACTION)
+ PERF_SAMPLE_TRANSACTION | PERF_SAMPLE_PHYS_ADDR)
/*
* A debug store configuration.
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index b14095b..74fb87e 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -944,6 +944,8 @@ struct perf_sample_data {
struct perf_regs regs_intr;
u64 stack_user_size;
+
+ u64 phys_addr;
} ____cacheline_aligned;
/* default value for data source */
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 642db5f..cbea02f 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -139,8 +139,9 @@ enum perf_event_sample_format {
PERF_SAMPLE_IDENTIFIER = 1U << 16,
PERF_SAMPLE_TRANSACTION = 1U << 17,
PERF_SAMPLE_REGS_INTR = 1U << 18,
+ PERF_SAMPLE_PHYS_ADDR = 1U << 19,
- PERF_SAMPLE_MAX = 1U << 19, /* non-ABI */
+ PERF_SAMPLE_MAX = 1U << 20, /* non-ABI */
};
/*
@@ -814,6 +815,7 @@ enum perf_event_type {
* { u64 transaction; } && PERF_SAMPLE_TRANSACTION
* { u64 abi; # enum perf_sample_regs_abi
* u64 regs[weight(mask)]; } && PERF_SAMPLE_REGS_INTR
+ * { u64 phys_addr;} && PERF_SAMPLE_PHYS_ADDR
* };
*/
PERF_RECORD_SAMPLE = 9,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index d704e23..e8d5c5d 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1570,6 +1570,9 @@ 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;
}
@@ -6012,6 +6015,9 @@ 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;
@@ -6027,6 +6033,38 @@ 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,
@@ -6145,6 +6183,9 @@ 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
@@ -9892,6 +9933,12 @@ SYSCALL_DEFINE5(perf_event_open,
return -EINVAL;
}
+ /* Only privileged users can get kernel 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;