[tip:perfcounters/core] perf_counter: Add forward/backward attribute ABI compatibility

tip-bot for Peter Zijlstra
2009-06-12T12:44:22Z

Commit-ID: 974802eaa1afdc87e00821df7020a2b3c6fee623
Gitweb: http://git.kernel.org/tip/974802eaa1afdc87e00821df7020a2b3c6fee623
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Fri, 12 Jun 2009 12:46:55 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 12 Jun 2009 14:28:52 +0200

perf_counter: Add forward/backward attribute ABI compatibility

Provide for means of extending the perf_counter_attr in a 'natural' way.

We allow growing the structure by appending fields at the end by specifying
the full structure size inside it.

When a new kernel sees a smaller (old) structure, it will 0 pad the tail.
When an old kernel sees a larger (new) structure, it will verify the tail
consists of 0s, otherwise fail.

If we fail due to a size-mismatch, we return -E2BIG and write the kernel's
native attribe size back into the provided structure.

Furthermore, add some attribute verification, so that we'll fail counter
creation when unknown bits are present (PERF_SAMPLE, PERF_FORMAT, or in
the __reserved fields).

(This ABI detail is introduced while keeping the existing syscall ABI.)

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
include/linux/perf_counter.h | 19 +++++++--
include/linux/syscalls.h | 2 +-
kernel/perf_counter.c | 89 ++++++++++++++++++++++++++++++++++++++++-
tools/perf/perf.h | 5 +-
4 files changed, 105 insertions(+), 10 deletions(-)

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 7c4f32f..1b3118a 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -120,6 +120,8 @@ enum perf_counter_sample_format {
PERF_SAMPLE_ID = 1U << 6,
PERF_SAMPLE_CPU = 1U << 7,
PERF_SAMPLE_PERIOD = 1U << 8,
+
+ PERF_SAMPLE_MAX = 1U << 9, /* non-ABI */
};

/*
@@ -131,17 +133,26 @@ enum perf_counter_read_format {
PERF_FORMAT_TOTAL_TIME_ENABLED = 1U << 0,
PERF_FORMAT_TOTAL_TIME_RUNNING = 1U << 1,
PERF_FORMAT_ID = 1U << 2,
+
+ PERF_FORMAT_MAX = 1U << 3, /* non-ABI */
};

+#define PERF_ATTR_SIZE_VER0 64 /* sizeof first published struct */
+
/*
* Hardware event to monitor via a performance monitoring counter:
*/
struct perf_counter_attr {
+
/*
* Major type: hardware/software/tracepoint/etc.
*/
__u32 type;
- __u32 __reserved_1;
+
+ /*
+ * Size of the attr structure, for fwd/bwd compat.
+ */
+ __u32 size;

/*
* Type specific configuration information.
@@ -168,12 +179,12 @@ struct perf_counter_attr {
comm : 1, /* include comm data */
freq : 1, /* use freq, not period */

- __reserved_2 : 53;
+ __reserved_1 : 53;

__u32 wakeup_events; /* wakeup every n events */
- __u32 __reserved_3;
+ __u32 __reserved_2;

- __u64 __reserved_4;
+ __u64 __reserved_3;
};

/*
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index c6c84ad..418d90f 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -758,6 +758,6 @@ int kernel_execve(const char *filename, char *const argv[], char *const envp[]);

asmlinkage long sys_perf_counter_open(
- const struct perf_counter_attr __user *attr_uptr,
+ struct perf_counter_attr __user *attr_uptr,
pid_t pid, int cpu, int group_fd, unsigned long flags);
#endif
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 663bbe0..29b685f 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -3584,6 +3584,9 @@ perf_counter_alloc(struct perf_counter_attr *attr,
case PERF_TYPE_TRACEPOINT:
pmu = tp_perf_counter_init(counter);
break;
+
+ default:
+ break;
}
done:
err = 0;
@@ -3610,6 +3613,85 @@ done:
return counter;
}

+static int perf_copy_attr(struct perf_counter_attr __user *uattr,
+ struct perf_counter_attr *attr)
+{
+ int ret;
+ u32 size;
+
+ if (!access_ok(VERIFY_WRITE, uattr, PERF_ATTR_SIZE_VER0))
+ return -EFAULT;
+
+ /*
+ * zero the full structure, so that a short copy will be nice.
+ */
+ memset(attr, 0, sizeof(*attr));
+
+ ret = get_user(size, &uattr->size);
+ if (ret)
+ return ret;
+
+ if (size > PAGE_SIZE) /* silly large */
+ goto err_size;
+
+ if (!size) /* abi compat */
+ size = PERF_ATTR_SIZE_VER0;
+
+ if (size < PERF_ATTR_SIZE_VER0)
+ goto err_size;
+
+ /*
+ * If we're handed a bigger struct than we know of,
+ * ensure all the unknown bits are 0.
+ */
+ if (size > sizeof(*attr)) {
+ unsigned long val;
+ unsigned long __user *addr;
+ unsigned long __user *end;
+
+ addr = PTR_ALIGN((void __user *)uattr + sizeof(*attr),
+ sizeof(unsigned long));
+ end = PTR_ALIGN((void __user *)uattr + size,
+ sizeof(unsigned long));
+
+ for (; addr < end; addr += sizeof(unsigned long)) {
+ ret = get_user(val, addr);
+ if (ret)
+ return ret;
+ if (val)
+ goto err_size;
+ }
+ }
+
+ ret = copy_from_user(attr, uattr, size);
+ if (ret)
+ return -EFAULT;
+
+ /*
+ * If the type exists, the corresponding creation will verify
+ * the attr->config.
+ */
+ if (attr->type >= PERF_TYPE_MAX)
+ return -EINVAL;
+
+ if (attr->__reserved_1 || attr->__reserved_2 || attr->__reserved_3)
+ return -EINVAL;
+
+ if (attr->sample_type & ~(PERF_SAMPLE_MAX-1))
+ return -EINVAL;
+
+ if (attr->read_format & ~(PERF_FORMAT_MAX-1))
+ return -EINVAL;
+
+out:
+ return ret;
+
+err_size:
+ put_user(sizeof(*attr), &uattr->size);
+ ret = -E2BIG;
+ goto out;
+}
+
/**
* sys_perf_counter_open - open a performance counter, associate it to a task/cpu
*
@@ -3619,7 +3701,7 @@ done:
* @group_fd: group leader counter fd
*/
SYSCALL_DEFINE5(perf_counter_open,
- const struct perf_counter_attr __user *, attr_uptr,
+ struct perf_counter_attr __user *, attr_uptr,
pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
{
struct perf_counter *counter, *group_leader;
@@ -3635,8 +3717,9 @@ SYSCALL_DEFINE5(perf_counter_open,
if (flags)
return -EINVAL;

- if (copy_from_user(&attr, attr_uptr, sizeof(attr)) != 0)
- return -EFAULT;
+ ret = perf_copy_attr(attr_uptr, &attr);
+ if (ret)
+ return ret;

if (!attr.exclude_kernel) {
if (perf_paranoid_kernel() && !capable(CAP_SYS_ADMIN))
diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index af0a504..87a1aca 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -53,11 +53,12 @@ static inline unsigned long long rdclock(void)
_min1 < _min2 ? _min1 : _min2; })

static inline int
-sys_perf_counter_open(struct perf_counter_attr *attr_uptr,
+sys_perf_counter_open(struct perf_counter_attr *attr,
pid_t pid, int cpu, int group_fd,
unsigned long flags)
{
- return syscall(__NR_perf_counter_open, attr_uptr, pid, cpu,
+ attr->size = sizeof(*attr);
+ return syscall(__NR_perf_counter_open, attr, pid, cpu,
group_fd, flags);
}