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perf_counter: Add forward/backward attribute ABI compatibility

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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>
This commit is contained in:
Peter Zijlstra
2009-06-12 12:46:55 +02:00
committed by Ingo Molnar
parent bbd36e5e6a
commit 974802eaa1
4 changed files with 105 additions and 10 deletions
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89
kernel/perf_counter.c
View File

@@ -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))