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SubjectRe: [BUG] perf: arch_perf_out_copy_user default
On Wed, Oct 30, 2013 at 08:50:28PM +0100, Frederic Weisbecker wrote:
>
> Would it make sense to rather make copy_from_user_nmi() to use a return value
> pattern that is closer to those of the existing copy_from_user_*() ?

Yeah we can do that I suppose; copy_form_user_nmi() actually uses
__copy_from_user_inatomic() since about a week.

Something like so I suppose.. please check, I'm in fail mode.

It looks like DEFINE_OUTPUT_COPY() functions already returned the bytes
not copied, and all its users appear to indeed expect that.

---
arch/x86/kernel/cpu/perf_event.c | 4 ++--
arch/x86/kernel/cpu/perf_event_intel_ds.c | 2 +-
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 2 +-
arch/x86/lib/usercopy.c | 2 +-
arch/x86/oprofile/backtrace.c | 4 ++--
kernel/events/internal.h | 35 ++++++++++++++++++++++--------
6 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 94bf3010bb39..0fa7dbe756e6 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1998,7 +1998,7 @@ perf_callchain_user32(struct pt_regs *regs, struct perf_callchain_entry *entry)
frame.return_address = 0;

bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
- if (bytes != sizeof(frame))
+ if (bytes != 0)
break;

if (!valid_user_frame(fp, sizeof(frame)))
@@ -2050,7 +2050,7 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
frame.return_address = 0;

bytes = copy_from_user_nmi(&frame, fp, sizeof(frame));
- if (bytes != sizeof(frame))
+ if (bytes != 0)
break;

if (!valid_user_frame(fp, sizeof(frame)))
diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index c1760ff3c757..ae96cfa5eddd 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -789,7 +789,7 @@ static int intel_pmu_pebs_fixup_ip(struct pt_regs *regs)

size = ip - to; /* Must fit our buffer, see above */
bytes = copy_from_user_nmi(buf, (void __user *)to, size);
- if (bytes != size)
+ if (bytes != 0)
return 0;

kaddr = buf;
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index 90ee6c1d0542..d82d155aca8c 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -491,7 +491,7 @@ static int branch_type(unsigned long from, unsigned long to, int abort)

/* may fail if text not present */
bytes = copy_from_user_nmi(buf, (void __user *)from, size);
- if (bytes != size)
+ if (bytes != 0)
return X86_BR_NONE;

addr = buf;
diff --git a/arch/x86/lib/usercopy.c b/arch/x86/lib/usercopy.c
index 5465b8613944..ddf9ecb53cc3 100644
--- a/arch/x86/lib/usercopy.c
+++ b/arch/x86/lib/usercopy.c
@@ -31,6 +31,6 @@ copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
ret = __copy_from_user_inatomic(to, from, n);
pagefault_enable();

- return n - ret;
+ return ret;
}
EXPORT_SYMBOL_GPL(copy_from_user_nmi);
diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c
index d6aa6e8315d1..5d04be5efb64 100644
--- a/arch/x86/oprofile/backtrace.c
+++ b/arch/x86/oprofile/backtrace.c
@@ -47,7 +47,7 @@ dump_user_backtrace_32(struct stack_frame_ia32 *head)
unsigned long bytes;

bytes = copy_from_user_nmi(bufhead, head, sizeof(bufhead));
- if (bytes != sizeof(bufhead))
+ if (bytes != 0)
return NULL;

fp = (struct stack_frame_ia32 *) compat_ptr(bufhead[0].next_frame);
@@ -93,7 +93,7 @@ static struct stack_frame *dump_user_backtrace(struct stack_frame *head)
unsigned long bytes;

bytes = copy_from_user_nmi(bufhead, head, sizeof(bufhead));
- if (bytes != sizeof(bufhead))
+ if (bytes != 0)
return NULL;

oprofile_add_trace(bufhead[0].return_address);
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index ca6599723be5..569b218782ad 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -82,16 +82,16 @@ static inline unsigned long perf_data_size(struct ring_buffer *rb)
}

#define DEFINE_OUTPUT_COPY(func_name, memcpy_func) \
-static inline unsigned int \
+static inline unsigned long \
func_name(struct perf_output_handle *handle, \
- const void *buf, unsigned int len) \
+ const void *buf, unsigned long len) \
{ \
unsigned long size, written; \
\
do { \
- size = min_t(unsigned long, handle->size, len); \
- \
+ size = min(handle->size, len); \
written = memcpy_func(handle->addr, buf, size); \
+ written = size - written; \
\
len -= written; \
handle->addr += written; \
@@ -110,20 +110,37 @@ func_name(struct perf_output_handle *handle, \
return len; \
}

-static inline int memcpy_common(void *dst, const void *src, size_t n)
+static inline unsigned long
+memcpy_common(void *dst, const void *src, unsigned long n)
{
memcpy(dst, src, n);
- return n;
+ return 0;
}

DEFINE_OUTPUT_COPY(__output_copy, memcpy_common)

-#define MEMCPY_SKIP(dst, src, n) (n)
+static inline unsigned long
+memcpy_skip(void *dst, const void *src, unsigned long n)
+{
+ return 0;
+}

-DEFINE_OUTPUT_COPY(__output_skip, MEMCPY_SKIP)
+DEFINE_OUTPUT_COPY(__output_skip, memcpy_skip)

#ifndef arch_perf_out_copy_user
-#define arch_perf_out_copy_user __copy_from_user_inatomic
+#define arch_perf_out_copy_user arch_perf_out_copy_user
+
+static inline unsigned long
+arch_perf_out_copy_user(void *dst, const void *src, unsigned long n)
+{
+ unsigned long ret;
+
+ pagefault_disable();
+ ret = __copy_from_user_inatomic(dst, src, n);
+ pagefault_enable();
+
+ return ret;
+}
#endif

DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user)

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