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Subject[PATCH] perf: Fix arch_perf_out_copy_user default implementation
Subject: perf: Fix arch_perf_out_copy_user default implementation

I noticed that the arch_perf_output_copy_user default of
__copy_from_user_inatomic has different return semantics that all other
memcpy functions we use -- notably also copy_from_user_nmi() for x86.

So provide a compatible default function.

Also change all the memcpy functions to use unsigned long.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
---
kernel/events/internal.h | 31 ++++++++++++++++++++++++-------
1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index ca6599723be5..325e85776406 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -82,14 +82,14 @@ 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); \
\
@@ -110,7 +110,8 @@ 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;
@@ -118,12 +119,28 @@ static inline int memcpy_common(void *dst, const void *src, size_t n)

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 n;
+}

-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 n - ret;
+}
#endif

DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user)

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