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fix(z): Address inconsistent mremap return arguments with arm64 (#309)
This PR adds a specific arm64 implementation for the `mremap` function which ignores the second return argument from the syscall. **All other Linux implementations are unchanged.** This PR reworks [an earlier PR](#281) so that the functionality on non-arm64 platforms remains the same. Tested on Linux amd64 and Linux arm64.
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,56 @@ | ||
// +build !arm64 | ||
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/* | ||
* Copyright 2020 Dgraph Labs, Inc. and Contributors | ||
* | ||
* Licensed under the Apache License, Version 2.0 (the "License"); | ||
* you may not use this file except in compliance with the License. | ||
* You may obtain a copy of the License at | ||
* | ||
* http://www.apache.org/licenses/LICENSE-2.0 | ||
* | ||
* Unless required by applicable law or agreed to in writing, software | ||
* distributed under the License is distributed on an "AS IS" BASIS, | ||
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
* See the License for the specific language governing permissions and | ||
* limitations under the License. | ||
*/ | ||
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package z | ||
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import ( | ||
"fmt" | ||
"reflect" | ||
"unsafe" | ||
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"golang.org/x/sys/unix" | ||
) | ||
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// mremap is a Linux-specific system call to remap pages in memory. This can be used in place of munmap + mmap. | ||
func mremap(data []byte, size int) ([]byte, error) { | ||
//nolint:lll | ||
// taken from <https://github.com/torvalds/linux/blob/f8394f232b1eab649ce2df5c5f15b0e528c92091/include/uapi/linux/mman.h#L8> | ||
const MREMAP_MAYMOVE = 0x1 | ||
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header := (*reflect.SliceHeader)(unsafe.Pointer(&data)) | ||
mmapAddr, mmapSize, errno := unix.Syscall6( | ||
unix.SYS_MREMAP, | ||
header.Data, | ||
uintptr(header.Len), | ||
uintptr(size), | ||
uintptr(MREMAP_MAYMOVE), | ||
0, | ||
0, | ||
) | ||
if errno != 0 { | ||
return nil, errno | ||
} | ||
if mmapSize != uintptr(size) { | ||
return nil, fmt.Errorf("mremap size mismatch: requested: %d got: %d", size, mmapSize) | ||
} | ||
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header.Data = mmapAddr | ||
header.Cap = size | ||
header.Len = size | ||
return data, nil | ||
} |
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@@ -0,0 +1,52 @@ | ||
/* | ||
* Copyright 2020 Dgraph Labs, Inc. and Contributors | ||
* | ||
* Licensed under the Apache License, Version 2.0 (the "License"); | ||
* you may not use this file except in compliance with the License. | ||
* You may obtain a copy of the License at | ||
* | ||
* http://www.apache.org/licenses/LICENSE-2.0 | ||
* | ||
* Unless required by applicable law or agreed to in writing, software | ||
* distributed under the License is distributed on an "AS IS" BASIS, | ||
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
* See the License for the specific language governing permissions and | ||
* limitations under the License. | ||
*/ | ||
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package z | ||
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import ( | ||
"reflect" | ||
"unsafe" | ||
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"golang.org/x/sys/unix" | ||
) | ||
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// mremap is a Linux-specific system call to remap pages in memory. This can be used in place of munmap + mmap. | ||
func mremap(data []byte, size int) ([]byte, error) { | ||
//nolint:lll | ||
// taken from <https://github.com/torvalds/linux/blob/f8394f232b1eab649ce2df5c5f15b0e528c92091/include/uapi/linux/mman.h#L8> | ||
const MREMAP_MAYMOVE = 0x1 | ||
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header := (*reflect.SliceHeader)(unsafe.Pointer(&data)) | ||
// For ARM64, the second return argument for SYS_MREMAP is inconsistent (prior allocated size) with | ||
// other architectures, which return the size allocated | ||
mmapAddr, _, errno := unix.Syscall6( | ||
unix.SYS_MREMAP, | ||
header.Data, | ||
uintptr(header.Len), | ||
uintptr(size), | ||
uintptr(MREMAP_MAYMOVE), | ||
0, | ||
0, | ||
) | ||
if errno != 0 { | ||
return nil, errno | ||
} | ||
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header.Data = mmapAddr | ||
header.Cap = size | ||
header.Len = size | ||
return data, nil | ||
} |