From 844485ec6aa2da15f203dda43b919f842c866750 Mon Sep 17 00:00:00 2001
From: Preston Van Loon <preston@prysmaticlabs.com>
Date: Tue, 17 Nov 2020 01:35:58 -0800
Subject: [PATCH] consensus/ethash: fix usage of *reflect.SliceHeader (#21372)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
* consensus/ethash: only use *reflect.SliceHeader, not reflect.SliceHeader. See comment here: https://github.com/golang/go/issues/40397\#issuecomment-663748689
* consensus/ethash: pr feedback from @mdempsky, makes a copy of dest such that is not mutated
* consensus/ethash: remove noop assign
* consensus/ethash: apply same fix to another location
Co-authored-by: Péter Szilágyi <peterke@gmail.com>
Co-authored-by: Martin Holst Swende <martin@swende.se>
---
consensus/ethash/algorithm.go | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/consensus/ethash/algorithm.go b/consensus/ethash/algorithm.go
index 47d7e51b5..80379597e 100644
--- a/consensus/ethash/algorithm.go
+++ b/consensus/ethash/algorithm.go
@@ -151,10 +151,12 @@ func generateCache(dest []uint32, epoch uint64, seed []byte) {
logFn("Generated ethash verification cache", "elapsed", common.PrettyDuration(elapsed))
}()
// Convert our destination slice to a byte buffer
- header := *(*reflect.SliceHeader)(unsafe.Pointer(&dest))
- header.Len *= 4
- header.Cap *= 4
- cache := *(*[]byte)(unsafe.Pointer(&header))
+ var cache []byte
+ cacheHdr := (*reflect.SliceHeader)(unsafe.Pointer(&cache))
+ dstHdr := (*reflect.SliceHeader)(unsafe.Pointer(&dest))
+ cacheHdr.Data = dstHdr.Data
+ cacheHdr.Len = dstHdr.Len * 4
+ cacheHdr.Cap = dstHdr.Cap * 4
// Calculate the number of theoretical rows (we'll store in one buffer nonetheless)
size := uint64(len(cache))
@@ -283,10 +285,12 @@ func generateDataset(dest []uint32, epoch uint64, cache []uint32) {
swapped := !isLittleEndian()
// Convert our destination slice to a byte buffer
- header := *(*reflect.SliceHeader)(unsafe.Pointer(&dest))
- header.Len *= 4
- header.Cap *= 4
- dataset := *(*[]byte)(unsafe.Pointer(&header))
+ var dataset []byte
+ datasetHdr := (*reflect.SliceHeader)(unsafe.Pointer(&dataset))
+ destHdr := (*reflect.SliceHeader)(unsafe.Pointer(&dest))
+ datasetHdr.Data = destHdr.Data
+ datasetHdr.Len = destHdr.Len * 4
+ datasetHdr.Cap = destHdr.Cap * 4
// Generate the dataset on many goroutines since it takes a while
threads := runtime.NumCPU()
--
GitLab