diff options
Diffstat (limited to 'src/runtime')
| -rw-r--r-- | src/runtime/mgcmark.go | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go index 2c63724472..645083db07 100644 --- a/src/runtime/mgcmark.go +++ b/src/runtime/mgcmark.go @@ -237,14 +237,18 @@ func markrootBlock(b0, n0 uintptr, ptrmask0 *uint8, gcw *gcWork, shard int) { throw("rootBlockBytes must be a multiple of 8*ptrSize") } - b := b0 + uintptr(shard)*rootBlockBytes - if b >= b0+n0 { + // Note that if b0 is toward the end of the address space, + // then b0 + rootBlockBytes might wrap around. + // These tests are written to avoid any possible overflow. + off := uintptr(shard) * rootBlockBytes + if off >= n0 { return } + b := b0 + off ptrmask := (*uint8)(add(unsafe.Pointer(ptrmask0), uintptr(shard)*(rootBlockBytes/(8*sys.PtrSize)))) n := uintptr(rootBlockBytes) - if b+n > b0+n0 { - n = b0 + n0 - b + if off+n > n0 { + n = n0 - off } // Scan this shard. |