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[dev.link] cmd/internal/obj: handle content-addressable symbols with …
…relocations For content-addressable symbols with relocations, we build a content hash based on its content and relocations. Depending on the category of the referenced symbol, we choose different hash algorithms such that the hash is globally consistent. For now, we only support content-addressable symbols with relocations when the current package's import path is known, so that the symbol names are fully expanded. Otherwise, if the referenced symbol is a named symbol whose name is not fully expanded, the hash won't be globally consistent, and can cause erroneous collisions. This is fine for now, as the deduplication is just an optimization, not a requirement for correctness (until we get to type descriptors). Change-Id: I639e4e03dd749b5d71f0a55c2525926575b1ac30 Reviewed-on: https://go-review.googlesource.com/c/go/+/243142 Run-TryBot: Cherry Zhang <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Jeremy Faller <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,87 @@ | ||
| // Copyright 2020 The Go Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
|
|
||
| package obj | ||
|
|
||
| import ( | ||
| "cmd/internal/goobj2" | ||
| "cmd/internal/sys" | ||
| "testing" | ||
| ) | ||
|
|
||
| var dummyArch = LinkArch{Arch: sys.ArchAMD64} | ||
|
|
||
| func TestContentHash64(t *testing.T) { | ||
| s1 := &LSym{P: []byte("A")} | ||
| s2 := &LSym{P: []byte("A\x00\x00\x00")} | ||
| s1.Set(AttrContentAddressable, true) | ||
| s2.Set(AttrContentAddressable, true) | ||
| h1 := contentHash64(s1) | ||
| h2 := contentHash64(s2) | ||
| if h1 != h2 { | ||
| t.Errorf("contentHash64(s1)=%x, contentHash64(s2)=%x, expect equal", h1, h2) | ||
| } | ||
|
|
||
| ctxt := Linknew(&dummyArch) // little endian | ||
| s3 := ctxt.Int64Sym(int64('A')) | ||
| h3 := contentHash64(s3) | ||
| if h1 != h3 { | ||
| t.Errorf("contentHash64(s1)=%x, contentHash64(s3)=%x, expect equal", h1, h3) | ||
| } | ||
| } | ||
|
|
||
| func TestContentHash(t *testing.T) { | ||
| syms := []*LSym{ | ||
| &LSym{P: []byte("TestSymbol")}, // 0 | ||
| &LSym{P: []byte("TestSymbol")}, // 1 | ||
| &LSym{P: []byte("TestSymbol2")}, // 2 | ||
| &LSym{P: []byte("")}, // 3 | ||
| &LSym{P: []byte("")}, // 4 | ||
| &LSym{P: []byte("")}, // 5 | ||
| &LSym{P: []byte("")}, // 6 | ||
| } | ||
| for _, s := range syms { | ||
| s.Set(AttrContentAddressable, true) | ||
| s.PkgIdx = goobj2.PkgIdxHashed | ||
| } | ||
| // s3 references s0 | ||
| r := Addrel(syms[3]) | ||
| r.Sym = syms[0] | ||
| // s4 references s0 | ||
| r = Addrel(syms[4]) | ||
| r.Sym = syms[0] | ||
| // s5 references s1 | ||
| r = Addrel(syms[5]) | ||
| r.Sym = syms[1] | ||
| // s6 references s2 | ||
| r = Addrel(syms[6]) | ||
| r.Sym = syms[2] | ||
|
|
||
| // compute hashes | ||
| h := make([]goobj2.HashType, len(syms)) | ||
| w := &writer{} | ||
| for i := range h { | ||
| h[i] = w.contentHash(syms[i]) | ||
| } | ||
|
|
||
| tests := []struct { | ||
| a, b int | ||
| equal bool | ||
| }{ | ||
| {0, 1, true}, // same contents, no relocs | ||
| {0, 2, false}, // different contents | ||
| {3, 4, true}, // same contents, same relocs | ||
| {3, 5, true}, // recursively same contents | ||
| {3, 6, false}, // same contents, different relocs | ||
| } | ||
| for _, test := range tests { | ||
| if (h[test.a] == h[test.b]) != test.equal { | ||
| eq := "equal" | ||
| if !test.equal { | ||
| eq = "not equal" | ||
| } | ||
| t.Errorf("h%d=%x, h%d=%x, expect %s", test.a, h[test.a], test.b, h[test.b], eq) | ||
| } | ||
| } | ||
| } |
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