From 2dddc7ef881669276c96356ec44c4e46ec20b1e9 Mon Sep 17 00:00:00 2001 From: Than McIntosh Date: Wed, 13 Mar 2024 19:03:43 +0000 Subject: [PATCH] cmd/link: move .dynamic and .got sections to relro if applicable This is the second of two CLs to roll forward the changes in CL 473495, which was subsequently reverted. In this patch we move the .dynamic and .got sections from the writable data segment to the relro segment if the platform supports relro and we're producing a PIE binary, and also moves .got.plt into relro if eager binding is in effect (e.g. -bindnow or -Wl,-z,now). Updates #45681. Change-Id: I9f4fba6e825b96d1b5e27fb75844450dd0a650b3 Reviewed-on: https://go-review.googlesource.com/c/go/+/571417 LUCI-TryBot-Result: Go LUCI Reviewed-by: Cherry Mui --- src/cmd/link/internal/ld/data.go | 3 +- src/cmd/link/internal/ld/elf.go | 20 ++++- src/cmd/link/internal/ld/elf_test.go | 58 +++++++++++++- src/cmd/link/internal/sym/symkind.go | 1 + src/cmd/link/internal/sym/symkind_string.go | 89 +++++++++++---------- 5 files changed, 121 insertions(+), 50 deletions(-) diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go index 11dc48b18b..feaa3c34d8 100644 --- a/src/cmd/link/internal/ld/data.go +++ b/src/cmd/link/internal/ld/data.go @@ -1850,7 +1850,7 @@ func (state *dodataState) allocateDataSections(ctxt *Link) { } ldr := ctxt.loader - // .got + // writable .got (note that for PIE binaries .got goes in relro) if len(state.data[sym.SELFGOT]) > 0 { state.allocateNamedSectionAndAssignSyms(&Segdata, ".got", sym.SELFGOT, sym.SDATA, 06) } @@ -2106,6 +2106,7 @@ func (state *dodataState) allocateDataSections(ctxt *Link) { xcoffUpdateOuterSize(ctxt, state.datsize-symnStartValue, symn) } } + state.assignToSection(sect, sym.SELFRELROSECT, sym.SRODATA) sect.Length = uint64(state.datsize) - sect.Vaddr } diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go index 97b24b0cae..0d8455d92e 100644 --- a/src/cmd/link/internal/ld/elf.go +++ b/src/cmd/link/internal/ld/elf.go @@ -1113,6 +1113,7 @@ func elfphload(seg *sym.Segment) *ElfPhdr { func elfphrelro(seg *sym.Segment) { ph := newElfPhdr() ph.Type = elf.PT_GNU_RELRO + ph.Flags = elf.PF_R ph.Vaddr = seg.Vaddr ph.Paddr = seg.Vaddr ph.Memsz = seg.Length @@ -1562,7 +1563,11 @@ func (ctxt *Link) doelf() { /* global offset table */ got := ldr.CreateSymForUpdate(".got", 0) - got.SetType(sym.SELFGOT) // writable + if ctxt.UseRelro() { + got.SetType(sym.SELFRELROSECT) + } else { + got.SetType(sym.SELFGOT) // writable + } /* ppc64 glink resolver */ if ctxt.IsPPC64() { @@ -1575,7 +1580,11 @@ func (ctxt *Link) doelf() { hash.SetType(sym.SELFROSECT) gotplt := ldr.CreateSymForUpdate(".got.plt", 0) - gotplt.SetType(sym.SELFSECT) // writable + if ctxt.UseRelro() && *flagBindNow { + gotplt.SetType(sym.SELFRELROSECT) + } else { + gotplt.SetType(sym.SELFSECT) // writable + } plt := ldr.CreateSymForUpdate(".plt", 0) if ctxt.IsPPC64() { @@ -1597,9 +1606,12 @@ func (ctxt *Link) doelf() { /* define dynamic elf table */ dynamic := ldr.CreateSymForUpdate(".dynamic", 0) - if thearch.ELF.DynamicReadOnly { + switch { + case thearch.ELF.DynamicReadOnly: dynamic.SetType(sym.SELFROSECT) - } else { + case ctxt.UseRelro(): + dynamic.SetType(sym.SELFRELROSECT) + default: dynamic.SetType(sym.SELFSECT) } diff --git a/src/cmd/link/internal/ld/elf_test.go b/src/cmd/link/internal/ld/elf_test.go index 16bf4039b1..b48cf66038 100644 --- a/src/cmd/link/internal/ld/elf_test.go +++ b/src/cmd/link/internal/ld/elf_test.go @@ -198,6 +198,7 @@ func TestElfBindNow(t *testing.T) { name string args []string prog string + wantSecsRO []string mustHaveBuildModePIE bool mustHaveCGO bool mustInternalLink bool @@ -213,6 +214,7 @@ func TestElfBindNow(t *testing.T) { mustHaveBuildModePIE: true, mustInternalLink: true, wantDf1Pie: true, + wantSecsRO: []string{".dynamic", ".got"}, }, { name: "bindnow-linkmode-internal", @@ -232,6 +234,7 @@ func TestElfBindNow(t *testing.T) { wantDfBindNow: true, wantDf1Now: true, wantDf1Pie: true, + wantSecsRO: []string{".dynamic", ".got", ".got.plt"}, }, { name: "bindnow-pie-linkmode-external", @@ -242,6 +245,8 @@ func TestElfBindNow(t *testing.T) { wantDfBindNow: true, wantDf1Now: true, wantDf1Pie: true, + // NB: external linker produces .plt.got, not .got.plt + wantSecsRO: []string{".dynamic", ".got"}, }, } @@ -251,10 +256,14 @@ func TestElfBindNow(t *testing.T) { return true } } - return false } + segContainsSec := func(p *elf.Prog, s *elf.Section) bool { + return s.Addr >= p.Vaddr && + s.Addr+s.FileSize <= p.Vaddr+p.Filesz + } + for _, test := range tests { t.Run(test.name, func(t *testing.T) { if test.mustInternalLink { @@ -329,6 +338,53 @@ func TestElfBindNow(t *testing.T) { if gotDf1Pie := gotDynFlag(flags1, uint64(elf.DF_1_PIE)); gotDf1Pie != test.wantDf1Pie { t.Fatalf("DT_FLAGS_1 DF_1_PIE got: %v, want: %v", gotDf1Pie, test.wantDf1Pie) } + + for _, wsroname := range test.wantSecsRO { + // Locate section of interest. + var wsro *elf.Section + for _, s := range elfFile.Sections { + if s.Name == wsroname { + wsro = s + break + } + } + if wsro == nil { + t.Fatalf("test %s: can't locate %q section", + test.name, wsroname) + } + + // Now walk the program headers. Section should be part of + // some segment that is readonly. + foundRO := false + foundSegs := []*elf.Prog{} + for _, p := range elfFile.Progs { + if segContainsSec(p, wsro) { + foundSegs = append(foundSegs, p) + if p.Flags == elf.PF_R { + foundRO = true + } + } + } + if !foundRO { + // Things went off the rails. Write out some + // useful information for a human looking at the + // test failure. + t.Logf("test %s: %q section not in readonly segment", + wsro.Name, test.name) + t.Logf("section %s location: st=0x%x en=0x%x\n", + wsro.Name, wsro.Addr, wsro.Addr+wsro.FileSize) + t.Logf("sec %s found in these segments: ", wsro.Name) + for _, p := range foundSegs { + t.Logf(" %q", p.Type) + } + t.Logf("\nall segments: \n") + for k, p := range elfFile.Progs { + t.Logf("%d t=%s fl=%s st=0x%x en=0x%x\n", + k, p.Type, p.Flags, p.Vaddr, p.Vaddr+p.Filesz) + } + t.Fatalf("test %s failed", test.name) + } + } }) } } diff --git a/src/cmd/link/internal/sym/symkind.go b/src/cmd/link/internal/sym/symkind.go index 08cafb206b..9a1f33c582 100644 --- a/src/cmd/link/internal/sym/symkind.go +++ b/src/cmd/link/internal/sym/symkind.go @@ -76,6 +76,7 @@ const ( SGCBITSRELRO SRODATARELRO SFUNCTABRELRO + SELFRELROSECT // Part of .data.rel.ro if it exists, otherwise part of .rodata. STYPELINK diff --git a/src/cmd/link/internal/sym/symkind_string.go b/src/cmd/link/internal/sym/symkind_string.go index 62b4fd92e5..b29c00334f 100644 --- a/src/cmd/link/internal/sym/symkind_string.go +++ b/src/cmd/link/internal/sym/symkind_string.go @@ -27,53 +27,54 @@ func _() { _ = x[SGCBITSRELRO-16] _ = x[SRODATARELRO-17] _ = x[SFUNCTABRELRO-18] - _ = x[STYPELINK-19] - _ = x[SITABLINK-20] - _ = x[SSYMTAB-21] - _ = x[SPCLNTAB-22] - _ = x[SFirstWritable-23] - _ = x[SBUILDINFO-24] - _ = x[SELFSECT-25] - _ = x[SMACHO-26] - _ = x[SMACHOGOT-27] - _ = x[SWINDOWS-28] - _ = x[SELFGOT-29] - _ = x[SNOPTRDATA-30] - _ = x[SINITARR-31] - _ = x[SDATA-32] - _ = x[SXCOFFTOC-33] - _ = x[SBSS-34] - _ = x[SNOPTRBSS-35] - _ = x[SLIBFUZZER_8BIT_COUNTER-36] - _ = x[SCOVERAGE_COUNTER-37] - _ = x[SCOVERAGE_AUXVAR-38] - _ = x[STLSBSS-39] - _ = x[SXREF-40] - _ = x[SMACHOSYMSTR-41] - _ = x[SMACHOSYMTAB-42] - _ = x[SMACHOINDIRECTPLT-43] - _ = x[SMACHOINDIRECTGOT-44] - _ = x[SFILEPATH-45] - _ = x[SDYNIMPORT-46] - _ = x[SHOSTOBJ-47] - _ = x[SUNDEFEXT-48] - _ = x[SDWARFSECT-49] - _ = x[SDWARFCUINFO-50] - _ = x[SDWARFCONST-51] - _ = x[SDWARFFCN-52] - _ = x[SDWARFABSFCN-53] - _ = x[SDWARFTYPE-54] - _ = x[SDWARFVAR-55] - _ = x[SDWARFRANGE-56] - _ = x[SDWARFLOC-57] - _ = x[SDWARFLINES-58] - _ = x[SSEHUNWINDINFO-59] - _ = x[SSEHSECT-60] + _ = x[SELFRELROSECT-19] + _ = x[STYPELINK-20] + _ = x[SITABLINK-21] + _ = x[SSYMTAB-22] + _ = x[SPCLNTAB-23] + _ = x[SFirstWritable-24] + _ = x[SBUILDINFO-25] + _ = x[SELFSECT-26] + _ = x[SMACHO-27] + _ = x[SMACHOGOT-28] + _ = x[SWINDOWS-29] + _ = x[SELFGOT-30] + _ = x[SNOPTRDATA-31] + _ = x[SINITARR-32] + _ = x[SDATA-33] + _ = x[SXCOFFTOC-34] + _ = x[SBSS-35] + _ = x[SNOPTRBSS-36] + _ = x[SLIBFUZZER_8BIT_COUNTER-37] + _ = x[SCOVERAGE_COUNTER-38] + _ = x[SCOVERAGE_AUXVAR-39] + _ = x[STLSBSS-40] + _ = x[SXREF-41] + _ = x[SMACHOSYMSTR-42] + _ = x[SMACHOSYMTAB-43] + _ = x[SMACHOINDIRECTPLT-44] + _ = x[SMACHOINDIRECTGOT-45] + _ = x[SFILEPATH-46] + _ = x[SDYNIMPORT-47] + _ = x[SHOSTOBJ-48] + _ = x[SUNDEFEXT-49] + _ = x[SDWARFSECT-50] + _ = x[SDWARFCUINFO-51] + _ = x[SDWARFCONST-52] + _ = x[SDWARFFCN-53] + _ = x[SDWARFABSFCN-54] + _ = x[SDWARFTYPE-55] + _ = x[SDWARFVAR-56] + _ = x[SDWARFRANGE-57] + _ = x[SDWARFLOC-58] + _ = x[SDWARFLINES-59] + _ = x[SSEHUNWINDINFO-60] + _ = x[SSEHSECT-61] } -const _SymKind_name = "SxxxSTEXTSELFRXSECTSMACHOPLTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSLIBFUZZER_8BIT_COUNTERSCOVERAGE_COUNTERSCOVERAGE_AUXVARSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSDYNIMPORTSHOSTOBJSUNDEFEXTSDWARFSECTSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINESSSEHUNWINDINFOSSEHSECT" +const _SymKind_name = "SxxxSTEXTSELFRXSECTSMACHOPLTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASFUNCTABSELFROSECTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSELFRELROSECTSTYPELINKSITABLINKSSYMTABSPCLNTABSFirstWritableSBUILDINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASINITARRSDATASXCOFFTOCSBSSSNOPTRBSSSLIBFUZZER_8BIT_COUNTERSCOVERAGE_COUNTERSCOVERAGE_AUXVARSTLSBSSSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSFILEPATHSDYNIMPORTSHOSTOBJSUNDEFEXTSDWARFSECTSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINESSSEHUNWINDINFOSSEHSECT" -var _SymKind_index = [...]uint16{0, 4, 9, 19, 28, 33, 40, 49, 56, 63, 70, 78, 88, 98, 110, 124, 136, 148, 160, 173, 182, 191, 198, 206, 220, 230, 238, 244, 253, 261, 268, 278, 286, 291, 300, 304, 313, 336, 353, 369, 376, 381, 393, 405, 422, 439, 448, 458, 466, 475, 485, 497, 508, 517, 529, 539, 548, 559, 568, 579, 593, 601} +var _SymKind_index = [...]uint16{0, 4, 9, 19, 28, 33, 40, 49, 56, 63, 70, 78, 88, 98, 110, 124, 136, 148, 160, 173, 186, 195, 204, 211, 219, 233, 243, 251, 257, 266, 274, 281, 291, 299, 304, 313, 317, 326, 349, 366, 382, 389, 394, 406, 418, 435, 452, 461, 471, 479, 488, 498, 510, 521, 530, 542, 552, 561, 572, 581, 592, 606, 614} func (i SymKind) String() string { if i >= SymKind(len(_SymKind_index)-1) {