cmd/link: move pclntab out of relro section

The .gopclntab section should not have any relocations.
Move it out of relro to regular rodata.

Note that this is tested by tests like TestNoTextrel in
cmd/cgo/internal/testshared.

The existing test TestMachoSectionsReadOnly looks for sections in a
Mach-O file that are read-only after relocations are applied
(this is marked by a segment with a flags field set to 0x10).
We remove the __gopclntab section, as that section is now read-only
at all times, not only after relocating.

For #76038

Change-Id: I7f837e423bf1e802509277f5dc7fdd1ed0228e32
Reviewed-on: https://go-review.googlesource.com/c/go/+/718065
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>

diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
index fcc327276079569a90ff7468d57678bfcd7acad9..e7e202fc1f638ef7fb748d16c62848cd960e40b0 100644 (file)
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -1581,7 +1581,7 @@ func (state *dodataState) makeRelroForSharedLib(target *Link) {
                                        // the relro data.
                                        isRelro = true
                                }
-                       case sym.SGOFUNC:
+                       case sym.SGOFUNC, sym.SPCLNTAB:
                                // The only SGOFUNC symbols that contain relocations are .stkobj,
                                // and their relocations are of type objabi.R_ADDROFF,
                                // which always get resolved during linking.
@@ -2119,6 +2119,21 @@ func (state *dodataState) allocateDataSections(ctxt *Link) {
                }
        }
 
+       /* gopclntab */
+       sect = state.allocateNamedSectionAndAssignSyms(segro, ".gopclntab", sym.SPCLNTAB, sym.SRODATA, 04)
+       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0), sect)
+       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pcheader", 0), sect)
+       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.funcnametab", 0), sect)
+       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.cutab", 0), sect)
+       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.filetab", 0), sect)
+       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pctab", 0), sect)
+       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.functab", 0), sect)
+       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.epclntab", 0), sect)
+       setCarrierSize(sym.SPCLNTAB, int64(sect.Length))
+       if ctxt.HeadType == objabi.Haix {
+               xcoffUpdateOuterSize(ctxt, int64(sect.Length), sym.SPCLNTAB)
+       }
+
        /* read-only ELF, Mach-O sections */
        state.allocateSingleSymSections(segro, sym.SELFROSECT, sym.SRODATA, 04)
 
@@ -2238,21 +2253,6 @@ func (state *dodataState) allocateDataSections(ctxt *Link) {
        state.checkdatsize(sym.SITABLINK)
        sect.Length = uint64(state.datsize) - sect.Vaddr
 
-       /* gopclntab */
-       sect = state.allocateNamedSectionAndAssignSyms(seg, genrelrosecname(".gopclntab"), sym.SPCLNTAB, sym.SRODATA, relroSecPerm)
-       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pclntab", 0), sect)
-       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pcheader", 0), sect)
-       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.funcnametab", 0), sect)
-       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.cutab", 0), sect)
-       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.filetab", 0), sect)
-       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.pctab", 0), sect)
-       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.functab", 0), sect)
-       ldr.SetSymSect(ldr.LookupOrCreateSym("runtime.epclntab", 0), sect)
-       setCarrierSize(sym.SPCLNTAB, int64(sect.Length))
-       if ctxt.HeadType == objabi.Haix {
-               xcoffUpdateOuterSize(ctxt, int64(sect.Length), sym.SPCLNTAB)
-       }
-
        // 6g uses 4-byte relocation offsets, so the entire segment must fit in 32 bits.
        if state.datsize != int64(uint32(state.datsize)) {
                Errorf("read-only data segment too large: %d", state.datsize)

diff --git a/src/cmd/link/internal/ld/elf.go b/src/cmd/link/internal/ld/elf.go
index 8981f1c3f02272c63c2a18eaa0cb3ba34fda854d..90f9388ed7410ceb794e076510a68da4fa527d15 100644 (file)
--- a/src/cmd/link/internal/ld/elf.go
+++ b/src/cmd/link/internal/ld/elf.go
@@ -1250,11 +1250,12 @@ func elfshbits(linkmode LinkMode, sect *sym.Section) *ElfShdr {
 
 func elfshreloc(arch *sys.Arch, sect *sym.Section) *ElfShdr {
        // If main section is SHT_NOBITS, nothing to relocate.
-       // Also nothing to relocate in .shstrtab or notes.
+       // Also nothing to relocate in .shstrtab or notes or .gopclntab.
        if sect.Vaddr >= sect.Seg.Vaddr+sect.Seg.Filelen {
                return nil
        }
-       if sect.Name == ".shstrtab" || sect.Name == ".tbss" {
+       switch sect.Name {
+       case ".shstrtab", ".tbss", ".gopclntab":
                return nil
        }
        if sect.Elfsect.(*ElfShdr).Type == uint32(elf.SHT_NOTE) {
@@ -1469,6 +1470,7 @@ func (ctxt *Link) doelf() {
        }
        shstrtabAddstring(".elfdata")
        shstrtabAddstring(".rodata")
+       shstrtabAddstring(".gopclntab")
        // See the comment about data.rel.ro.FOO section names in data.go.
        relro_prefix := ""
        if ctxt.UseRelro() {
@@ -1477,7 +1479,6 @@ func (ctxt *Link) doelf() {
        }
        shstrtabAddstring(relro_prefix + ".typelink")
        shstrtabAddstring(relro_prefix + ".itablink")
-       shstrtabAddstring(relro_prefix + ".gopclntab")
 
        if ctxt.IsExternal() {
                *FlagD = true
@@ -1486,7 +1487,6 @@ func (ctxt *Link) doelf() {
                shstrtabAddstring(elfRelType + ".rodata")
                shstrtabAddstring(elfRelType + relro_prefix + ".typelink")
                shstrtabAddstring(elfRelType + relro_prefix + ".itablink")
-               shstrtabAddstring(elfRelType + relro_prefix + ".gopclntab")
                shstrtabAddstring(elfRelType + ".noptrdata")
                shstrtabAddstring(elfRelType + ".data")
                if ctxt.UseRelro() {

diff --git a/src/cmd/link/internal/ld/elf_test.go b/src/cmd/link/internal/ld/elf_test.go
index c2a1bc0b9442e0534e3fabf1d21b4722a481b1df..c56d27f29e459d39fc60f47f099281149847394c 100644 (file)
--- a/src/cmd/link/internal/ld/elf_test.go
+++ b/src/cmd/link/internal/ld/elf_test.go
@@ -408,7 +408,7 @@ func TestElfBindNow(t *testing.T) {
 }
 
 // This program is intended to be just big/complicated enough that
-// we wind up with decent-sized .data.rel.ro.{typelink,itablink,gopclntab}
+// we wind up with decent-sized .data.rel.ro.{typelink,itablink}
 // sections.
 const ifacecallsProg = `
 package main

diff --git a/src/cmd/link/internal/ld/macho_test.go b/src/cmd/link/internal/ld/macho_test.go
index adf159ab6d2ce8eb8bc475d419f723a643adfbc9..905de67f6016ed13f672aeb6982b02b01dce423a 100644 (file)
--- a/src/cmd/link/internal/ld/macho_test.go
+++ b/src/cmd/link/internal/ld/macho_test.go
@@ -37,14 +37,14 @@ func TestMachoSectionsReadOnly(t *testing.T) {
                        args:             []string{"-ldflags", "-linkmode=internal"},
                        prog:             prog,
                        mustInternalLink: true,
-                       wantSecsRO:       []string{"__got", "__rodata", "__itablink", "__typelink", "__gopclntab"},
+                       wantSecsRO:       []string{"__got", "__rodata", "__itablink", "__typelink"},
                },
                {
                        name:        "linkmode-external",
                        args:        []string{"-ldflags", "-linkmode=external"},
                        prog:        prog,
                        mustHaveCGO: true,
-                       wantSecsRO:  []string{"__got", "__rodata", "__itablink", "__typelink", "__gopclntab"},
+                       wantSecsRO:  []string{"__got", "__rodata", "__itablink", "__typelink"},
                },
                {
                        name:             "cgo-linkmode-internal",
@@ -52,14 +52,14 @@ func TestMachoSectionsReadOnly(t *testing.T) {
                        prog:             progC,
                        mustHaveCGO:      true,
                        mustInternalLink: true,
-                       wantSecsRO:       []string{"__got", "__rodata", "__itablink", "__typelink", "__gopclntab"},
+                       wantSecsRO:       []string{"__got", "__rodata", "__itablink", "__typelink"},
                },
                {
                        name:        "cgo-linkmode-external",
                        args:        []string{"-ldflags", "-linkmode=external"},
                        prog:        progC,
                        mustHaveCGO: true,
-                       wantSecsRO:  []string{"__got", "__rodata", "__itablink", "__typelink", "__gopclntab"},
+                       wantSecsRO:  []string{"__got", "__rodata", "__itablink", "__typelink"},
                },
        }
 
@@ -111,7 +111,8 @@ func TestMachoSectionsReadOnly(t *testing.T) {
 
                        for _, wsroname := range test.wantSecsRO {
                                // Now walk the sections. Section should be part of
-                               // some segment that is readonly.
+                               // some segment that is made readonly after
+                               // relocations are appied.
                                var wsro *macho.Section
                                foundRO := false
                                for _, s := range machoFile.Sections {

diff --git a/src/cmd/link/internal/sym/symkind.go b/src/cmd/link/internal/sym/symkind.go
index 9f62e809e14ca32e070395b523717ee06326d042..8709e7b48f8a2a20085591540865386d3ba2b5cb 100644 (file)
--- a/src/cmd/link/internal/sym/symkind.go
+++ b/src/cmd/link/internal/sym/symkind.go
@@ -64,6 +64,7 @@ const (
        SRODATAFIPSEND   // End of FIPS read-only data.
        SRODATAEND       // End of read-only data.
        SFUNCTAB         // Appears to be unused, except for runtime.etypes.
+       SPCLNTAB         // Pclntab data.
        SELFROSECT       // ELF read-only data: relocs, dynamic linking info.
 
        // Read-only, non-executable, dynamically relocatable segment.
@@ -91,7 +92,6 @@ const (
 
        STYPELINK // Type links.
        SITABLINK // Itab links.
-       SPCLNTAB  // Pclntab data.
 
        // Allocated writable segment.
        SFirstWritable

diff --git a/src/cmd/link/internal/sym/symkind_string.go b/src/cmd/link/internal/sym/symkind_string.go
index 4e3a0a3431ae0b26bdba6ddf1b5c4aad90b516d6..019e7c746a679db5f6723bc5a20ac7a8ae872d21 100644 (file)
--- a/src/cmd/link/internal/sym/symkind_string.go
+++ b/src/cmd/link/internal/sym/symkind_string.go
@@ -27,19 +27,19 @@ func _() {
        _ = x[SRODATAFIPSEND-16]
        _ = x[SRODATAEND-17]
        _ = x[SFUNCTAB-18]
-       _ = x[SELFROSECT-19]
-       _ = x[STYPERELRO-20]
-       _ = x[SSTRINGRELRO-21]
-       _ = x[SGOSTRINGRELRO-22]
-       _ = x[SGOFUNCRELRO-23]
-       _ = x[SGCBITSRELRO-24]
-       _ = x[SRODATARELRO-25]
-       _ = x[SFUNCTABRELRO-26]
-       _ = x[SELFRELROSECT-27]
-       _ = x[SMACHORELROSECT-28]
-       _ = x[STYPELINK-29]
-       _ = x[SITABLINK-30]
-       _ = x[SPCLNTAB-31]
+       _ = x[SPCLNTAB-19]
+       _ = x[SELFROSECT-20]
+       _ = x[STYPERELRO-21]
+       _ = x[SSTRINGRELRO-22]
+       _ = x[SGOSTRINGRELRO-23]
+       _ = x[SGOFUNCRELRO-24]
+       _ = x[SGCBITSRELRO-25]
+       _ = x[SRODATARELRO-26]
+       _ = x[SFUNCTABRELRO-27]
+       _ = x[SELFRELROSECT-28]
+       _ = x[SMACHORELROSECT-29]
+       _ = x[STYPELINK-30]
+       _ = x[SITABLINK-31]
        _ = x[SFirstWritable-32]
        _ = x[SBUILDINFO-33]
        _ = x[SFIPSINFO-34]
@@ -90,9 +90,9 @@ func _() {
        _ = x[SSEHSECT-79]
 }
 
-const _SymKind_name = "SxxxSTEXTSTEXTFIPSSTARTSTEXTFIPSSTEXTFIPSENDSTEXTENDSELFRXSECTSMACHOPLTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASRODATAFIPSSTARTSRODATAFIPSSRODATAFIPSENDSRODATAENDSFUNCTABSELFROSECTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSELFRELROSECTSMACHORELROSECTSTYPELINKSITABLINKSPCLNTABSFirstWritableSBUILDINFOSFIPSINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASNOPTRDATAFIPSSTARTSNOPTRDATAFIPSSNOPTRDATAFIPSENDSNOPTRDATAENDSINITARRSDATASDATAFIPSSTARTSDATAFIPSSDATAFIPSENDSDATAENDSXCOFFTOCSBSSSNOPTRBSSSLIBFUZZER_8BIT_COUNTERSCOVERAGE_COUNTERSCOVERAGE_AUXVARSTLSBSSSFirstUnallocatedSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSDYNIMPORTSHOSTOBJSUNDEFEXTSDWARFSECTSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINESSDWARFADDRSSEHUNWINDINFOSSEHSECT"
+const _SymKind_name = "SxxxSTEXTSTEXTFIPSSTARTSTEXTFIPSSTEXTFIPSENDSTEXTENDSELFRXSECTSMACHOPLTSTYPESSTRINGSGOSTRINGSGOFUNCSGCBITSSRODATASRODATAFIPSSTARTSRODATAFIPSSRODATAFIPSENDSRODATAENDSFUNCTABSPCLNTABSELFROSECTSTYPERELROSSTRINGRELROSGOSTRINGRELROSGOFUNCRELROSGCBITSRELROSRODATARELROSFUNCTABRELROSELFRELROSECTSMACHORELROSECTSTYPELINKSITABLINKSFirstWritableSBUILDINFOSFIPSINFOSELFSECTSMACHOSMACHOGOTSWINDOWSSELFGOTSNOPTRDATASNOPTRDATAFIPSSTARTSNOPTRDATAFIPSSNOPTRDATAFIPSENDSNOPTRDATAENDSINITARRSDATASDATAFIPSSTARTSDATAFIPSSDATAFIPSENDSDATAENDSXCOFFTOCSBSSSNOPTRBSSSLIBFUZZER_8BIT_COUNTERSCOVERAGE_COUNTERSCOVERAGE_AUXVARSTLSBSSSFirstUnallocatedSXREFSMACHOSYMSTRSMACHOSYMTABSMACHOINDIRECTPLTSMACHOINDIRECTGOTSDYNIMPORTSHOSTOBJSUNDEFEXTSDWARFSECTSDWARFCUINFOSDWARFCONSTSDWARFFCNSDWARFABSFCNSDWARFTYPESDWARFVARSDWARFRANGESDWARFLOCSDWARFLINESSDWARFADDRSSEHUNWINDINFOSSEHSECT"
 
-var _SymKind_index = [...]uint16{0, 4, 9, 23, 32, 44, 52, 62, 71, 76, 83, 92, 99, 106, 113, 129, 140, 154, 164, 172, 182, 192, 204, 218, 230, 242, 254, 267, 280, 295, 304, 313, 321, 335, 345, 354, 362, 368, 377, 385, 392, 402, 421, 435, 452, 465, 473, 478, 492, 501, 513, 521, 530, 534, 543, 566, 583, 599, 606, 623, 628, 640, 652, 669, 686, 696, 704, 713, 723, 735, 746, 755, 767, 777, 786, 797, 806, 817, 827, 841, 849}
+var _SymKind_index = [...]uint16{0, 4, 9, 23, 32, 44, 52, 62, 71, 76, 83, 92, 99, 106, 113, 129, 140, 154, 164, 172, 180, 190, 200, 212, 226, 238, 250, 262, 275, 288, 303, 312, 321, 335, 345, 354, 362, 368, 377, 385, 392, 402, 421, 435, 452, 465, 473, 478, 492, 501, 513, 521, 530, 534, 543, 566, 583, 599, 606, 623, 628, 640, 652, 669, 686, 696, 704, 713, 723, 735, 746, 755, 767, 777, 786, 797, 806, 817, 827, 841, 849}
 
 func (i SymKind) String() string {
        if i >= SymKind(len(_SymKind_index)-1) {