@@ -11,20 +11,138 @@ import (
1111 "cmd/link/internal/ld"
1212 "cmd/link/internal/loader"
1313 "cmd/link/internal/sym"
14+ "debug/elf"
1415 "fmt"
1516 "log"
17+ "sort"
1618)
1719
20+ // fakeLabelName matches the RISCV_FAKE_LABEL_NAME from binutils.
21+ const fakeLabelName = ".L0 "
22+
1823func gentext (ctxt * ld.Link , ldr * loader.Loader ) {
1924}
2025
26+ func genSymsLate (ctxt * ld.Link , ldr * loader.Loader ) {
27+ if ctxt .LinkMode != ld .LinkExternal {
28+ return
29+ }
30+
31+ // Generate a local text symbol for each relocation target, as the
32+ // R_RISCV_PCREL_LO12_* relocations generated by elfreloc1 need it.
33+ if ctxt .Textp == nil {
34+ log .Fatal ("genSymsLate called before Textp has been assigned" )
35+ }
36+ var hi20Syms []loader.Sym
37+ for _ , s := range ctxt .Textp {
38+ relocs := ldr .Relocs (s )
39+ for ri := 0 ; ri < relocs .Count (); ri ++ {
40+ r := relocs .At (ri )
41+ if r .Type () != objabi .R_RISCV_PCREL_ITYPE && r .Type () != objabi .R_RISCV_PCREL_STYPE {
42+ continue
43+ }
44+ if r .Off () == 0 && ldr .SymType (s ) == sym .STEXT {
45+ // Use the symbol for the function instead of creating
46+ // an overlapping symbol.
47+ continue
48+ }
49+
50+ // TODO(jsing): Consider generating ELF symbols without needing
51+ // loader symbols, in order to reduce memory consumption. This
52+ // would require changes to genelfsym so that it called
53+ // putelfsym and putelfsyment as appropriate.
54+ sb := ldr .MakeSymbolBuilder (fakeLabelName )
55+ sb .SetType (sym .STEXT )
56+ sb .SetValue (ldr .SymValue (s ) + int64 (r .Off ()))
57+ sb .SetLocal (true )
58+ sb .SetReachable (true )
59+ sb .SetVisibilityHidden (true )
60+ sb .SetSect (ldr .SymSect (s ))
61+ if outer := ldr .OuterSym (s ); outer != 0 {
62+ ldr .AddInteriorSym (outer , sb .Sym ())
63+ }
64+ hi20Syms = append (hi20Syms , sb .Sym ())
65+ }
66+ }
67+ ctxt .Textp = append (ctxt .Textp , hi20Syms ... )
68+ ldr .SortSyms (ctxt .Textp )
69+ }
70+
71+ func findHI20Symbol (ctxt * ld.Link , ldr * loader.Loader , val int64 ) loader.Sym {
72+ idx := sort .Search (len (ctxt .Textp ), func (i int ) bool { return ldr .SymValue (ctxt .Textp [i ]) >= val })
73+ if idx >= len (ctxt .Textp ) {
74+ return 0
75+ }
76+ if s := ctxt .Textp [idx ]; ldr .SymValue (s ) == val && ldr .SymType (s ) == sym .STEXT {
77+ return s
78+ }
79+ return 0
80+ }
81+
2182func elfreloc1 (ctxt * ld.Link , out * ld.OutBuf , ldr * loader.Loader , s loader.Sym , r loader.ExtReloc , ri int , sectoff int64 ) bool {
22- log .Fatalf ("elfreloc1" )
23- return false
83+ elfsym := ld .ElfSymForReloc (ctxt , r .Xsym )
84+ switch r .Type {
85+ case objabi .R_ADDR , objabi .R_DWARFSECREF :
86+ out .Write64 (uint64 (sectoff ))
87+ switch r .Size {
88+ case 4 :
89+ out .Write64 (uint64 (elf .R_RISCV_32 ) | uint64 (elfsym )<< 32 )
90+ case 8 :
91+ out .Write64 (uint64 (elf .R_RISCV_64 ) | uint64 (elfsym )<< 32 )
92+ default :
93+ ld .Errorf (nil , "unknown size %d for %v relocation" , r .Size , r .Type )
94+ return false
95+ }
96+ out .Write64 (uint64 (r .Xadd ))
97+
98+ case objabi .R_CALLRISCV :
99+ // Call relocations are currently handled via R_RISCV_PCREL_ITYPE.
100+ // TODO(jsing): Consider generating elf.R_RISCV_CALL instead of a
101+ // HI20/LO12_I pair.
102+
103+ case objabi .R_RISCV_PCREL_ITYPE , objabi .R_RISCV_PCREL_STYPE :
104+ // Find the text symbol for the AUIPC instruction targeted
105+ // by this relocation.
106+ relocs := ldr .Relocs (s )
107+ offset := int64 (relocs .At (ri ).Off ())
108+ hi20Sym := findHI20Symbol (ctxt , ldr , ldr .SymValue (s )+ offset )
109+ if hi20Sym == 0 {
110+ ld .Errorf (nil , "failed to find text symbol for HI20 relocation at %d (%x)" , sectoff , ldr .SymValue (s )+ offset )
111+ return false
112+ }
113+ hi20ElfSym := ld .ElfSymForReloc (ctxt , hi20Sym )
114+
115+ // Emit two relocations - a R_RISCV_PCREL_HI20 relocation and a
116+ // corresponding R_RISCV_PCREL_LO12_I or R_RISCV_PCREL_LO12_S relocation.
117+ // Note that the LO12 relocation must point to a target that has a valid
118+ // HI20 PC-relative relocation text symbol, which in turn points to the
119+ // given symbol. For further details see the ELF specification for RISC-V:
120+ //
121+ // https://github.com/riscv/riscv-elf-psabi-doc/blob/master/riscv-elf.md#pc-relative-symbol-addresses
122+ //
123+ var hiRel , loRel elf.R_RISCV
124+ switch r .Type {
125+ case objabi .R_RISCV_PCREL_ITYPE :
126+ hiRel , loRel = elf .R_RISCV_PCREL_HI20 , elf .R_RISCV_PCREL_LO12_I
127+ case objabi .R_RISCV_PCREL_STYPE :
128+ hiRel , loRel = elf .R_RISCV_PCREL_HI20 , elf .R_RISCV_PCREL_LO12_S
129+ }
130+ out .Write64 (uint64 (sectoff ))
131+ out .Write64 (uint64 (hiRel ) | uint64 (elfsym )<< 32 )
132+ out .Write64 (uint64 (r .Xadd ))
133+ out .Write64 (uint64 (sectoff + 4 ))
134+ out .Write64 (uint64 (loRel ) | uint64 (hi20ElfSym )<< 32 )
135+ out .Write64 (uint64 (0 ))
136+
137+ default :
138+ return false
139+ }
140+
141+ return true
24142}
25143
26144func elfsetupplt (ctxt * ld.Link , plt , gotplt * loader.SymbolBuilder , dynamic loader.Sym ) {
27- log .Fatalf ("elfsetuplt " )
145+ log .Fatalf ("elfsetupplt " )
28146}
29147
30148func machoreloc1 (* sys.Arch , * ld.OutBuf , * loader.Loader , loader.Sym , loader.ExtReloc , int64 ) bool {
@@ -33,8 +151,20 @@ func machoreloc1(*sys.Arch, *ld.OutBuf, *loader.Loader, loader.Sym, loader.ExtRe
33151}
34152
35153func archreloc (target * ld.Target , ldr * loader.Loader , syms * ld.ArchSyms , r loader.Reloc , s loader.Sym , val int64 ) (o int64 , nExtReloc int , ok bool ) {
36- rs := r .Sym ()
37- rs = ldr .ResolveABIAlias (rs )
154+ if target .IsExternal () {
155+ switch r .Type () {
156+ case objabi .R_CALLRISCV :
157+ return val , 0 , true
158+
159+ case objabi .R_RISCV_PCREL_ITYPE , objabi .R_RISCV_PCREL_STYPE :
160+ return val , 2 , true
161+ }
162+
163+ return val , 0 , false
164+ }
165+
166+ rs := ldr .ResolveABIAlias (r .Sym ())
167+
38168 switch r .Type () {
39169 case objabi .R_CALLRISCV :
40170 // Nothing to do.
@@ -89,3 +219,11 @@ func archrelocvariant(*ld.Target, *loader.Loader, loader.Reloc, sym.RelocVariant
89219 log .Fatalf ("archrelocvariant" )
90220 return - 1
91221}
222+
223+ func extreloc (target * ld.Target , ldr * loader.Loader , r loader.Reloc , s loader.Sym ) (loader.ExtReloc , bool ) {
224+ switch r .Type () {
225+ case objabi .R_RISCV_PCREL_ITYPE , objabi .R_RISCV_PCREL_STYPE :
226+ return ld .ExtrelocViaOuterSym (ldr , r , s ), true
227+ }
228+ return loader.ExtReloc {}, false
229+ }
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