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Source file src/cmd/internal/objabi/reloctype.go

Documentation: cmd/internal/objabi

     1  // Derived from Inferno utils/6l/l.h and related files.
     2  // https://bitbucket.org/inferno-os/inferno-os/src/master/utils/6l/l.h
     3  //
     4  //	Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
     5  //	Portions Copyright © 1995-1997 C H Forsyth (forsyth@terzarima.net)
     6  //	Portions Copyright © 1997-1999 Vita Nuova Limited
     7  //	Portions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com)
     8  //	Portions Copyright © 2004,2006 Bruce Ellis
     9  //	Portions Copyright © 2005-2007 C H Forsyth (forsyth@terzarima.net)
    10  //	Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
    11  //	Portions Copyright © 2009 The Go Authors. All rights reserved.
    12  //
    13  // Permission is hereby granted, free of charge, to any person obtaining a copy
    14  // of this software and associated documentation files (the "Software"), to deal
    15  // in the Software without restriction, including without limitation the rights
    16  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
    17  // copies of the Software, and to permit persons to whom the Software is
    18  // furnished to do so, subject to the following conditions:
    19  //
    20  // The above copyright notice and this permission notice shall be included in
    21  // all copies or substantial portions of the Software.
    22  //
    23  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    24  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    25  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
    26  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    27  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    28  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    29  // THE SOFTWARE.
    30  
    31  package objabi
    32  
    33  type RelocType int16
    34  
    35  //go:generate stringer -type=RelocType
    36  const (
    37  	R_ADDR RelocType = 1 + iota
    38  	// R_ADDRPOWER relocates a pair of "D-form" instructions (instructions with 16-bit
    39  	// immediates in the low half of the instruction word), usually addis followed by
    40  	// another add or a load, inserting the "high adjusted" 16 bits of the address of
    41  	// the referenced symbol into the immediate field of the first instruction and the
    42  	// low 16 bits into that of the second instruction.
    43  	R_ADDRPOWER
    44  	// R_ADDRARM64 relocates an adrp, add pair to compute the address of the
    45  	// referenced symbol.
    46  	R_ADDRARM64
    47  	// R_ADDRMIPS (only used on mips/mips64) resolves to the low 16 bits of an external
    48  	// address, by encoding it into the instruction.
    49  	R_ADDRMIPS
    50  	// R_ADDROFF resolves to a 32-bit offset from the beginning of the section
    51  	// holding the data being relocated to the referenced symbol.
    52  	R_ADDROFF
    53  	// R_WEAKADDROFF resolves just like R_ADDROFF but is a weak relocation.
    54  	// A weak relocation does not make the symbol it refers to reachable,
    55  	// and is only honored by the linker if the symbol is in some other way
    56  	// reachable.
    57  	R_WEAKADDROFF
    58  	R_SIZE
    59  	R_CALL
    60  	R_CALLARM
    61  	R_CALLARM64
    62  	R_CALLIND
    63  	R_CALLPOWER
    64  	// R_CALLMIPS (only used on mips64) resolves to non-PC-relative target address
    65  	// of a CALL (JAL) instruction, by encoding the address into the instruction.
    66  	R_CALLMIPS
    67  	// R_CALLRISCV marks RISC-V CALLs for stack checking.
    68  	R_CALLRISCV
    69  	R_CONST
    70  	R_PCREL
    71  	// R_TLS_LE, used on 386, amd64, and ARM, resolves to the offset of the
    72  	// thread-local symbol from the thread local base and is used to implement the
    73  	// "local exec" model for tls access (r.Sym is not set on intel platforms but is
    74  	// set to a TLS symbol -- runtime.tlsg -- in the linker when externally linking).
    75  	R_TLS_LE
    76  	// R_TLS_IE, used 386, amd64, and ARM resolves to the PC-relative offset to a GOT
    77  	// slot containing the offset from the thread-local symbol from the thread local
    78  	// base and is used to implemented the "initial exec" model for tls access (r.Sym
    79  	// is not set on intel platforms but is set to a TLS symbol -- runtime.tlsg -- in
    80  	// the linker when externally linking).
    81  	R_TLS_IE
    82  	R_GOTOFF
    83  	R_PLT0
    84  	R_PLT1
    85  	R_PLT2
    86  	R_USEFIELD
    87  	// R_USETYPE resolves to an *rtype, but no relocation is created. The
    88  	// linker uses this as a signal that the pointed-to type information
    89  	// should be linked into the final binary, even if there are no other
    90  	// direct references. (This is used for types reachable by reflection.)
    91  	R_USETYPE
    92  	// R_USEIFACE marks a type is converted to an interface in the function this
    93  	// relocation is applied to. The target is a type descriptor.
    94  	// This is a marker relocation (0-sized), for the linker's reachabililty
    95  	// analysis.
    96  	R_USEIFACE
    97  	// R_USEIFACEMETHOD marks an interface method that is used in the function
    98  	// this relocation is applied to. The target is an interface type descriptor.
    99  	// The addend is the offset of the method in the type descriptor.
   100  	// This is a marker relocation (0-sized), for the linker's reachabililty
   101  	// analysis.
   102  	R_USEIFACEMETHOD
   103  	// R_METHODOFF resolves to a 32-bit offset from the beginning of the section
   104  	// holding the data being relocated to the referenced symbol.
   105  	// It is a variant of R_ADDROFF used when linking from the uncommonType of a
   106  	// *rtype, and may be set to zero by the linker if it determines the method
   107  	// text is unreachable by the linked program.
   108  	R_METHODOFF
   109  	R_POWER_TOC
   110  	R_GOTPCREL
   111  	// R_JMPMIPS (only used on mips64) resolves to non-PC-relative target address
   112  	// of a JMP instruction, by encoding the address into the instruction.
   113  	// The stack nosplit check ignores this since it is not a function call.
   114  	R_JMPMIPS
   115  
   116  	// R_DWARFSECREF resolves to the offset of the symbol from its section.
   117  	// Target of relocation must be size 4 (in current implementation).
   118  	R_DWARFSECREF
   119  
   120  	// R_DWARFFILEREF resolves to an index into the DWARF .debug_line
   121  	// file table for the specified file symbol. Must be applied to an
   122  	// attribute of form DW_FORM_data4.
   123  	R_DWARFFILEREF
   124  
   125  	// Platform dependent relocations. Architectures with fixed width instructions
   126  	// have the inherent issue that a 32-bit (or 64-bit!) displacement cannot be
   127  	// stuffed into a 32-bit instruction, so an address needs to be spread across
   128  	// several instructions, and in turn this requires a sequence of relocations, each
   129  	// updating a part of an instruction. This leads to relocation codes that are
   130  	// inherently processor specific.
   131  
   132  	// Arm64.
   133  
   134  	// Set a MOV[NZ] immediate field to bits [15:0] of the offset from the thread
   135  	// local base to the thread local variable defined by the referenced (thread
   136  	// local) symbol. Error if the offset does not fit into 16 bits.
   137  	R_ARM64_TLS_LE
   138  
   139  	// Relocates an ADRP; LD64 instruction sequence to load the offset between
   140  	// the thread local base and the thread local variable defined by the
   141  	// referenced (thread local) symbol from the GOT.
   142  	R_ARM64_TLS_IE
   143  
   144  	// R_ARM64_GOTPCREL relocates an adrp, ld64 pair to compute the address of the GOT
   145  	// slot of the referenced symbol.
   146  	R_ARM64_GOTPCREL
   147  
   148  	// R_ARM64_GOT resolves a GOT-relative instruction sequence, usually an adrp
   149  	// followed by another ld instruction.
   150  	R_ARM64_GOT
   151  
   152  	// R_ARM64_PCREL resolves a PC-relative addresses instruction sequence, usually an
   153  	// adrp followed by another add instruction.
   154  	R_ARM64_PCREL
   155  
   156  	// R_ARM64_LDST8 sets a LD/ST immediate value to bits [11:0] of a local address.
   157  	R_ARM64_LDST8
   158  
   159  	// R_ARM64_LDST16 sets a LD/ST immediate value to bits [11:1] of a local address.
   160  	R_ARM64_LDST16
   161  
   162  	// R_ARM64_LDST32 sets a LD/ST immediate value to bits [11:2] of a local address.
   163  	R_ARM64_LDST32
   164  
   165  	// R_ARM64_LDST64 sets a LD/ST immediate value to bits [11:3] of a local address.
   166  	R_ARM64_LDST64
   167  
   168  	// R_ARM64_LDST128 sets a LD/ST immediate value to bits [11:4] of a local address.
   169  	R_ARM64_LDST128
   170  
   171  	// PPC64.
   172  
   173  	// R_POWER_TLS_LE is used to implement the "local exec" model for tls
   174  	// access. It resolves to the offset of the thread-local symbol from the
   175  	// thread pointer (R13) and inserts this value into the low 16 bits of an
   176  	// instruction word.
   177  	R_POWER_TLS_LE
   178  
   179  	// R_POWER_TLS_IE is used to implement the "initial exec" model for tls access. It
   180  	// relocates a D-form, DS-form instruction sequence like R_ADDRPOWER_DS. It
   181  	// inserts to the offset of GOT slot for the thread-local symbol from the TOC (the
   182  	// GOT slot is filled by the dynamic linker with the offset of the thread-local
   183  	// symbol from the thread pointer (R13)).
   184  	R_POWER_TLS_IE
   185  
   186  	// R_POWER_TLS marks an X-form instruction such as "MOVD 0(R13)(R31*1), g" as
   187  	// accessing a particular thread-local symbol. It does not affect code generation
   188  	// but is used by the system linker when relaxing "initial exec" model code to
   189  	// "local exec" model code.
   190  	R_POWER_TLS
   191  
   192  	// R_ADDRPOWER_DS is similar to R_ADDRPOWER above, but assumes the second
   193  	// instruction is a "DS-form" instruction, which has an immediate field occupying
   194  	// bits [15:2] of the instruction word. Bits [15:2] of the address of the
   195  	// relocated symbol are inserted into this field; it is an error if the last two
   196  	// bits of the address are not 0.
   197  	R_ADDRPOWER_DS
   198  
   199  	// R_ADDRPOWER_PCREL relocates a D-form, DS-form instruction sequence like
   200  	// R_ADDRPOWER_DS but inserts the offset of the GOT slot for the referenced symbol
   201  	// from the TOC rather than the symbol's address.
   202  	R_ADDRPOWER_GOT
   203  
   204  	// R_ADDRPOWER_PCREL relocates two D-form instructions like R_ADDRPOWER, but
   205  	// inserts the displacement from the place being relocated to the address of the
   206  	// relocated symbol instead of just its address.
   207  	R_ADDRPOWER_PCREL
   208  
   209  	// R_ADDRPOWER_TOCREL relocates two D-form instructions like R_ADDRPOWER, but
   210  	// inserts the offset from the TOC to the address of the relocated symbol
   211  	// rather than the symbol's address.
   212  	R_ADDRPOWER_TOCREL
   213  
   214  	// R_ADDRPOWER_TOCREL relocates a D-form, DS-form instruction sequence like
   215  	// R_ADDRPOWER_DS but inserts the offset from the TOC to the address of the
   216  	// relocated symbol rather than the symbol's address.
   217  	R_ADDRPOWER_TOCREL_DS
   218  
   219  	// RISC-V.
   220  
   221  	// R_RISCV_PCREL_ITYPE resolves a 32-bit PC-relative address using an
   222  	// AUIPC + I-type instruction pair.
   223  	R_RISCV_PCREL_ITYPE
   224  
   225  	// R_RISCV_PCREL_STYPE resolves a 32-bit PC-relative address using an
   226  	// AUIPC + S-type instruction pair.
   227  	R_RISCV_PCREL_STYPE
   228  
   229  	// R_RISCV_TLS_IE_ITYPE resolves a 32-bit TLS initial-exec TOC offset
   230  	// address using an AUIPC + I-type instruction pair.
   231  	R_RISCV_TLS_IE_ITYPE
   232  
   233  	// R_RISCV_TLS_IE_STYPE resolves a 32-bit TLS initial-exec TOC offset
   234  	// address using an AUIPC + S-type instruction pair.
   235  	R_RISCV_TLS_IE_STYPE
   236  
   237  	// R_PCRELDBL relocates s390x 2-byte aligned PC-relative addresses.
   238  	// TODO(mundaym): remove once variants can be serialized - see issue 14218.
   239  	R_PCRELDBL
   240  
   241  	// R_ADDRMIPSU (only used on mips/mips64) resolves to the sign-adjusted "upper" 16
   242  	// bits (bit 16-31) of an external address, by encoding it into the instruction.
   243  	R_ADDRMIPSU
   244  	// R_ADDRMIPSTLS (only used on mips64) resolves to the low 16 bits of a TLS
   245  	// address (offset from thread pointer), by encoding it into the instruction.
   246  	R_ADDRMIPSTLS
   247  
   248  	// R_ADDRCUOFF resolves to a pointer-sized offset from the start of the
   249  	// symbol's DWARF compile unit.
   250  	R_ADDRCUOFF
   251  
   252  	// R_WASMIMPORT resolves to the index of the WebAssembly function import.
   253  	R_WASMIMPORT
   254  
   255  	// R_XCOFFREF (only used on aix/ppc64) prevents garbage collection by ld
   256  	// of a symbol. This isn't a real relocation, it can be placed in anywhere
   257  	// in a symbol and target any symbols.
   258  	R_XCOFFREF
   259  )
   260  
   261  // IsDirectCall reports whether r is a relocation for a direct call.
   262  // A direct call is a CALL instruction that takes the target address
   263  // as an immediate. The address is embedded into the instruction, possibly
   264  // with limited width. An indirect call is a CALL instruction that takes
   265  // the target address in register or memory.
   266  func (r RelocType) IsDirectCall() bool {
   267  	switch r {
   268  	case R_CALL, R_CALLARM, R_CALLARM64, R_CALLMIPS, R_CALLPOWER, R_CALLRISCV:
   269  		return true
   270  	}
   271  	return false
   272  }
   273  
   274  // IsDirectJump reports whether r is a relocation for a direct jump.
   275  // A direct jump is a JMP instruction that takes the target address
   276  // as an immediate. The address is embedded into the instruction, possibly
   277  // with limited width. An indirect jump is a JMP instruction that takes
   278  // the target address in register or memory.
   279  func (r RelocType) IsDirectJump() bool {
   280  	switch r {
   281  	case R_JMPMIPS:
   282  		return true
   283  	}
   284  	return false
   285  }
   286  
   287  // IsDirectCallOrJump reports whether r is a relocation for a direct
   288  // call or a direct jump.
   289  func (r RelocType) IsDirectCallOrJump() bool {
   290  	return r.IsDirectCall() || r.IsDirectJump()
   291  }
   292  

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