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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/default/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 int32
    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_CONST
    68  	R_PCREL
    69  	// R_TLS_LE, used on 386, amd64, and ARM, resolves to the offset of the
    70  	// thread-local symbol from the thread local base and is used to implement the
    71  	// "local exec" model for tls access (r.Sym is not set on intel platforms but is
    72  	// set to a TLS symbol -- runtime.tlsg -- in the linker when externally linking).
    73  	R_TLS_LE
    74  	// R_TLS_IE, used 386, amd64, and ARM resolves to the PC-relative offset to a GOT
    75  	// slot containing the offset from the thread-local symbol from the thread local
    76  	// base and is used to implemented the "initial exec" model for tls access (r.Sym
    77  	// is not set on intel platforms but is set to a TLS symbol -- runtime.tlsg -- in
    78  	// the linker when externally linking).
    79  	R_TLS_IE
    80  	R_GOTOFF
    81  	R_PLT0
    82  	R_PLT1
    83  	R_PLT2
    84  	R_USEFIELD
    85  	// R_USETYPE resolves to an *rtype, but no relocation is created. The
    86  	// linker uses this as a signal that the pointed-to type information
    87  	// should be linked into the final binary, even if there are no other
    88  	// direct references. (This is used for types reachable by reflection.)
    89  	R_USETYPE
    90  	// R_METHODOFF resolves to a 32-bit offset from the beginning of the section
    91  	// holding the data being relocated to the referenced symbol.
    92  	// It is a variant of R_ADDROFF used when linking from the uncommonType of a
    93  	// *rtype, and may be set to zero by the linker if it determines the method
    94  	// text is unreachable by the linked program.
    95  	R_METHODOFF
    96  	R_POWER_TOC
    97  	R_GOTPCREL
    98  	// R_JMPMIPS (only used on mips64) resolves to non-PC-relative target address
    99  	// of a JMP instruction, by encoding the address into the instruction.
   100  	// The stack nosplit check ignores this since it is not a function call.
   101  	R_JMPMIPS
   102  
   103  	// R_DWARFSECREF resolves to the offset of the symbol from its section.
   104  	// Target of relocation must be size 4 (in current implementation).
   105  	R_DWARFSECREF
   106  
   107  	// R_DWARFFILEREF resolves to an index into the DWARF .debug_line
   108  	// file table for the specified file symbol. Must be applied to an
   109  	// attribute of form DW_FORM_data4.
   110  	R_DWARFFILEREF
   111  
   112  	// Platform dependent relocations. Architectures with fixed width instructions
   113  	// have the inherent issue that a 32-bit (or 64-bit!) displacement cannot be
   114  	// stuffed into a 32-bit instruction, so an address needs to be spread across
   115  	// several instructions, and in turn this requires a sequence of relocations, each
   116  	// updating a part of an instruction. This leads to relocation codes that are
   117  	// inherently processor specific.
   118  
   119  	// Arm64.
   120  
   121  	// Set a MOV[NZ] immediate field to bits [15:0] of the offset from the thread
   122  	// local base to the thread local variable defined by the referenced (thread
   123  	// local) symbol. Error if the offset does not fit into 16 bits.
   124  	R_ARM64_TLS_LE
   125  
   126  	// Relocates an ADRP; LD64 instruction sequence to load the offset between
   127  	// the thread local base and the thread local variable defined by the
   128  	// referenced (thread local) symbol from the GOT.
   129  	R_ARM64_TLS_IE
   130  
   131  	// R_ARM64_GOTPCREL relocates an adrp, ld64 pair to compute the address of the GOT
   132  	// slot of the referenced symbol.
   133  	R_ARM64_GOTPCREL
   134  
   135  	// PPC64.
   136  
   137  	// R_POWER_TLS_LE is used to implement the "local exec" model for tls
   138  	// access. It resolves to the offset of the thread-local symbol from the
   139  	// thread pointer (R13) and inserts this value into the low 16 bits of an
   140  	// instruction word.
   141  	R_POWER_TLS_LE
   142  
   143  	// R_POWER_TLS_IE is used to implement the "initial exec" model for tls access. It
   144  	// relocates a D-form, DS-form instruction sequence like R_ADDRPOWER_DS. It
   145  	// inserts to the offset of GOT slot for the thread-local symbol from the TOC (the
   146  	// GOT slot is filled by the dynamic linker with the offset of the thread-local
   147  	// symbol from the thread pointer (R13)).
   148  	R_POWER_TLS_IE
   149  
   150  	// R_POWER_TLS marks an X-form instruction such as "MOVD 0(R13)(R31*1), g" as
   151  	// accessing a particular thread-local symbol. It does not affect code generation
   152  	// but is used by the system linker when relaxing "initial exec" model code to
   153  	// "local exec" model code.
   154  	R_POWER_TLS
   155  
   156  	// R_ADDRPOWER_DS is similar to R_ADDRPOWER above, but assumes the second
   157  	// instruction is a "DS-form" instruction, which has an immediate field occupying
   158  	// bits [15:2] of the instruction word. Bits [15:2] of the address of the
   159  	// relocated symbol are inserted into this field; it is an error if the last two
   160  	// bits of the address are not 0.
   161  	R_ADDRPOWER_DS
   162  
   163  	// R_ADDRPOWER_PCREL relocates a D-form, DS-form instruction sequence like
   164  	// R_ADDRPOWER_DS but inserts the offset of the GOT slot for the referenced symbol
   165  	// from the TOC rather than the symbol's address.
   166  	R_ADDRPOWER_GOT
   167  
   168  	// R_ADDRPOWER_PCREL relocates two D-form instructions like R_ADDRPOWER, but
   169  	// inserts the displacement from the place being relocated to the address of the
   170  	// the relocated symbol instead of just its address.
   171  	R_ADDRPOWER_PCREL
   172  
   173  	// R_ADDRPOWER_TOCREL relocates two D-form instructions like R_ADDRPOWER, but
   174  	// inserts the offset from the TOC to the address of the relocated symbol
   175  	// rather than the symbol's address.
   176  	R_ADDRPOWER_TOCREL
   177  
   178  	// R_ADDRPOWER_TOCREL relocates a D-form, DS-form instruction sequence like
   179  	// R_ADDRPOWER_DS but inserts the offset from the TOC to the address of the the
   180  	// relocated symbol rather than the symbol's address.
   181  	R_ADDRPOWER_TOCREL_DS
   182  
   183  	// R_PCRELDBL relocates s390x 2-byte aligned PC-relative addresses.
   184  	// TODO(mundaym): remove once variants can be serialized - see issue 14218.
   185  	R_PCRELDBL
   186  
   187  	// R_ADDRMIPSU (only used on mips/mips64) resolves to the sign-adjusted "upper" 16
   188  	// bits (bit 16-31) of an external address, by encoding it into the instruction.
   189  	R_ADDRMIPSU
   190  	// R_ADDRMIPSTLS (only used on mips64) resolves to the low 16 bits of a TLS
   191  	// address (offset from thread pointer), by encoding it into the instruction.
   192  	R_ADDRMIPSTLS
   193  	// R_ADDRCUOFF resolves to a pointer-sized offset from the start of the
   194  	// symbol's DWARF compile unit.
   195  	R_ADDRCUOFF
   196  )
   197  
   198  // IsDirectJump returns whether r is a relocation for a direct jump.
   199  // A direct jump is a CALL or JMP instruction that takes the target address
   200  // as immediate. The address is embedded into the instruction, possibly
   201  // with limited width.
   202  // An indirect jump is a CALL or JMP instruction that takes the target address
   203  // in register or memory.
   204  func (r RelocType) IsDirectJump() bool {
   205  	switch r {
   206  	case R_CALL, R_CALLARM, R_CALLARM64, R_CALLPOWER, R_CALLMIPS, R_JMPMIPS:
   207  		return true
   208  	}
   209  	return false
   210  }
   211  

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