diff options
Diffstat (limited to 'gas/doc/internals.texi')
| -rw-r--r-- | gas/doc/internals.texi | 106 |
1 files changed, 88 insertions, 18 deletions
diff --git a/gas/doc/internals.texi b/gas/doc/internals.texi index 6bd3277..647d273 100644 --- a/gas/doc/internals.texi +++ b/gas/doc/internals.texi @@ -1,6 +1,6 @@ \input texinfo @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, -@c 2001 +@c 2001, 2002 @c Free Software Foundation, Inc. @setfilename internals.info @node Top @@ -1250,18 +1250,94 @@ information removed. Depending upon the processing performed by @code{md_convert_frag} the frag information may or may not be necessary, as may the resolved values of the symbols. The default value is 1. -@item md_apply_fix3 -@cindex md_apply_fix3 -GAS will call this for each fixup. It should store the correct value in the -object file. @code{fixup_segment} performs a generic overflow check on the -@code{valueT *val} argument after @code{md_apply_fix3} returns. If the overflow -check is relevant for the target machine, then @code{md_apply_fix3} should -modify @code{valueT *val}, typically to the value stored in the object file. +@item TC_VALIDATE_FIX (@var{fixP}, @var{seg}, @var{skip}) +@cindex TC_VALIDATE_FIX +This macro is evaluated for each fixup (when @var{linkrelax} is not set). +It may be used to change the fixup in @code{struct fix *@var{fixP}} before +the generic code sees it, or to fully process the fixup. In the latter case, +a @code{goto @var{skip}} will bypass the generic code. -@item TC_HANDLES_FX_DONE -@cindex TC_HANDLES_FX_DONE -If this macro is defined, it means that @code{md_apply_fix3} correctly sets the -@code{fx_done} field in the fixup. +@item md_apply_fix3 (@var{fixP}, @var{valP}, @var{seg}) +@cindex md_apply_fix3 +GAS will call this for each fixup that passes the @code{TC_VALIDATE_FIX} test +when @var{linkrelax} is not set. It should store the correct value in the +object file. @code{struct fix *@var{fixP}} is the fixup @code{md_apply_fix3} +is operating on. @code{valueT *@var{valP}} is the value to store into the +object files, or at least is the generic code's best guess. Specifically, +*@var{valP} is the value of the fixup symbol, perhaps modified by +@code{MD_APPLY_SYM_VALUE}, plus @code{@var{fixP}->fx_offset} (symbol addend), +less @code{MD_PCREL_FROM_SECTION} for pc-relative fixups. +@code{segT @var{seg}} is the section the fix is in. +@code{fixup_segment} performs a generic overflow check on *@var{valP} after +@code{md_apply_fix3} returns. If the overflow check is relevant for the target +machine, then @code{md_apply_fix3} should modify *@var{valP}, typically to the +value stored in the object file. + +@item TC_FORCE_RELOCATION (@var{fix}) +@cindex TC_FORCE_RELOCATION +If this macro returns non-zero, it guarantees that a relocation will be emitted +even when the value can be resolved locally, as @code{fixup_segment} tries to +reduce the number of relocations emitted. For example, a fixup expression +against an absolute symbol will normally not require a reloc. If undefined, +a default of @w{@code{(S_FORCE_RELOC ((@var{fix})->fx_addsy))}} is used. + +@item TC_FORCE_RELOCATION_ABS (@var{fix}) +@cindex TC_FORCE_RELOCATION_ABS +Like @code{TC_FORCE_RELOCATION}, but used only for fixup expressions against an +absolute symbol. If undefined, @code{TC_FORCE_RELOCATION} will be used. + +@item TC_FORCE_RELOCATION_LOCAL (@var{fix}) +@cindex TC_FORCE_RELOCATION_LOCAL +Like @code{TC_FORCE_RELOCATION}, but used only for fixup expressions against a +symbol in the current section. If undefined, fixups that are not +@code{fx_pcrel} or @code{fx_plt} or for which @code{TC_FORCE_RELOCATION} +returns non-zero, will emit relocs. + +@item TC_FORCE_RELOCATION_SUB_SAME (@var{fix}, @var{seg}) +@cindex TC_FORCE_RELOCATION_SUB +This macro controls resolution of fixup expressions involving the +difference of two symbols in the same section. If this macro returns zero, +the subtrahend will be resolved and @code{fx_subsy} set to @code{NULL} for +@code{md_apply_fix3}. If undefined, the default of +@w{@code{! SEG_NORMAL (@var{seg})}} will be used. + +@item TC_FORCE_RELOCATION_SUB_ABS (@var{fix}) +@cindex TC_FORCE_RELOCATION_SUB_ABS +Like @code{TC_FORCE_RELOCATION_SUB_SAME}, but used when the subtrahend is an +absolute symbol. If the macro is undefined a default of +@w{@code{(S_FORCE_RELOC ((@var{fix})->fx_subsy))}} is used. + +@item TC_FORCE_RELOCATION_SUB_LOCAL (@var{fix}) +@cindex TC_FORCE_RELOCATION_SUB_LOCAL +Like @code{TC_FORCE_RELOCATION_SUB_ABS}, but the subtrahend is a symbol in the +same section as the fixup. + +@item TC_VALIDATE_FIX_SUB (@var{fix}) +@cindex TC_VALIDATE_FIX_SUB +This macro is evaluated for any fixup with a @code{fx_subsy} that +@code{fixup_segment} cannot reduce to a number. If the macro returns +@code{false} an error will be reported. + +@item MD_APPLY_SYM_VALUE (@var{fix}) +@cindex MD_APPLY_SYM_VALUE +This macro controls whether the symbol value becomes part of the value passed +to @code{md_apply_fix3}. If the macro is undefined, or returns non-zero, the +symbol value will be included. For ELF, a suitable definition might simply be +@code{0}, because ELF relocations don't include the symbol value in the addend. + +@item S_FORCE_RELOC (@var{sym}) +@cindex S_FORCE_RELOC +This macro (or function, for @code{BFD_ASSEMBLER} gas) returns true for symbols +that should not be reduced to section symbols or eliminated from expressions, +because they may be overridden by the linker. ie. for symbols that are +undefined, common or weak, or for ELF assemblers that support ELF shared +library linking semantics, global. + +@item EXTERN_FORCE_RELOC +@cindex EXTERN_FORCE_RELOC +This macro controls whether @code{S_FORCE_RELOC} returns true for global +symbols. If undefined, the default is @code{true} for ELF assemblers, and +@code{false} for non-ELF. @item tc_gen_reloc @cindex tc_gen_reloc @@ -1449,12 +1525,6 @@ You should define this macro to copy object format specific information from one symbol to another. GAS will call it when one symbol is equated to another. -@item obj_fix_adjustable -@cindex obj_fix_adjustable -You may define this macro to indicate whether a fixup against a locally defined -symbol should be adjusted to be against the section symbol. It should return a -non-zero value if the adjustment is acceptable. - @item obj_sec_sym_ok_for_reloc @cindex obj_sec_sym_ok_for_reloc You may define this macro to indicate that it is OK to use a section symbol in |