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cmd/link: improve comments for relocsym

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This patch contains the remnants of CL (122482), which was intended to
reduce memory allocation in 'relocsym'. Another CL (113637) went in
first that included pretty much all of the code changes in 122482,
however there are some changes to comments that are worth preserving.

Change-Id: Iacdbd2bfe3b7ca2656596570f06ce9a646211913
Reviewed-on: https://go-review.googlesource.com/122482
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Than McIntosh 2018-07-06 12:45:03 -04:00
parent 21e85c293d
commit c7271c0c25
2 changed files with 55 additions and 23 deletions
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15
src/cmd/link/internal/ld/data.go
View File

@ -111,7 +111,20 @@ func trampoline(ctxt *Link, s *sym.Symbol) {
} }
// resolve relocations in s. // relocsym resolve relocations in "s". The main loop walks through
// the list of relocations attached to "s" and resolves them where
// applicable. Relocations are often architecture-specific, requiring
// calls into the 'archreloc' and/or 'archrelocvariant' functions for
// the architecture. When external linking is in effect, it may not be
// possible to completely resolve the address/offset for a symbol, in
// which case the goal is to lay the groundwork for turning a given
// relocation into an external reloc (to be applied by the external
// linker). For more on how relocations work in general, see
//
// "Linkers and Loaders", by John R. Levine (Morgan Kaufmann, 1999), ch. 7
//
// This is a performance-critical function for the linker; be careful
// to avoid introducing unnecessary allocations in the main loop.
func relocsym(ctxt *Link, s *sym.Symbol) { func relocsym(ctxt *Link, s *sym.Symbol) {
for ri := int32(0); ri < int32(len(s.R)); ri++ { for ri := int32(0); ri < int32(len(s.R)); ri++ {
r := &s.R[ri] r := &s.R[ri]

63
src/cmd/link/internal/ld/lib.go
View File

@ -91,28 +91,47 @@ import (
// THE SOFTWARE. // THE SOFTWARE.
type Arch struct { type Arch struct {
Funcalign int Funcalign int
Maxalign int Maxalign int
Minalign int Minalign int
Dwarfregsp int Dwarfregsp int
Dwarfreglr int Dwarfreglr int
Linuxdynld string Linuxdynld string
Freebsddynld string Freebsddynld string
Netbsddynld string Netbsddynld string
Openbsddynld string Openbsddynld string
Dragonflydynld string Dragonflydynld string
Solarisdynld string Solarisdynld string
Adddynrel func(*Link, *sym.Symbol, *sym.Reloc) bool Adddynrel func(*Link, *sym.Symbol, *sym.Reloc) bool
Archinit func(*Link) Archinit func(*Link)
Archreloc func(*Link, *sym.Reloc, *sym.Symbol, int64) (int64, bool) // Archreloc is an arch-specific hook that assists in
Archrelocvariant func(*Link, *sym.Reloc, *sym.Symbol, int64) int64 // relocation processing (invoked by 'relocsym'); it handles
Trampoline func(*Link, *sym.Reloc, *sym.Symbol) // target-specific relocation tasks. Here "rel" is the current
Asmb func(*Link) // relocation being examined, "sym" is the symbol containing the
Elfreloc1 func(*Link, *sym.Reloc, int64) bool // chunk of data to which the relocation applies, and "off" is the
Elfsetupplt func(*Link) // contents of the to-be-relocated data item (from sym.P). Return
Gentext func(*Link) // value is the appropriately relocated value (to be written back
Machoreloc1 func(*sys.Arch, *OutBuf, *sym.Symbol, *sym.Reloc, int64) bool // to the same spot in sym.P) and a boolean indicating
PEreloc1 func(*sys.Arch, *OutBuf, *sym.Symbol, *sym.Reloc, int64) bool // success/failure (a failing value indicates a fatal error).
Archreloc func(link *Link, rel *sym.Reloc, sym *sym.Symbol,
offset int64) (relocatedOffset int64, success bool)
// Archrelocvariant is a second arch-specific hook used for
// relocation processing; it handles relocations where r.Type is
// insufficient to describe the relocation (r.Variant !=
// sym.RV_NONE). Here "rel" is the relocation being applied, "sym"
// is the symbol containing the chunk of data to which the
// relocation applies, and "off" is the contents of the
// to-be-relocated data item (from sym.P). Return is an updated
// offset value.
Archrelocvariant func(link *Link, rel *sym.Reloc, sym *sym.Symbol,
offset int64) (relocatedOffset int64)
Trampoline func(*Link, *sym.Reloc, *sym.Symbol)
Asmb func(*Link)
Elfreloc1 func(*Link, *sym.Reloc, int64) bool
Elfsetupplt func(*Link)
Gentext func(*Link)
Machoreloc1 func(*sys.Arch, *OutBuf, *sym.Symbol, *sym.Reloc, int64) bool
PEreloc1 func(*sys.Arch, *OutBuf, *sym.Symbol, *sym.Reloc, int64) bool
// TLSIEtoLE converts a TLS Initial Executable relocation to // TLSIEtoLE converts a TLS Initial Executable relocation to
// a TLS Local Executable relocation. // a TLS Local Executable relocation.