Currently, the symbol updater uses a pointer pointing to the
loader's payloads array. If the payloads slice grows (and moves),
the pointer may become stale and no longer point to the symbol's
actual payload. Specifically, consider
sb, sym := l.MakeSymbolUpdater(...)
// add a bunch of external symbols, which grows payload slice
sb.SetType(t)
l.SymType(sym) // may not return t
sb.SetType on line 3 may not have the desired effect, as
sb.extSymPayload may no longer point to the right payload. As a
result, the type we get on line 4 may be not the one we set.
Fix this by making the payload's address permanent. Once it is
allocated it will never move.
Change-Id: Iab190ea5aceb5c37f91d09ad4ffd458e881b03f4
Reviewed-on: https://go-review.googlesource.com/c/go/+/217063
Run-TryBot: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Revamp the way that symbol overwrites are handled to deal with symbols
that are overwritten more than once (such as "_cgo_mmap"). The
scenario here is that a symbol can be overwritten twice, once during
preload, and then again when host objects are read during internal
linking. This can result in a situation where we have two entries in
the overwrite map, from X -> Y and then from Y -> Z. Rather than
search the overwrite map when adding new entries, add a helper routine
for querying the map that catches this situation and fixes it up.
Also with this patch is a couple of tweaks to the loader.Dump method
to insure that it can dump the entire global index space without
crashing due to odd overwrites (as in the scenario above).
Change-Id: Ib6c8a0e03e92fc2b57318001711b501eeaf12249
Reviewed-on: https://go-review.googlesource.com/c/go/+/212098
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Add in the hooks to SymbolBuilder and to the loader to allow
the linker to make modifications to a non-external symbol (e.g.
a sym whose index is less than loader.extStart).
The basic idea is to manufacture a new external symbol with the same
name and version, then import the old symbol's content (type, data,
relocations, etc) into the payload struct for the new symbol, and
finally redirect the name lookup tables to target the new sym for the
specified name/version.
This change is needed in order to convert over the host object loaders
to avoid use of sym.Symbol.
Change-Id: I79cd42b23794e830bbdbcbcd2c500c35c351f01f
Reviewed-on: https://go-review.googlesource.com/c/go/+/211897
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Add SymbolBuilder helper type -- this type provides a set of methods
intended to make it easy to manipulate the content of a symbol (type,
relocations, data, etc).
Change-Id: I579bf8d04650e66d33a9780a6c2347a576c94c6f
Reviewed-on: https://go-review.googlesource.com/c/go/+/210178
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Jeremy Faller <jeremy@golang.org>
