Many -no-pie/-shared/-pie applications linked against glibc or musl
should work with this patch. This also helps FreeBSD rtld (PR40888).
* Fix default image base and max page size.
* Support new-style Secure PLT (see below). Old-style BSS PLT is not
implemented, so it is not suitable for FreeBSD rtld now because it doesn't
support Secure PLT yet.
* Support more relocation types: R_PPC_REL16*, R_PPC_LOCAL24PC, R_PPC_PLTREL24, and R_PPC_GOT16
R_PPC_ADDR32, R_PPC_REL16*, R_PPC_LOCAL24PC, R_PPC_PLTREL24, and R_PPC_GOT16.
The addend of R_PPC_PLTREL24 is special: it decides the call stub PLT types
but it should be ignored for the computation of target symbol VA.
* Support .glink used for lazy PLT resolution in glibc
* Add a new thunk type: PPC32PltCallStub that is similar to PPC64PltCallStub. It is
It is used by R_PPC_REL24 and R_PPC_PLTREL24.
A PLT stub used in -fPIE/-fPIC usually loads an address relative to
.got2+0x8000 (-fpie/-fpic code uses _GLOBAL_OFFSET_TABLE_ relative
addresses).
2Two .got2 sections in two object files have different addresses, thus a PLT stub
can't be shared by two object files. To handle this incompatibility,
change the parameters of Thunk::isCompatibleWith to `const InputSection
`const InputSection &` + `const Relocation &`.
PowerPC psABI specified an old-style .plt (BSS PLT) (.plt is NOBITS and
written by the dynamic loader) that is both writable and executable.
Linkers don't make separate RW-writable and RWE segments,executable. which causes allLinkers don't make separate RW- and RWE segments,
which causes all initially writable memory (think .data) executable. This is a big
This is a big security concern so a new PLT scheme (secure PLT) was developed to
address the security issue.
TLS is not implemented but I believe PPC.cpp can just reuse some TLS code
from PPC64.cpp. For tests, I create ppc32-* instead of ppc-* because I plan to
use ppc-* for tests shareable on ppc32 and ppc64will be implemented in D62940.
glibc older than ~2012 can not handle the DT_RELA+DT_RELASZ == DT_JMPREL
case correctly. A hack (not included in this patch) in LinkerScript.cpp
addOrphanSections() is required:
if (Config->EMachine == EM_PPC) {
// Older glibc assumes .rela.dyn includes .rela.plt
Add(In.RelaDyn);
if (In.RelaPlt->isLive() && !In.RelaPlt->Parent)
In.RelaDyn->getParent()->addSection(In.RelaPlt);
}