The directives I added in r323466 and r323501 did not define a valid
CFA until several instructions into the associated functions. This
triggers an assertion in GDB when generating a stack trace while
stopped at the first instruction of PLT stub entry point since there
is no valid CFA rule for the first instruction.
This is probably just wrong on my part as the non-simple .cfi_startproc
would have defined a valid CFA. Instead, define a valid CFA as sp + 0
at the start of the functions and then use .cfa_def_offset to change the
offset when sp is adjusted later in the function.
Sponsored by: DARPA / AFRL
This is only cosmetic, but the entry point for rtld is not a leaf function,
and this avoids two .frame directives for rtld_start.
Sponsored by: DARPA / AFRL
Newer binutils supports extensions to the MIPS ABI for non-PIC code
that is used when compiling O32 binaries with clang 5 (but not used
for N64 oddly enough). These extensions require support for
R_MIPS_COPY relocations as well as a second PLT GOT using
R_MIPS_JUMP_SLOT relocations.
For R_MIPS_COPY, use the same approach as on other architectures where
fixups are deferred to the MD do_copy_relocations.
The additional PLT GOT for jump slots is located in a .got.plt section
which is identified by a DT_MIPS_PLTGOT dynamic entry. This GOT also
requires fixups for the first two GOT entries just as the normal GOT.
However, the entry point for this second GOT uses a different calling
convention. Rather than passing an offset into the GOT, it passes an
offset into the .rel.plt section. This requires a second entry point
(_rtld_pltbind_start) which calls the normal _rtld_bind() rather than
_mips_rtld_bind(). This also means providing a real version of
reloc_jmpslot() which is used by _rtld_bind().
In addition, add real implementions of reloc_plt() and
reloc_jmpslots() which walk .rel.plt handling R_MIPS_JUMP_SLOT
relocations.
Reviewed by: kib
Sponsored by: DARPA / AFRL
Differential Revision: https://reviews.freebsd.org/D12326
This code came from the merged mips2 and Juniper mips repositories.
Warner Losh, Randall Seager, Oleksandr Tymoshenko and Olivier Houchard
worked to merge, debug and integrate this code. This code may also
contain code derived from NetBSD.
