Commit Graph

4 Commits

Author SHA1 Message Date
Simon Dardis cd8758233e [mips][lld] Spectre variant two mitigation for MIPSR2
This patch provides migitation for CVE-2017-5715, Spectre variant two,
which affects the P5600 and P6600. It implements the LLD part of
-z hazardplt. Like the Clang part of this patch, I have opted for that
specific option name in case alternative migitation methods are required
in the future.

The mitigation strategy suggested by MIPS for these processors is to use
hazard barrier instructions. 'jalr.hb' and 'jr.hb' are hazard
barrier variants of the 'jalr' and 'jr' instructions respectively.

These instructions impede the execution of instruction stream until
architecturally defined hazards (changes to the instruction stream,
privileged registers which may affect execution) are cleared. These
instructions in MIPS' designs are not speculated past.

These instructions are defined by the MIPS32R2 ISA, so this mitigation
method is not compatible with processors which implement an earlier
revision of the MIPS ISA.

For LLD, this changes PLT stubs to use 'jalr.hb' and 'jr.hb'.

Reviewers: atanasyan, ruiu

Differential Revision: https://reviews.llvm.org/D43488

llvm-svn: 325647
2018-02-20 23:49:17 +00:00
Petar Jovanovic 661102a339 [mips] update expected output in test/ELF/mips-plt-r6.s
r306095 in LLVM has changed register positions for instruction aui.
This change updates the test that checks for aui.

llvm-svn: 306173
2017-06-23 22:30:28 +00:00
Peter Collingbourne 628ec9f193 ELF: Place relro sections after non-relro sections in r/w segment.
This is in preparation for my next change, which will introduce a relro
nobits section. That requires that relro sections appear at the end of the
progbits part of the r/w segment so that the relro nobits section can appear
contiguously.

Because of the amount of churn required in the test suite, I'm making this
change separately.

llvm-svn: 291523
2017-01-10 01:21:30 +00:00
Simon Atanasyan a088bce959 [ELF][MIPS] Create PLT entry specific for MIPS ABI version R6
llvm-svn: 276173
2016-07-20 20:15:33 +00:00