tree 28c2e417c2c35657511fa720b5c30bce36b17d11
parent 81080a729af568f7b5fde92b9170cc17065027c9
author Peter Collingbourne <pcc@google.com> 1565220650 -0700
committer CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org> 1565287423 +0000

Add assembly support for -fsanitize=hwaddress tagged globals.

As of LLVM r368102, Clang will set a pointer tag in bits 56-63 of the
address of a global when compiling with -fsanitize=hwaddress. This requires
an adjustment to assembly code that takes the address of such globals: the
code cannot use the regular R_AARCH64_ADR_PREL_PG_HI21 relocation to refer
to the global, since the tag would take the address out of range. Instead,
the code must use the non-checking (_NC) variant of the relocation (the
link-time check is substituted by a runtime check).

This change makes the necessary adjustment in all of the places where it
is needed when compiling with -fsanitize=hwaddress. While here, shrink the
code by an instruction in each of those places by folding the addend into
the load, and remove some dead code that seems to have been left over from
commit 293d9ee4e837d122a28cd992e37779a5de48dc7f.

We check for a sufficiently new clang before using the :pg_hi21_nc: relocation
variant because support for this variant was only added recently.

Change-Id: Ic9da8386e19c03c1e90c103a81232a254277e9a5
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/36924
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>