tree 7bae861b2ea0920d87671be4520076f46357e0b8
parent b056ed304d37b4f3103f7f77939b92629fbda729
author David Benjamin <davidben@google.com> 1494882951 -0400
committer CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org> 1494891195 +0000

Fix GOTPCREL accesses to symbols defined outside the module.

5c38c05b2657739daea2ca01a93900e30ee3764f caused foo@GOTPCREL for
external foo to resolve to bcm_redirector_foo. This is morally
equivalent to using foo@PLT when a pointer to foo is needed. But this
does not work if foo is data. Notably, this ended up mangling
OPENSSL_ia32cap_P because it failed to recognize it as an symbol in the
library (but external to the module). It also mangles some things that
ASan emits.

(It also breaks non-NULL function pointer comparisons, but those are
silly.)

Instead, apply a variation of the OPENSSL_ia32cap_addr_delta trick that
works for the GOT. "addr_delta" is really weird, so I'm calling this an
"external relocation". This causes fprintf(stderr) to work and also
seems to keep ASan compiling. I was unable to reproduce the case that
5c38c05b2657739daea2ca01a93900e30ee3764f added the bcm_redirector_foo
transform for.

Also tighten up the pattern. No need to reference a bit of memory twice
since we just loaded it into a register.

Change-Id: If5520fc0887e83e23a08828e40fbbed9e47d912e
Reviewed-on: https://boringssl-review.googlesource.com/16345
Commit-Queue: David Benjamin <davidben@google.com>
Commit-Queue: Adam Langley <agl@google.com>
Reviewed-by: Adam Langley <agl@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>