tag 38cde876c5c92198fde69a8cb3bb3c3d13df35c9
tagger Borislav Petkov <bp@suse.de> Sun Jun 28 16:07:12 2020 +0200
object 0f1441b44e823a74f3f3780902a113e07c73fbf6

Peter Zijlstra says:

Address KCOV vs noinstr. There is no function attribute to selectively
suppress KCOV instrumentation, instead teach objtool to NOP out the
calls in noinstr functions.

This cures a bunch of KCOV crashes (as used by syzcaller).

commit 0f1441b44e823a74f3f3780902a113e07c73fbf6
author Peter Zijlstra <peterz@infradead.org> Fri Jun 12 16:05:26 2020 +0200
committer Peter Zijlstra <peterz@infradead.org> Thu Jun 18 17:36:33 2020 +0200
tree 5ef3755754810974096c758d5878dc31d23d7c20
parent fdabdd0b05e0bdf232340d5da86563ed142a99a7

objtool: Fix noinstr vs KCOV

Since many compilers cannot disable KCOV with a function attribute,
help it to NOP out any __sanitizer_cov_*() calls injected in noinstr
code.

This turns:

12:   e8 00 00 00 00          callq  17 <lockdep_hardirqs_on+0x17>
		13: R_X86_64_PLT32      __sanitizer_cov_trace_pc-0x4

into:

12:   0f 1f 44 00 00          nopl   0x0(%rax,%rax,1)
		13: R_X86_64_NONE      __sanitizer_cov_trace_pc-0x4

Just like recordmcount does.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>