From 12ba711f35b43c1f9234bd644ee438fdb5fb05a4 Mon Sep 17 00:00:00 2001 From: Krzysztof Parzyszek Date: Wed, 20 Feb 2013 19:25:09 +0000 Subject: Add comment in Memory.inc explaining r175646. llvm-svn: 175650 --- llvm/lib/Support/Unix/Memory.inc | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'llvm/lib/Support/Unix/Memory.inc') diff --git a/llvm/lib/Support/Unix/Memory.inc b/llvm/lib/Support/Unix/Memory.inc index a66e3c7aeee..e00394ec6aa 100644 --- a/llvm/lib/Support/Unix/Memory.inc +++ b/llvm/lib/Support/Unix/Memory.inc @@ -52,6 +52,13 @@ int getPosixProtectionFlags(unsigned Flags) { return PROT_READ | PROT_WRITE | PROT_EXEC; case llvm::sys::Memory::MF_EXEC: #if defined(__FreeBSD__) + // On PowerPC, having an executable page that has no read permission + // can have unintended consequences. The function InvalidateInstruction- + // Cache uses instructions dcbf and icbi, both of which are treated by + // the processor as loads. If the page has no read permissions, + // executing these instructions will result in a segmentation fault. + // Somehow, this problem is not present on Linux, but it does happen + // on FreeBSD. return PROT_READ | PROT_EXEC; #else return PROT_EXEC; -- cgit v1.2.3