From be46d3871c91902504e5ec4c7f575c86f647aafc Mon Sep 17 00:00:00 2001
From: Evgenii Stepanov <eugenis@google.com>
Date: Fri, 27 Jan 2017 13:42:03 -0800
Subject: Fix CFI initialization crash on x86.

Bug: 34752378
Test: bionic tests
Change-Id: If8e33f76a1a2d83356d818fed506ea624f579860
---
 libdl/libdl_cfi.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'libdl')

diff --git a/libdl/libdl_cfi.cpp b/libdl/libdl_cfi.cpp
index 362b093fa..8458564a8 100644
--- a/libdl/libdl_cfi.cpp
+++ b/libdl/libdl_cfi.cpp
@@ -29,10 +29,12 @@ static struct {
   char padding[PAGE_SIZE - sizeof(v)];
 } shadow_base_storage alignas(PAGE_SIZE);
 
+// __cfi_init is called by the loader as soon as the shadow is mapped. This may happen very early
+// during startup, before libdl.so global constructors, and, on i386, even before __libc_sysinfo is
+// initialized. This function should not do any system calls.
 extern "C" uintptr_t* __cfi_init(uintptr_t shadow_base) {
   shadow_base_storage.v = shadow_base;
   static_assert(sizeof(shadow_base_storage) == PAGE_SIZE, "");
-  mprotect(&shadow_base_storage, PAGE_SIZE, PROT_READ);
   return &shadow_base_storage.v;
 }
 
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