Sped up allocateBranchIsland by skipping whole regions of allocated memory.

third_party/mach_override/chromium.patch

+diff --git a/third_party/mach_override/README.chromium b/third_party/mach_override/README.chromium
+index 8a7c3fd79e0b..9cd6b2452606 100644
+--- a/third_party/mach_override/README.chromium
++++ b/third_party/mach_override/README.chromium
+@@ -1,6 +1,5 @@
+ Name: mach_override
+ Short Name: mach_override
+-Version: Newer than 1.2. HEAD from branch semver-1.x.
+ URL: https://github.com/rentzsch/mach_override
+ Date: 2014-05-11
+ Revision: 919148f94db54fc04d287eb6a42c0c36b166bbfa
+@@ -16,4 +15,5 @@ mach_override includes a copy of libudis86 1.7.1, available separately from
+ http://udis86.sourceforge.net/ and https://github.com/vmt/udis86 .
+ 
+ 
+-Local Modifications: None.
++Local Modifications: Sped up allocation of branch island memory via usage of
++   vm_region to skip already allocated pages.
+diff --git a/third_party/mach_override/chromium.patch b/third_party/mach_override/chromium.patch
+new file mode 100644
+index 000000000000..e69de29bb2d1
+diff --git a/third_party/mach_override/mach_override.c b/third_party/mach_override/mach_override.c
+index 85a75e5c2067..2747f294cfa8 100644
+--- a/third_party/mach_override/mach_override.c
++++ b/third_party/mach_override/mach_override.c
+@@ -41,7 +41,7 @@ long kIslandTemplate[] = {
+ #define kInstructionHi         10
+ #define kInstructionLo         11
+ 
+-#elif defined(__i386__) 
++#elif defined(__i386__)
+ 
+ #define kOriginalInstructionsSize 16
+ 
+@@ -61,6 +61,7 @@ char kIslandTemplate[] = {
+ #define kOriginalInstructionsSize 32
+ 
+ #define kJumpAddress    kOriginalInstructionsSize + 6
++#define kMaxJumpOffset  (0x7fffffffUL)
+ 
+ char kIslandTemplate[] = {
+        // kOriginalInstructionsSize nop instructions so that we 
+@@ -267,7 +268,13 @@ mach_override_ptr(
+ 
+ #if defined(__i386__) || defined(__x86_64__)
+        if (!err) {
+-               uint32_t addressOffset = ((char*)escapeIsland - (char*)originalFunctionPtr - 5);
++               // TODO: On 64-bit, move to opcode FF/4 (jmp 64-bit absolute indirect)
++               // instead of E9 (jmp 32-bit relative to RIP). Then we should update
++               // allocateBranchIsland to simply allocate any page in the address space.
++               // See the 64-bit version of kIslandTemplate array.
++               int64_t addressOffset64 = ((char*)escapeIsland - (char*)originalFunctionPtr - 5);
++               int32_t addressOffset = ((char*)escapeIsland - (char*)originalFunctionPtr - 5);
++               assert(addressOffset64 == addressOffset);
+                addressOffset = OSSwapInt32(addressOffset);
+                
+                jumpRelativeInstruction |= 0xE900000000000000LL; 
+@@ -385,7 +392,7 @@ allocateBranchIsland(
+                void *originalFunctionAddress)
+ {
+        assert( island );
+-       
++
+        mach_error_t    err = err_none;
+        
+        if( allocateHigh ) {
+@@ -401,23 +408,41 @@ allocateBranchIsland(
+                vm_address_t first = 0xfeffffff;
+                vm_address_t last = 0xfe000000 + PAGE_SIZE;
+ #elif defined(__x86_64__)
+-               // 64-bit ASLR is in bits 13-28
+-               vm_address_t first = ((uint64_t)originalFunctionAddress & ~( (0xFUL << 28) | (PAGE_SIZE - 1) ) ) | (0x1UL << 31);
+-               vm_address_t last = (uint64_t)originalFunctionAddress & ~((0x1UL << 32) - 1);
++               // This logic is more complex due to the 32-bit limit of the jump out
++               // of the original function. Once that limitation is removed, we can
++               // use vm_allocate with VM_FLAGS_ANYWHERE as in the i386 code above.
++               const uint64_t kPageMask = ~(PAGE_SIZE - 1);
++               vm_address_t first = (uint64_t)originalFunctionAddress - kMaxJumpOffset;
++               first = (first & kPageMask) + PAGE_SIZE; // Align up to the next page start
++               if (first > (uint64_t)originalFunctionAddress) first = 0;
++               vm_address_t last = (uint64_t)originalFunctionAddress + kMaxJumpOffset;
++               if (last < (uint64_t)originalFunctionAddress) last = ULONG_MAX;
+ #endif
+ 
+                page = first;
+                int allocated = 0;
+                vm_map_t task_self = mach_task_self();
+ 
+-               while( !err && !allocated && page != last ) {
++               while( !err && !allocated && page < last ) {
+ 
+                        err = vm_allocate( task_self, &page, PAGE_SIZE, 0 );
+                        if( err == err_none )
+                                allocated = 1;
+                        else if( err == KERN_NO_SPACE ) {
+ #if defined(__x86_64__)
+-                               page -= PAGE_SIZE;
++                               // This memory region is not suitable, skip it:
++                               vm_size_t region_size;
++                               mach_msg_type_number_t int_count = VM_REGION_BASIC_INFO_COUNT_64;
++                               vm_region_basic_info_data_64_t vm_region_info;
++                               mach_port_t object_name;
++                               // The call will move 'page' to the beginning of the region:
++                               err = vm_region_64(task_self, &page, &region_size,
++                                                       VM_REGION_BASIC_INFO_64, (vm_region_info_t)&vm_region_info,
++                                                       &int_count, &object_name);
++                               if (err == KERN_SUCCESS)
++                                       page += region_size;
++                               else
++                                       break;
+ #else
+                                page += PAGE_SIZE;
+ #endif
+@@ -438,7 +463,7 @@ allocateBranchIsland(
+        }
+        if( !err )
+                (**island).allocatedHigh = allocateHigh;
+-       
++
+        return err;
+ }
+