[Lldb-commits] [lldb] r258387 - When ObjectFileMachO reads a Mach-O file for a 32-bit arm cpu,

[Jason Molenda via lldb-commits]

Author: jmolenda
Date: Wed Jan 20 22:38:05 2016
New Revision: 258387

URL: http://llvm.org/viewvc/llvm-project?rev=258387&view=rev
Log:
When ObjectFileMachO reads a Mach-O file for a 32-bit arm cpu,
set the triple's "vendor" field to Apple.  

We don't want to assume a vendor of Apple for all Mach-O files -
this breaks x86_64 EFI debugging where they put non-Apple binaries
in a Mach-O format for ease of handling.

But on armv7, Apple's ABI always uses r7 as the frame pointer
register; if we don't set the Vendor field to Apple, we can pick
up a generic armv7 ABI where the fp is r11 (or r7 for thumb) which
breaks backtracing altogether.

Greg is reluctant for us to make any assumptions about the Vendor
here, but we'll see how this shakes out.  It's such a big problem
on armv7 if we don't know this is using the Apple ABI that it's worth
trying this approach.

<rdar://problem/22137561> 

Modified:
    lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp

Modified: lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp?rev=258387&r1=258386&r2=258387&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp (original)
+++ lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp Wed Jan 20 22:38:05 2016
@@ -4828,9 +4828,22 @@ ObjectFileMachO::GetArchitecture (const
 
         if (header.filetype == MH_PRELOAD)
         {
-            // Set vendor to an unspecified unknown or a "*" so it can match any vendor
-            triple.setVendor(llvm::Triple::UnknownVendor);
-            triple.setVendorName(llvm::StringRef());
+            if (header.cputype == CPU_TYPE_ARM)
+            {
+                // If this is a 32-bit arm binary, and it's a standalone binary,
+                // force the Vendor to Apple so we don't accidentally pick up 
+                // the generic armv7 ABI at runtime.  Apple's armv7 ABI always uses
+                // r7 for the frame pointer register; most other armv7 ABIs use a
+                // combination of r7 and r11.
+                triple.setVendor(llvm::Triple::Apple);
+            }
+            else
+            {
+                // Set vendor to an unspecified unknown or a "*" so it can match any vendor
+                // This is required for correct behavior of EFI debugging on x86_64
+                triple.setVendor(llvm::Triple::UnknownVendor);
+                triple.setVendorName(llvm::StringRef());
+            }
             return true;
         }
         else