Some NFC changes to how we scan of kexts & kernels in memory in the
DynamicLoaderDarwinKernel plugin. Created a new function ReadMachHeader
and instead of reading through the target cached memory reader,
start by reading only a mach header sized chunk of memory, then
check it for a valid mach-o magic # and use the size of the load
commands to pre-fetch the entire load commands of the kext which
is the only thing we're going to read, instead of letting the generic
mach-o parser read it in 512 byte chunks.
Functionally this is doing exactly the same thing as before, but by
cutting down on the # of packets going back and forth, even on a
local connection it's close to a quarter faster than it was before.
<rdar://problem/38570146>
git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@334995 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp b/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
index fbf255a..6d114d9 100644
--- a/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
+++ b/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
@@ -8,8 +8,6 @@
//
//===----------------------------------------------------------------------===//
-#include "lldb/Utility/SafeMachO.h"
-
#include "Plugins/Platform/MacOSX/PlatformDarwinKernel.h"
#include "lldb/Breakpoint/StoppointCallbackContext.h"
#include "lldb/Core/Debugger.h"
@@ -368,9 +366,50 @@
}
//----------------------------------------------------------------------
+// Read the mach_header struct out of memory and return it.
+// Returns true if the mach_header was successfully read,
+// Returns false if there was a problem reading the header, or it was not
+// a Mach-O header.
+//----------------------------------------------------------------------
+
+bool
+DynamicLoaderDarwinKernel::ReadMachHeader(addr_t addr, Process *process, llvm::MachO::mach_header &header) {
+ Status read_error;
+
+ // Read the mach header and see whether it looks like a kernel
+ if (process->DoReadMemory (addr, &header, sizeof(header), read_error) !=
+ sizeof(header))
+ return false;
+
+ const uint32_t magicks[] = { llvm::MachO::MH_MAGIC_64, llvm::MachO::MH_MAGIC, llvm::MachO::MH_CIGAM, llvm::MachO::MH_CIGAM_64};
+
+ bool found_matching_pattern = false;
+ for (size_t i = 0; i < llvm::array_lengthof (magicks); i++)
+ if (::memcmp (&header.magic, &magicks[i], sizeof (uint32_t)) == 0)
+ found_matching_pattern = true;
+
+ if (found_matching_pattern == false)
+ return false;
+
+ if (header.magic == llvm::MachO::MH_CIGAM ||
+ header.magic == llvm::MachO::MH_CIGAM_64) {
+ header.magic = llvm::ByteSwap_32(header.magic);
+ header.cputype = llvm::ByteSwap_32(header.cputype);
+ header.cpusubtype = llvm::ByteSwap_32(header.cpusubtype);
+ header.filetype = llvm::ByteSwap_32(header.filetype);
+ header.ncmds = llvm::ByteSwap_32(header.ncmds);
+ header.sizeofcmds = llvm::ByteSwap_32(header.sizeofcmds);
+ header.flags = llvm::ByteSwap_32(header.flags);
+ }
+
+ return true;
+}
+
+//----------------------------------------------------------------------
// Given an address in memory, look to see if there is a kernel image at that
-// address. Returns a UUID; if a kernel was not found at that address,
-// UUID.IsValid() will be false.
+// address.
+// Returns a UUID; if a kernel was not found at that address, UUID.IsValid()
+// will be false.
//----------------------------------------------------------------------
lldb_private::UUID
DynamicLoaderDarwinKernel::CheckForKernelImageAtAddress(lldb::addr_t addr,
@@ -384,42 +423,14 @@
"looking for kernel binary at 0x%" PRIx64,
addr);
- // First try a quick test -- read the first 4 bytes and see if there is a
- // valid Mach-O magic field there (the first field of the
- // mach_header/mach_header_64 struct).
-
- Status read_error;
- uint8_t magicbuf[4];
- if (process->ReadMemoryFromInferior (addr, magicbuf, sizeof (magicbuf), read_error) != sizeof (magicbuf))
- return UUID();
-
- const uint32_t magicks[] = { llvm::MachO::MH_MAGIC_64, llvm::MachO::MH_MAGIC, llvm::MachO::MH_CIGAM, llvm::MachO::MH_CIGAM_64};
-
- bool found_matching_pattern = false;
- for (size_t i = 0; i < llvm::array_lengthof (magicks); i++)
- if (::memcmp (magicbuf, &magicks[i], sizeof (magicbuf)) == 0)
- found_matching_pattern = true;
-
- if (found_matching_pattern == false)
- return UUID();
-
- // Read the mach header and see whether it looks like a kernel
llvm::MachO::mach_header header;
- if (process->DoReadMemory(addr, &header, sizeof(header), read_error) !=
- sizeof(header))
+
+ if (ReadMachHeader (addr, process, header) == false)
return UUID();
- if (header.magic == llvm::MachO::MH_CIGAM ||
- header.magic == llvm::MachO::MH_CIGAM_64) {
- header.magic = llvm::ByteSwap_32(header.magic);
- header.cputype = llvm::ByteSwap_32(header.cputype);
- header.cpusubtype = llvm::ByteSwap_32(header.cpusubtype);
- header.filetype = llvm::ByteSwap_32(header.filetype);
- header.ncmds = llvm::ByteSwap_32(header.ncmds);
- header.sizeofcmds = llvm::ByteSwap_32(header.sizeofcmds);
- header.flags = llvm::ByteSwap_32(header.flags);
- }
-
+ // First try a quick test -- read the first 4 bytes and see if there is a
+ // valid Mach-O magic field there
+ // (the first field of the mach_header/mach_header_64 struct).
// A kernel is an executable which does not have the dynamic link object flag
// set.
if (header.filetype == llvm::MachO::MH_EXECUTE &&
@@ -639,8 +650,17 @@
FileSpec file_spec;
file_spec.SetFile(m_name.c_str(), false, FileSpec::Style::native);
+ llvm::MachO::mach_header mh;
+ size_t size_to_read = 512;
+ if (ReadMachHeader (m_load_address, process, mh)) {
+ if (mh.magic == llvm::MachO::MH_CIGAM || llvm::MachO::MH_MAGIC)
+ size_to_read = sizeof (llvm::MachO::mach_header) + mh.sizeofcmds;
+ if (mh.magic == llvm::MachO::MH_CIGAM_64 || llvm::MachO::MH_MAGIC_64)
+ size_to_read = sizeof (llvm::MachO::mach_header_64) + mh.sizeofcmds;
+ }
+
ModuleSP memory_module_sp =
- process->ReadModuleFromMemory(file_spec, m_load_address);
+ process->ReadModuleFromMemory(file_spec, m_load_address, size_to_read);
if (memory_module_sp.get() == NULL)
return false;
diff --git a/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.h b/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.h
index ad4f7c6..75998f1 100644
--- a/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.h
+++ b/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.h
@@ -17,6 +17,9 @@
#include <vector>
// Other libraries and framework includes
+
+#include "lldb/Utility/SafeMachO.h"
+
// Project includes
#include "lldb/Target/DynamicLoader.h"
#include "lldb/Target/Process.h"
@@ -284,6 +287,9 @@
static lldb::addr_t
SearchForKernelViaExhaustiveSearch(lldb_private::Process *process);
+ static bool
+ ReadMachHeader(lldb::addr_t addr, lldb_private::Process *process, llvm::MachO::mach_header &mh);
+
static lldb_private::UUID
CheckForKernelImageAtAddress(lldb::addr_t addr,
lldb_private::Process *process);
