This patch makes the following symbols (relatively) consistent between

all of our linker scripts:

_text
_etext
_text_size
_data
_edata
_data_size

There are various things that are slightly different (positions of
.rela*, .dynamic, and similar in relation to .data), but _text and _data
are now always at the beginning of their respective sections with regard
to how a debuger would reference the debug info, and _etext and _edata
are now always extant and guaranteed to be after any of the respective
kind of data the debugger would look for in that section.

This also adds an application example of how it might be used, and a
makefile target for %.efi.debug which will generate a separate debuginfo
file for that example.

This also enables debugging by default (i.e. -g is in CFLAGS) and adds
.note.gnu.build-id sections to our .so files (i.e. --build-id=sha1 is in
LDFLAGS).

Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Nigel Croxon <nigel.croxon@hp.com>

.gitignore

@@ -1,4 +1,5 @@
 *.efi
+*.efi.debug
 *.o
 *.a
 *.tar.*

Make.defaults

@@ -140,13 +140,14 @@ INCDIR  += -I$(SRCDIR) -I$(TOPDIR)/inc -I$(TOPDIR)/inc/$(ARCH) \
            -I$(TOPDIR)/inc/protocol
 
 ifeq (FreeBSD, $(findstring FreeBSD, $(OS)))
-CFLAGS  += $(ARCH3264) -O2 -fpic -Wall -fshort-wchar -fno-strict-aliasing \
+CFLAGS  += $(ARCH3264) -g -O2 -fpic -Wall -fshort-wchar -fno-strict-aliasing \
            -ffreestanding -fno-stack-protector
 else
-CFLAGS  += $(ARCH3264) -O2 -fpic -Wall -fshort-wchar -fno-strict-aliasing \
+CFLAGS  += $(ARCH3264) -g -O2 -fpic -Wall -fshort-wchar -fno-strict-aliasing \
            -fno-merge-constants -ffreestanding -fno-stack-protector       \
            -fno-stack-check
 endif
 
 ASFLAGS += $(ARCH3264)
-LDFLAGS	+= -nostdlib --warn-common --no-undefined --fatal-warnings
+LDFLAGS	+= -nostdlib --warn-common --no-undefined --fatal-warnings \
+	   --build-id=sha1

Make.rules

@@ -39,6 +39,12 @@
 		    -j .rela -j .rel.* -j .rela.* -j .rel* -j .rela* \
 		    -j .reloc $(FORMAT) $*.so $@
 
+%.efi.debug: %.so
+	$(OBJCOPY) -j .debug_info -j .debug_abbrev -j .debug_aranges \
+		-j .debug_line -j .debug_str -j .debug_ranges \
+		-j .note.gnu.build-id \
+		$(FORMAT) $*.so $@
+
 %.so: %.o
 	$(LD) $(LDFLAGS) $^ -o $@ $(LOADLIBES)
 

apps/Makefile

@@ -61,7 +61,7 @@ LOADLIBES	+= -T $(LDSCRIPT)
 TARGET_APPS = t.efi t2.efi t3.efi t4.efi t5.efi t6.efi \
 	      printenv.efi t7.efi t8.efi tcc.efi modelist.efi \
 	      route80h.efi drv0_use.efi AllocPages.efi \
-	      FreePages.efi setjmp.efi
+	      FreePages.efi setjmp.efi debughook.efi debughook.efi.debug
 TARGET_BSDRIVERS = drv0.efi
 TARGET_RTDRIVERS =
 

apps/debughook.c

@@ -0,0 +1,92 @@
+#include <efi.h>
+#include <efilib.h>
+
+EFI_STATUS
+GetVariableAttr(CHAR16 *var, UINT8 **data, UINTN *len, EFI_GUID owner,
+		  UINT32 *attributes)
+{
+	EFI_STATUS efi_status;
+
+	*len = 0;
+
+	efi_status = uefi_call_wrapper(RT->GetVariable, 5, var, &owner,
+				       NULL, len, NULL);
+	if (efi_status != EFI_BUFFER_TOO_SMALL)
+		return efi_status;
+
+	*data = AllocateZeroPool(*len);
+	if (!*data)
+		return EFI_OUT_OF_RESOURCES;
+
+	efi_status = uefi_call_wrapper(RT->GetVariable, 5, var, &owner,
+				       attributes, len, *data);
+
+	if (efi_status != EFI_SUCCESS) {
+		FreePool(*data);
+		*data = NULL;
+	}
+	return efi_status;
+}
+
+EFI_STATUS
+GetVariable(CHAR16 *var, UINT8 **data, UINTN *len, EFI_GUID owner)
+{
+	return GetVariableAttr(var, data, len, owner, NULL);
+}
+
+EFI_GUID DUMMY_GUID =
+{0x55aad538, 0x8f82, 0x4e2a, {0xa4,0xf0,0xbe, 0x59, 0x13, 0xb6, 0x5f, 0x1e}};
+
+static void
+__attribute__((__optimize__("0")))
+DebugHook(void)
+{
+	EFI_GUID guid = DUMMY_GUID;
+	UINT8 *data = NULL;
+	UINTN dataSize = 0;
+	EFI_STATUS efi_status;
+	volatile register UINTN x = 0;
+	extern char _text, _data;
+
+	if (x)
+		return;
+
+	efi_status = GetVariable(L"DUMMY_DEBUG", &data, &dataSize, guid);
+	if (EFI_ERROR(efi_status)) {
+		return;
+	}
+
+	Print(L"add-symbol-file /usr/lib/debug/boot/efi/debughook.debug "
+	      L"0x%08x -s .data 0x%08x\n", &_text, &_data);
+
+	Print(L"Pausing for debugger attachment.\n");
+	Print(L"To disable this, remove the EFI variable DUMMY_DEBUG-%g .\n",
+	      &guid);
+	x = 1;
+	while (x++) {
+		/* Make this so it can't /totally/ DoS us. */
+#if defined(__x86_64__) || defined(__i386__) || defined(__i686__)
+		if (x > 4294967294)
+			break;
+		__asm__ __volatile__("pause");
+#elif defined(__aarch64__)
+		if (x > 1000)
+			break;
+		__asm__ __volatile__("wfi");
+#else
+		if (x > 12000)
+			break;
+		uefi_call_wrapper(BS->Stall, 1, 5000);
+#endif
+	}
+	x = 1;
+}
+
+
+EFI_STATUS
+efi_main (EFI_HANDLE image, EFI_SYSTEM_TABLE *systab)
+{
+	InitializeLib(image, systab);
+	DebugHook();
+	return EFI_SUCCESS;
+}

gnuefi/elf_aarch64_efi.lds

@@ -4,6 +4,7 @@ ENTRY(_start)
 SECTIONS
 {
   .text 0x0 : {
+    _text = .;
     *(.text.head)
     *(.text)
     *(.text.*)
@@ -11,11 +12,13 @@ SECTIONS
     *(.srodata)
     *(.rodata*)
     . = ALIGN(16);
-    _etext = .;
   }
+  _etext = .;
+  _text_size = . - _text;
   .dynamic  : { *(.dynamic) }
   .data :
   {
+   _data = .;
    *(.sdata)
    *(.data)
    *(.data1)

gnuefi/elf_arm_efi.lds

@@ -4,6 +4,7 @@ ENTRY(_start)
 SECTIONS
 {
   .text 0x0 : {
+    _text = .;
     *(.text.head)
     *(.text)
     *(.text.*)
@@ -11,11 +12,13 @@ SECTIONS
     *(.srodata)
     *(.rodata*)
     . = ALIGN(16);
-    _etext = .;
   }
+  _etext = .;
+  _text_size = . - _text;
   .dynamic  : { *(.dynamic) }
   .data :
   {
+   _data = .;
    *(.sdata)
    *(.data)
    *(.data1)

gnuefi/elf_ia32_efi.lds

@@ -9,13 +9,18 @@ SECTIONS
   . = ALIGN(4096);
   .text :
   {
+   _text = .;
    *(.text)
    *(.text.*)
    *(.gnu.linkonce.t.*)
+   . = ALIGN(16);
   }
+  _etext = .;
+  _text_size = . - _text;
   . = ALIGN(4096);
   .sdata :
   {
+   _data = .;
    *(.got.plt)
    *(.got)
    *(.srodata)
@@ -55,6 +60,8 @@ SECTIONS
     *(.data.rel.ro)
     *(.data.rel*)
   }
+  _edata = .;
+  _data_size = . - _etext;
   . = ALIGN(4096);
   .reloc :		/* This is the PECOFF .reloc section! */
   {

gnuefi/elf_ia32_fbsd_efi.lds

@@ -9,13 +9,18 @@ SECTIONS
   . = ALIGN(4096);
   .text :
   {
+   _text = .;
    *(.text)
    *(.text.*)
    *(.gnu.linkonce.t.*)
+   . = ALIGN(16);
   }
+  _etext = .;
+  _text_size = . - _text;
   . = ALIGN(4096);
   .sdata :
   {
+   _data = .;
    *(.got.plt)
    *(.got)
    *(.srodata)
@@ -55,6 +60,8 @@ SECTIONS
     *(.data.rel.ro)
     *(.data.rel*)
   }
+  _edata = .;
+  _data_size = . - _etext;
   . = ALIGN(4096);
   .reloc :		/* This is the PECOFF .reloc section! */
   {

gnuefi/elf_ia64_efi.lds

@@ -9,14 +9,19 @@ SECTIONS
   . = ALIGN(4096);
   .text :
   {
+   _text = .;
    *(.text)
    *(.text.*)
    *(.gnu.linkonce.t.*)
+   . = ALIGN(16);
   }
+  _etext = .;
+  _text_size = . - _text;
   . = ALIGN(4096);
   __gp = ALIGN (8) + 0x200000;
   .sdata :
   {
+   _data = .;
    *(.got.plt)
    *(.got)
    *(.srodata)
@@ -51,6 +56,8 @@ SECTIONS
     *(.rela.stab)
     *(.rela.ctors)
   }
+  _edata = .;
+  _data_size = . - _etext;
   . = ALIGN(4096);
   .reloc :		/* This is the PECOFF .reloc section! */
   {

gnuefi/elf_x86_64_efi.lds

@@ -15,10 +15,14 @@ SECTIONS
   . = ALIGN(4096);
   .text :
   {
+   _text = .;
    *(.text)
    *(.text.*)
    *(.gnu.linkonce.t.*)
+   . = ALIGN(16);
   }
+  _etext = .;
+  _text_size = . - _text;
   . = ALIGN(4096);
   .reloc :
   {
@@ -27,6 +31,7 @@ SECTIONS
   . = ALIGN(4096);
   .data :
   {
+   _data = .;
    *(.rodata*)
    *(.got.plt)
    *(.got)
@@ -41,6 +46,8 @@ SECTIONS
    *(COMMON)
    *(.rel.local)
   }
+  _edata = .;
+  _data_size = . - _etext;
   . = ALIGN(4096);
   .dynamic  : { *(.dynamic) }
   . = ALIGN(4096);

gnuefi/elf_x86_64_fbsd_efi.lds

@@ -15,8 +15,12 @@ SECTIONS
   . = ALIGN(4096);
   .text :
   {
+   _text = .;
    *(.text)
+   . = ALIGN(16);
   }
+  _etext = .;
+  _text_size = . - _text;
   .reloc :
   {
    *(.reloc)
@@ -24,6 +28,7 @@ SECTIONS
   . = ALIGN(4096);
   .data :
   {
+   _data = .;
    *(.rodata*)
    *(.got.plt)
    *(.got)
@@ -47,6 +52,8 @@ SECTIONS
     *(.rela.got)
     *(.rela.stab)
   }
+  _edata = .;
+  _data_size = . - _etext;
   . = ALIGN(4096);
   .dynsym   : { *(.dynsym) }
   . = ALIGN(4096);