On Jul 25, 2014, at 4:07 AM, Varad Gautam <varadgautam@gmail.com> wrote:

The same problem appears when I build BeagleBoardPkg:
AutoGen.* contains proper PCDs, so does the build report. Yet, objdump
shows PcdGet calls to return 0.
-objdump snippets-
ArmPlatformPrePiUnicore.lib:
FixedPcdGet32 (PcdFdBaseAddress);
5e: f04f 2080 mov.w r0, #2147516416 ; 0x80008000
62: f7ff fffe bl 0 <PrePiMain>
...
StacksSize = PcdGet32 (PcdCPUCorePrimaryStackSize);
bc: 4b6e ldr r3, [pc, #440] ; (278 <PrePiMain+0x278>)
be: 681b ldr r3, [r3, #0]
c0: 9325 str r3, [sp, #148] ; 0x94

This looks like a GOT load. The address pc+440 is the address of the pointer to the global. What does pc+440 point to?

Maybe your toolchain is having an issue with GOT?

Thanks,

Andrew Fish

PS If you reference a global you were not compiled with, but linked with it becomes an indirect access.

this is clang, but you get the idea (I used armv6 as armv7 emits movw/movt). The linker would patch L_global$non_lazy_ptr with a pointer to the global at link time.

~/work/Compiler>cat got.c

extern int global;

int test()

{

  return global;

}

~/work/Compiler>clang -arch armv6 -Os -S got.c

~/work/Compiler>cat got.S

	.section	__TEXT,__text,regular,pure_instructions

	.section	__TEXT,__textcoal_nt,coalesced,pure_instructions

	.section	__TEXT,__const_coal,coalesced

	.section	__TEXT,__picsymbolstub4,symbol_stubs,none,16

	.section	__TEXT,__StaticInit,regular,pure_instructions

	.section	__TEXT,__cstring,cstring_literals

	.syntax unified

	.section	__TEXT,__text,regular,pure_instructions

	.globl	_test

	.align	2

_test:                                  @ @test

@ BB#0:

	ldr	r0, LCPI0_0

LPC0_0:

	ldr	r0, [pc, r0]

	ldr	r0, [r0]

	bx	lr

	.align	2

@ BB#1:

	.data_region

LCPI0_0:

	.long	L_global$non_lazy_ptr-(LPC0_0+8)

	.end_data_region

	.section	__DATA,__nl_symbol_ptr,non_lazy_symbol_pointers

	.align	2

L_global$non_lazy_ptr:

	.indirect_symbol	_global

	.long	0

.subsections_via_symbols

I have tried using a different toolchain :). What else is possible? I am looking into
the BaseTools build process. Could someone please verify this for BeagleBoardPkg?

Thanks,
Varad