On Jul 25, 2014, at 4:07 AM, Varad Gautam <varadgau...@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
>
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