[edk2] AArch64 Debugger Global Variable Correlation Issues

[Cohen, Eugene]

Dear ArmPkg maintainers,

I'm trying to debug AArch64 code built with Linaro GCC and don't have proper correlation for global variables.

I'm digging into how .data/.bss is correlated across ELF and PE-COFF and I see different offsets (in ELF the data appears to be 64KB higher up than PE-COFF). I'm also seeing warning in GenFw related to multiple ELF sections being squashed into one PE-COFF section.

I'm not an expert in the GNU linker configuration but it seems that if we could get the ELF and PE-COFF layouts to match that it would fix the debugger correlation.

Here's the GenFw output:
3> Convert c:\ecedk2\Build\ArmVExpress-FVP-AArch64\DEBUG_GCC49\AARCH64\MdeModulePkg\Core\PiSmmCore\PiSmmIpl\DEBUG\PiSmmIpl.dll from ELF to PE/COFF.
3> Check Elf Image Header
3> Set EHDR
3> Check ELF64 Header Information
3> Update Header Pointers
3> Create COFF Section Offset Buffer
3> Fill in Function Pointers
3> Compute sections new address.
3> GenFw: WARNING
3> Mulitple sections in c:\ecedk2\Build\ArmVExpress-FVP-AArch64\DEBUG_GCC49\AARCH64\MdeModulePkg\Core\PiSmmCore\PiSmmIpl\DEBUG\PiSmmIpl.dll are merged into 1 text section. Source level debug might not work correctly.
3> GenFw: WARNING
3> Mulitple sections in c:\ecedk2\Build\ArmVExpress-FVP-AArch64\DEBUG_GCC49\AARCH64\MdeModulePkg\Core\PiSmmCore\PiSmmIpl\DEBUG\PiSmmIpl.dll are merged into 1 data section. Source level debug might not work correctly.
3> Write and relocate sections.
3> Applying Relocations...
3> Applying Relocations

Here's the ELF layout for the module, notice how far out data starts (and with rodata which will be squashed into .text and .bss which will be squashed into .data)
Idx Name Size VMA LMA File off Algn
0 .text 00009c90 0000000000000000 0000000000000000 00010000 2**3
CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE
1 .rodata 00002458 0000000000009c90 0000000000009c90 00019c90 2**3
CONTENTS, ALLOC, LOAD, READONLY, DATA
2 .data 00000460 000000000001c0e8 000000000001c0e8 0001c0e8 2**3
CONTENTS, ALLOC, LOAD, RELOC, DATA
3 .bss 00000088 000000000001c548 000000000001c548 0001c548 2**3
ALLOC

And PE-COFF has data at a different offset with data much closer in:
SECTION HEADER #1
.text name
C100 virtual size
260 virtual address (0000000000000260 to 000000000000C35F)
C100 size of raw data

SECTION HEADER #2
.data name
500 virtual size
C360 virtual address (000000000000C360 to 000000000000C85F)
500 size of raw data

So we can see that the data offset from text is inconsistent between the two.

Thanks,

Eugene

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