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includeos / IncludeOS

A minimal, resource efficient unikernel for cloud services
https://includeos.github.io/
Apache License 2.0
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Add back ELF symbols in stacktraces, add more tests #2264

Closed MagnusS closed 3 months ago

MagnusS commented 3 months ago

This PR adds back stacktraces with symbol information + adds tests. See commits for additional details.

The main change is adding __attribute__(section(".data")) to the static struct relocs used to store ELF metadata to make sure it's included in the ELF .data section (not BSS). This is needed to make sure that we don't overwrite parts of it when we initialise BSS.

On boot we first load the symbol table from .elf_symbols and move it to a new memory location. The new location of the symbol table is stored in relocs.syms: https://github.com/includeos/IncludeOS/blob/v0.16.0-release/src/kernel/elf.cpp#L350

We then initialise/clear the BSS area: https://github.com/includeos/IncludeOS/blob/v0.16.0-release/src/platform/x86_pc/kernel_start.cpp#L95

This previously had the side effect of setting relocs.syms back to 0 and we lost the new location of the ELF symbol table. The ELF parser initialised a few lines below would then fail.

fwsGonzo commented 3 months ago

That's a nice find.

alfreb commented 3 months ago

Excellent find - just finished testing - this will be super useful!