RE: [Patch] Do not clear BSS region in x86 stub

[Shao, Marshall]

Hi Ard,

> Given that GRUB now supports the native EFI entrypoint properly, 
> the handover protocol is essentially deprecated.

In my case, the systemd-boot jumped into the EFI stub code via
handover protocol, this may not be an orthodox way to boot the kernel
but it performs well on the others, I have tested on at least 
6 firmware.

I understand that the handover protocol is going to be deprecated.
However, as of now, I can't guarantee which EFI loader will be 
used to load my bzImage. Although it’s not very common, booting 
from the handover protocol with uncleaned BSS memory is possible.

>> memset(_bss+0x10000, 0, _ebss - _bss - 0x10000)

> So now you are applying the memset only to part of BSS, right? How
> does this help?

This part doesn't work without increasing the BOOT_STACK_SIZE.

And following content is my PE metadata, many thanks!


File: bzImage
Format: COFF-x86-64
Arch: x86_64
AddressSize: 64bit
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  Characteristics [ (0x206)
    IMAGE_FILE_DEBUG_STRIPPED (0x200)
    IMAGE_FILE_EXECUTABLE_IMAGE (0x2)
    IMAGE_FILE_LINE_NUMS_STRIPPED (0x4)
  ]
}
ImageOptionalHeader {
  Magic: 0x20B
  MajorLinkerVersion: 2
  MinorLinkerVersion: 20
  SizeOfCode: 9416704
  SizeOfInitializedData: 241664
  SizeOfUninitializedData: 0
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  BaseOfCode: 0x4000
  ImageBase: 0x0
  SectionAlignment: 4096
  FileAlignment: 512
  MajorOperatingSystemVersion: 0
  MinorOperatingSystemVersion: 0
  MajorImageVersion: 3
  MinorImageVersion: 0
  MajorSubsystemVersion: 0
  MinorSubsystemVersion: 0
  SizeOfImage: 9674752
  SizeOfHeaders: 4096
  Subsystem: IMAGE_SUBSYSTEM_EFI_APPLICATION (0xA)
  Characteristics [ (0x100)
    IMAGE_DLL_CHARACTERISTICS_NX_COMPAT (0x100)
  ]
  SizeOfStackReserve: 0
  SizeOfStackCommit: 0
  SizeOfHeapReserve: 0
  SizeOfHeapCommit: 0
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    CertificateTableSize: 0x0
    BaseRelocationTableRVA: 0x0
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}
DOSHeader {
  Magic: MZ
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}
Sections [
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    Number: 1
    Name: .setup (2E 73 65 74 75 70 00 00)
    VirtualSize: 0x3000
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    RawDataSize: 12288
    PointerToRawData: 0x1000
    PointerToRelocations: 0x0
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    LineNumberCount: 0
    Characteristics [ (0x42000040)
      IMAGE_SCN_CNT_INITIALIZED_DATA (0x40)
      IMAGE_SCN_MEM_DISCARDABLE (0x2000000)
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  }
  Section {
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    Name: .text (2E 74 65 78 74 00 00 00)
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    RawDataSize: 9416704
    PointerToRawData: 0x4000
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    Characteristics [ (0x60000020)
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  Section {
    Number: 3
    Name: .data (2E 64 61 74 61 00 00 00)
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    Characteristics [ (0xC0000040)
      IMAGE_SCN_CNT_INITIALIZED_DATA (0x40)
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    ]
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Relocations [
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UnwindInformation [
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Symbols [
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