Re: port-amd64/54775 (PXE netboot fails again)

[Emmanuel Dreyfus <manu%netbsd.org@localhost>]

The following reply was made to PR port-amd64/54775; it has been noted by GNATS.

From: Emmanuel Dreyfus <manu%netbsd.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: port-amd64/54775 (PXE netboot fails again)
Date: Mon, 23 Dec 2019 01:54:24 +0000

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 After a few exchange off-gnats with Andreas, we came to the conclusion
 that pxeboot_ia32.bin is confused by the presence of the empty multiboot
 section in the kernel. 
 
 If we enable options MULTIBOOT, the section is not empty anymore and the
 bug vanishes. And if we apply the attached patch, which makes the section
 non-empty when options MULTIBOOT is not enabled, the bug is fixed too.
 
 I will commit the fix nex sunday (I am away from my keys until then).
 
 -- 
 Emmanuel Dreyfus
 manu%netbsd.org@localhost
 
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 Index: sys/arch/amd64/amd64/locore.S
 ===================================================================
 RCS file: /cvsroot/src/sys/arch/amd64/amd64/locore.S,v
 retrieving revision 1.195
 diff -U4 -r1.195 locore.S
 --- sys/arch/amd64/amd64/locore.S	15 Dec 2019 02:58:21 -0000	1.195
 +++ sys/arch/amd64/amd64/locore.S	22 Dec 2019 02:23:11 -0000
 @@ -432,10 +432,10 @@
  	.space	512
  tmpstk:
  
  .section multiboot,"a"
 -#if defined(MULTIBOOT)
  	.align	8
 +#if defined(MULTIBOOT)
  	.globl	Multiboot2_Header
  _C_LABEL(Multiboot2_Header):
  	.int	MULTIBOOT2_HEADER_MAGIC
  	.int	MULTIBOOT2_ARCHITECTURE_I386
 @@ -473,8 +473,11 @@
  	.int	8	/* sizeof(struct multiboot_tag) */
  	.align	8
  	.globl	Multiboot2_Header_end
  _C_LABEL(Multiboot2_Header_end):
 +#else /* MULTIBOOT */
 +	.int	0xdeadbeef	/* have some non empty content */
 +	.align	8
  #endif	/* MULTIBOOT */
  
  /*
   * Some hackage to deal with 64bit symbols in 32 bit mode.
 
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