linux-kernel - Re: [PATCH]x86_64: build and use GDT on copied compressed kernel

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Message-ID: <86802c440705122355r5f811d5bg2006b0b22ca885e6@mail.gmail.com>
Date:	Sat, 12 May 2007 23:55:34 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	"Andi Kleen" <ak@...e.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Vivek Goyal" <vgoyal@...ibm.com>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH]x86_64: build and use GDT on copied compressed kernel

On 5/12/07, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
> For data segments we never use that GDT, it is only for the code
> segment we use the GDT and that only to get us into 64bit mode.
>

after the patch
linux:/home/yhlu/xx/xx/kernel/linux-2.6/arch/x86_64/boot/compressed #
readelf -e vmlinux
...
Section Headers:
  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
  [ 0]                   NULL             0000000000000000  00000000
       0000000000000000  0000000000000000           0     0     0
  [ 1] .text             PROGBITS         0000000000000000  00100000
       000000000032617c  0000000000000000  AX       0     0     16
  [ 2] .rodata           PROGBITS         0000000000326180  00426180
       0000000000000400  0000000000000000   A       0     0     32
  [ 3] .eh_frame         PROGBITS         0000000000326580  00426580
       0000000000000210  0000000000000000   A       0     0     8
  [ 4] .data             PROGBITS         0000000000326790  00426790
       0000000000000008  0000000000000000  WA       0     0     8
  [ 5] .bss              NOBITS           00000000003267a0  00426798
       000000000000b860  0000000000000000  WA       0     0     32
  [ 6] .comment          PROGBITS         0000000000000000  00426798
       0000000000000035  0000000000000000           0     0     1
  [ 7] .shstrtab         STRTAB           0000000000000000  004267cd
       0000000000000047  0000000000000000           0     0     1
  [ 8] .symtab           SYMTAB           0000000000000000  00426a98
       00000000000007c8  0000000000000018           9    60     8
  [ 9] .strtab           STRTAB           0000000000000000  00427260
       0000000000000350  0000000000000000           0     0     1
Key to Flags:
  W (write), A (alloc), X (execute), M (merge), S (strings)
  I (info), L (link order), G (group), x (unknown)
  O (extra OS processing required) o (OS specific), p (processor specific)

after the patch, it seems .data section size still have 8 bytes.
before that will 0x28.
don't know what are the 8 bytes.

YH
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