[Xen-devel] Re: [PATCH] rombios: move the stack to 0x9e000 and protect it with an e820 entry

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

Ooops - please don't apply this, it breaks CD-ROM boot. 

Cheers,

Tim.

At 16:35 +0100 on 06 Jul (1278434127), Tim Deegan wrote:
> rombios: move the stack to 0x9e000 and protect it with an e820 entry
> so that we don't corrupt E820_RAM memory with stack ops in S3 wakeup.
> It has to move up so the lowest contiguous RAM area is >= 512MiB.
> 
> This relies on the previous fix to let DS != SS
> 
> Signed-off-by: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
> Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
> 
> diff -r 4160103f98e3 tools/firmware/hvmloader/hvmloader.c
> --- a/tools/firmware/hvmloader/hvmloader.c    Tue Jul 06 16:27:22 2010 +0100
> +++ b/tools/firmware/hvmloader/hvmloader.c    Tue Jul 06 16:28:09 2010 +0100
> @@ -576,16 +576,64 @@
>      printf("vm86 TSS at %08lx\n", virt_to_phys(tss));
>  }
>  
> +static void dump_e820_table(void)
> +{
> +    struct e820entry *e820 = E820;
> +    unsigned int nr = *E820_NR;
> +    unsigned int last_end = 0;
> +    int i;
> +
> +    printf("E820 table:\n");
> +
> +    for (i = 0; i < nr; i++) {
> +        unsigned int start = e820[i].addr;
> +        unsigned int end = e820[i].addr + e820[i].size;
> +
> +        if (start < last_end)
> +            printf(" OVERLAP!!\n");
> +        else if (start > last_end)
> +            printf(" HOLE: %08x - %08x\n", last_end, start);
> +
> +        printf(" [%02d]: %08x - %08x: ", i, start, end);
> +        switch (e820[i].type) {
> +        case E820_RAM:
> +            printf("RAM\n");
> +            break;
> +        case E820_RESERVED:
> +            printf("RESERVED\n");
> +            break;
> +        case E820_ACPI:
> +            printf("ACPI\n");
> +            break;
> +        case E820_NVS:
> +            printf("NVS\n");
> +            break;
> +        default:
> +            printf("UNKNOWN (%08x)\n", e820[i].type);
> +            break;
> +        }
> +
> +        last_end = end;
> +    }
> +}
> +
>  /* Create an E820 table based on memory parameters provided in hvm_info. */
>  static void build_e820_table(void)
>  {
>      struct e820entry *e820 = E820;
>      unsigned int nr = 0;
>  
> -    /* 0x0-0x9FC00: Ordinary RAM. */
> -    e820[nr].addr = 0x0;
> -    e820[nr].size = 0x9FC00;
> +    /* 0x0-0x9EC00: Ordinary RAM. */
> +    /* (Must be at least 512K to keep Windows happy) */
> +    e820[nr].addr = 0x00000;
> +    e820[nr].size = 0x9E000;
>      e820[nr].type = E820_RAM;
> +    nr++;
> +
> +    /* 0x9E000-0x9FC00: Reserved for internal use. */
> +    e820[nr].addr = 0x9E000;
> +    e820[nr].size = 0x01C00;
> +    e820[nr].type = E820_RESERVED;
>      nr++;
>  
>      /* 0x9FC00-0xA0000: Extended BIOS Data Area (EBDA). */
> @@ -739,6 +787,7 @@
>                 ROMBIOS_PHYSICAL_ADDRESS + rombios_sz - 1);
>  
>      build_e820_table();
> +    dump_e820_table();
>  
>      bios_info = (struct bios_info *)BIOS_INFO_PHYSICAL_ADDRESS;
>      memset(bios_info, 0, sizeof(*bios_info));
> diff -r 4160103f98e3 tools/firmware/rombios/rombios.c
> --- a/tools/firmware/rombios/rombios.c        Tue Jul 06 16:27:22 2010 +0100
> +++ b/tools/firmware/rombios/rombios.c        Tue Jul 06 16:28:09 2010 +0100
> @@ -1,6 +1,6 @@
>  /////////////////////////////////////////////////////////////////////////
>  // $Id: rombios.c,v 1.221 2008/12/07 17:32:29 sshwarts Exp $
> -/////////////////////////////////////////////////////////////////////////
> +////////////////////////////#/////////////////////////////////////////////
>  //
>  //  Copyright (C) 2002  MandrakeSoft S.A.
>  //
> @@ -8871,13 +8871,14 @@
>  int18_handler: ;; Boot Failure recovery: try the next device.
>  
>    ;; Reset SP and SS
> -  mov  ax, #0xfffe
> +  mov  ax, #0x0ffe
>    mov  sp, ax
> -  xor  ax, ax
> +  mov  ax, #0x9e00
>    mov  ss, ax
>  
>    ;; The first time we do this it will have been set to -1 so 
>    ;; we will start from device 0.
> +  xor  ax, ax
>    mov  ds, ax
>    mov  bx, word ptr [0x40E]       ;; EBDA segment
>    mov  ds, bx                     ;; Set segment
> @@ -8911,9 +8912,9 @@
>    ;; 
>    ;; Reset SP and SS
>  
> -  mov  ax, #0xfffe
> +  mov  ax, #0x0ffe
>    mov  sp, ax
> -  xor  ax, ax
> +  mov  ax, #0x9e00
>    mov  ss, ax
>  
>    call _machine_reset
> @@ -10848,10 +10849,9 @@
>    ; case 0: normal startup
>  
>    cli
> -  mov  ax, #0xfffe
> +  mov  ax, #0x0ffe
>    mov  sp, ax
> -  xor  ax, ax
> -  mov  ds, ax
> +  mov  ax, #0x9e00
>    mov  ss, ax
>  
>    ;; Save shutdown status

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, XenServer Engineering
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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