[PATCH 0/7] VGA BIOS patches

[PATCH 0/7] VGA BIOS patches

[Frediano Ziglio]

There are a could of patch to vgabios code that
 - make some optimizations
 - fix a overflow computing frame buffer size
 - make Windows 8 suport greater resolutions
 - fix some informations returned from interrupt

Frediano Ziglio (7):
  vgabios: Output to Qemu debug port instead of using Bochs one
  vgabios: Does not define cur_mode if not required
  vgabios: Fix size computation overflow
  vgabios: Report mode not supported getting mode informations
  vgabios: Reduce stack usage getting mode informations
  vgabios: Check if mode is currently supported as vesa specifications
  vgabios: Make Windows 8 support greater resolutions

 tools/firmware/vgabios/vbe.c     |   69 +++++++++++++++++++++++++++++---------
 tools/firmware/vgabios/vgabios.c |    6 ++--
 2 files changed, 56 insertions(+), 19 deletions(-)

-- 
1.7.5.4

[PATCH 1/7] vgabios: Output to Qemu debug port instead of using Bochs one

[Frediano Ziglio]

Bios was outputing into port 0xe9 while Qemu use 0x12

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
---
 tools/firmware/vgabios/vgabios.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/firmware/vgabios/vgabios.c b/tools/firmware/vgabios/vgabios.c
index a9dbe00..e0b1ed9 100644
--- a/tools/firmware/vgabios/vgabios.c
+++ b/tools/firmware/vgabios/vgabios.c
@@ -3811,9 +3811,9 @@ void printf(s)
         for (i=0; i<format_width; i++) {
           nibble = (arg >> (4 * digit)) & 0x000f;
           if (nibble <= 9)
-            outb(0xe9, nibble + '0');
+            outb(0x12, nibble + '0');
           else
-            outb(0xe9, (nibble - 10) + 'A');
+            outb(0x12, (nibble - 10) + 'A');
           digit--;
           }
         in_format = 0;
@@ -3823,7 +3823,7 @@ void printf(s)
       //  }
       }
     else {
-      outb(0xe9, c);
+      outb(0x12, c);
       }
     s ++;
     }
-- 
1.7.5.4

[PATCH 2/7] vgabios: Does not define cur_mode if not required

[Frediano Ziglio]

Declare and use cur_mode only if debug is enabled

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
---
 tools/firmware/vgabios/vbe.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
index 3fc786d..3d42216 100644
--- a/tools/firmware/vgabios/vbe.c
+++ b/tools/firmware/vgabios/vbe.c
@@ -761,7 +761,9 @@ Bit16u *AX;Bit16u ES;Bit16u DI;
         Bit16u            status;
         Bit16u            result;
         Bit16u            vbe2_info;
+#ifdef DEBUG
         Bit16u            cur_mode=0;
+#endif
         Bit16u            cur_ptr=34;
         ModeInfoListItem  *cur_info=&mode_info_list;
         
@@ -849,9 +851,9 @@ Bit16u *AX;Bit16u ES;Bit16u DI;
                     (cur_info->info.XResolution * cur_info->info.XResolution * cur_info->info.BitsPerPixel <= vbe_info_block.TotalMemory << 19 )) {
 #ifdef DEBUG
                   printf("VBE found mode %x => %x\n", cur_info->mode,cur_mode);
+                  cur_mode++;
 #endif
                   write_word(ES, DI + cur_ptr, cur_info->mode);
-                  cur_mode++;
                   cur_ptr+=2;
                 } else {
 #ifdef DEBUG
-- 
1.7.5.4

[PATCH 3/7] vgabios: Fix size computation overflow

[Frediano Ziglio]

Remove an overflow computing width x height x bit which does
not fit into a 16 bits. I wrote a routine to multiple these value
and get the size required for framebuffer in segment unit (64k).

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
---
 tools/firmware/vgabios/vbe.c |   30 ++++++++++++++++++++++++++++--
 1 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
index 3d42216..35d9866 100644
--- a/tools/firmware/vgabios/vbe.c
+++ b/tools/firmware/vgabios/vbe.c
@@ -742,6 +742,29 @@ no_vbe_flag:
   jmp  _display_string
 ASM_END  
 
+ASM_START
+_size64:
+  push bp
+  mov  bp, sp
+  push dx
+
+; multiply bbp by yres first as results fit in 16bits
+; then multiply by xres
+  mov  ax, 8[bp]
+  mul  word 6[bp]
+  mul  word 4[bp]
+; divide by 2^19 ceiling result
+  add  ax, #0xffff
+  adc  dx, #7
+  mov  ax, dx
+  shr  ax, #3
+
+  pop  dx
+  pop  bp
+  ret
+ASM_END
+
+
 /** Function 00h - Return VBE Controller Information
  * 
  * Input:
@@ -846,9 +869,12 @@ Bit16u *AX;Bit16u ES;Bit16u DI;
                 
         do
         {
+                Bit16u size_64k = size64(cur_info->info.XResolution, cur_info->info.YResolution, cur_info->info.BitsPerPixel);
+                Bit16u max_bpp = dispi_get_max_bpp();
+
                 if ((cur_info->info.XResolution <= dispi_get_max_xres()) &&
-                    (cur_info->info.BitsPerPixel <= dispi_get_max_bpp()) &&
-                    (cur_info->info.XResolution * cur_info->info.XResolution * cur_info->info.BitsPerPixel <= vbe_info_block.TotalMemory << 19 )) {
+                    (cur_info->info.BitsPerPixel <= max_bpp) &&
+                    (size_64k <= vbe_info_block.TotalMemory)) {
 #ifdef DEBUG
                   printf("VBE found mode %x => %x\n", cur_info->mode,cur_mode);
                   cur_mode++;
-- 
1.7.5.4

[PATCH 4/7] vgabios: Report mode not supported getting mode informations

[Frediano Ziglio]

If you try to get mode information for an unsupported mode
interrupt should return error but not that the function is not
supported.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
---
 tools/firmware/vgabios/vbe.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
index 35d9866..fff314e 100644
--- a/tools/firmware/vgabios/vbe.c
+++ b/tools/firmware/vgabios/vbe.c
@@ -911,7 +911,8 @@ Bit16u *AX;Bit16u ES;Bit16u DI;
 void vbe_biosfn_return_mode_information(AX, CX, ES, DI)
 Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
 {
-        Bit16u            result=0x0100;
+        // error by default is 0x014f which means supported but error
+        Bit16u                 result=0x014f;
         Bit16u            ss=get_SS();
         ModeInfoBlock     info;
         ModeInfoListItem  *cur_info;
@@ -955,7 +956,6 @@ Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
 #ifdef DEBUG
                 printf("VBE *NOT* found mode %x\n",CX);
 #endif
-                result = 0x100;
         }
         
         if (result == 0x4f)
-- 
1.7.5.4

[PATCH 5/7] vgabios: Reduce stack usage getting mode informations

[Frediano Ziglio]

Informations are stored in a structure that is smaller than final one.
Previous code copy this structure to stack extending with zeroes then
update it and copy to caller while now the not-extended version is
copied into stack and then is extended during copy reducing stack
usage.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
---
 tools/firmware/vgabios/vbe.c |   13 +++++--------
 1 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
index fff314e..0b8b736 100644
--- a/tools/firmware/vgabios/vbe.c
+++ b/tools/firmware/vgabios/vbe.c
@@ -914,9 +914,9 @@ Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
         // error by default is 0x014f which means supported but error
         Bit16u                 result=0x014f;
         Bit16u            ss=get_SS();
-        ModeInfoBlock     info;
         ModeInfoListItem  *cur_info;
         Boolean           using_lfb;
+        ModeInfoBlockCompact   info;
 
 #ifdef DEBUG
         printf("VBE vbe_biosfn_return_mode_information ES%x DI%x CX%x\n",ES,DI,CX);
@@ -933,7 +933,6 @@ Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
 #ifdef DEBUG
                 printf("VBE found mode %x\n",CX);
 #endif        
-                memsetb(ss, &info, 0, sizeof(ModeInfoBlock));
                 memcpyb(ss, &info, 0xc000, &(cur_info->info), sizeof(ModeInfoBlockCompact));
                 if (using_lfb) {
                   info.NumberOfBanks = 1;
@@ -950,6 +949,10 @@ Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
                 info.PhysBasePtr |= inw(VBE_DISPI_IOPORT_DATA);
 #endif 							
                 result = 0x4f;
+
+                // copy updates in mode_info_block back
+                memsetb(ES, DI, 0, sizeof(ModeInfoBlock));
+                memcpyb(ES, DI, ss, &info, sizeof(info));
         }
         else
         {
@@ -957,12 +960,6 @@ Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
                 printf("VBE *NOT* found mode %x\n",CX);
 #endif
         }
-        
-        if (result == 0x4f)
-        {
-                // copy updates in mode_info_block back
-                memcpyb(ES, DI, ss, &info, sizeof(info));
-        }
 
         write_word(ss, AX, result);
 }
-- 
1.7.5.4

[PATCH 6/7] vgabios: Check if mode is currently supported as vesa specifications

[Frediano Ziglio]

Vesa specification require that mode information return if a given mode
is supported or not so test if we can support it checking required memory
and set correctly supported bit.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
---
 tools/firmware/vgabios/vbe.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
index 0b8b736..a7b06b9 100644
--- a/tools/firmware/vgabios/vbe.c
+++ b/tools/firmware/vgabios/vbe.c
@@ -930,10 +930,22 @@ Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
 
         if (cur_info != 0)
         {
+                Bit16u max_bpp = dispi_get_max_bpp();
+                Bit16u size_64k;
+                Bit16u totalMemory;
+
+                outw(VBE_DISPI_IOPORT_INDEX, VBE_DISPI_INDEX_VIDEO_MEMORY_64K);
+                totalMemory = inw(VBE_DISPI_IOPORT_DATA);
 #ifdef DEBUG
                 printf("VBE found mode %x\n",CX);
 #endif        
                 memcpyb(ss, &info, 0xc000, &(cur_info->info), sizeof(ModeInfoBlockCompact));
+                size_64k = size64(info.XResolution, info.YResolution, info.BitsPerPixel);
+                if ((info.XResolution > dispi_get_max_xres()) ||
+                    (info.BitsPerPixel > max_bpp) ||
+                    (size_64k > totalMemory))
+                  info.ModeAttributes &= ~VBE_MODE_ATTRIBUTE_SUPPORTED;
+
                 if (using_lfb) {
                   info.NumberOfBanks = 1;
                 }
-- 
1.7.5.4

[PATCH 7/7] vgabios: Make Windows 8 support greater resolutions

[Frediano Ziglio]

Apparently Windows 8 refuse to use any mode if has more than one page.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
---
 tools/firmware/vgabios/vbe.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
index a7b06b9..9131721 100644
--- a/tools/firmware/vgabios/vbe.c
+++ b/tools/firmware/vgabios/vbe.c
@@ -946,9 +946,9 @@ Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
                     (size_64k > totalMemory))
                   info.ModeAttributes &= ~VBE_MODE_ATTRIBUTE_SUPPORTED;
 
-                if (using_lfb) {
-                  info.NumberOfBanks = 1;
-                }
+                /* Windows 8 require this to be 1! */
+                info.NumberOfBanks = 1;
+
                 if (info.WinAAttributes & VBE_WINDOW_ATTRIBUTE_RELOCATABLE) {
                   info.WinFuncPtr = 0xC0000000UL;
                   *(Bit16u *)&(info.WinFuncPtr) = (Bit16u)(dispi_set_bank_farcall);
-- 
1.7.5.4

Re: [PATCH 1/7] vgabios: Output to Qemu debug port instead of using Bochs one

[Ian Campbell]

On Fri, 2012-05-04 at 13:36 +0100, Frediano Ziglio wrote:
> Bios was outputing into port 0xe9 while Qemu use 0x12

0xe9 is also the Xen HVM debug port (see hvm_print_line), don't be
confused by the fact that it happens to be the same as the bochs port.

Ian.

> Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
> ---
>  tools/firmware/vgabios/vgabios.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/firmware/vgabios/vgabios.c b/tools/firmware/vgabios/vgabios.c
> index a9dbe00..e0b1ed9 100644
> --- a/tools/firmware/vgabios/vgabios.c
> +++ b/tools/firmware/vgabios/vgabios.c
> @@ -3811,9 +3811,9 @@ void printf(s)
>          for (i=0; i<format_width; i++) {
>            nibble = (arg >> (4 * digit)) & 0x000f;
>            if (nibble <= 9)
> -            outb(0xe9, nibble + '0');
> +            outb(0x12, nibble + '0');
>            else
> -            outb(0xe9, (nibble - 10) + 'A');
> +            outb(0x12, (nibble - 10) + 'A');
>            digit--;
>            }
>          in_format = 0;
> @@ -3823,7 +3823,7 @@ void printf(s)
>        //  }
>        }
>      else {
> -      outb(0xe9, c);
> +      outb(0x12, c);
>        }
>      s ++;
>      }

Re: [PATCH 3/7] vgabios: Fix size computation overflow

[Ian Campbell]

On Fri, 2012-05-04 at 13:36 +0100, Frediano Ziglio wrote:
> Remove an overflow computing width x height x bit which does
> not fit into a 16 bits. I wrote a routine to multiple these value
> and get the size required for framebuffer in segment unit (64k).

Couldn't this be done in C using a suitably wide temporary variable?

> 
> Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
> ---
>  tools/firmware/vgabios/vbe.c |   30 ++++++++++++++++++++++++++++--
>  1 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
> index 3d42216..35d9866 100644
> --- a/tools/firmware/vgabios/vbe.c
> +++ b/tools/firmware/vgabios/vbe.c
> @@ -742,6 +742,29 @@ no_vbe_flag:
>    jmp  _display_string
>  ASM_END  
>  
> +ASM_START
> +_size64:
> +  push bp
> +  mov  bp, sp
> +  push dx
> +
> +; multiply bbp by yres first as results fit in 16bits
> +; then multiply by xres
> +  mov  ax, 8[bp]
> +  mul  word 6[bp]
> +  mul  word 4[bp]
> +; divide by 2^19 ceiling result
> +  add  ax, #0xffff
> +  adc  dx, #7
> +  mov  ax, dx
> +  shr  ax, #3
> +
> +  pop  dx
> +  pop  bp
> +  ret
> +ASM_END
> +
> +
>  /** Function 00h - Return VBE Controller Information
>   * 
>   * Input:
> @@ -846,9 +869,12 @@ Bit16u *AX;Bit16u ES;Bit16u DI;
>                  
>          do
>          {
> +                Bit16u size_64k = size64(cur_info->info.XResolution, cur_info->info.YResolution, cur_info->info.BitsPerPixel);
> +                Bit16u max_bpp = dispi_get_max_bpp();
> +
>                  if ((cur_info->info.XResolution <= dispi_get_max_xres()) &&
> -                    (cur_info->info.BitsPerPixel <= dispi_get_max_bpp()) &&
> -                    (cur_info->info.XResolution * cur_info->info.XResolution * cur_info->info.BitsPerPixel <= vbe_info_block.TotalMemory << 19 )) {
> +                    (cur_info->info.BitsPerPixel <= max_bpp) &&
> +                    (size_64k <= vbe_info_block.TotalMemory)) {
>  #ifdef DEBUG
>                    printf("VBE found mode %x => %x\n", cur_info->mode,cur_mode);
>                    cur_mode++;

Re: [PATCH 3/7] vgabios: Fix size computation overflow

[Frediano Ziglio]

On Fri, 2012-05-04 at 15:12 +0100, Ian Campbell wrote:
> On Fri, 2012-05-04 at 13:36 +0100, Frediano Ziglio wrote:
> > Remove an overflow computing width x height x bit which does
> > not fit into a 16 bits. I wrote a routine to multiple these value
> > and get the size required for framebuffer in segment unit (64k).
> 
> Couldn't this be done in C using a suitably wide temporary variable?
> 

I'd like :(

BCC compiler used need some function which are not linked by BIOS.

Personally I would switch to something more clever like OpenWatcom but
mainly I wrote some small asm.

I think bochs code fix the issue providing a asm function used by
compiler but seems more hacky than my function.

Frediano

> > 
> > Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
> > ---
> >  tools/firmware/vgabios/vbe.c |   30 ++++++++++++++++++++++++++++--
> >  1 files changed, 28 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
> > index 3d42216..35d9866 100644
> > --- a/tools/firmware/vgabios/vbe.c
> > +++ b/tools/firmware/vgabios/vbe.c
> > @@ -742,6 +742,29 @@ no_vbe_flag:
> >    jmp  _display_string
> >  ASM_END  
> >  
> > +ASM_START
> > +_size64:
> > +  push bp
> > +  mov  bp, sp
> > +  push dx
> > +
> > +; multiply bbp by yres first as results fit in 16bits
> > +; then multiply by xres
> > +  mov  ax, 8[bp]
> > +  mul  word 6[bp]
> > +  mul  word 4[bp]
> > +; divide by 2^19 ceiling result
> > +  add  ax, #0xffff
> > +  adc  dx, #7
> > +  mov  ax, dx
> > +  shr  ax, #3
> > +
> > +  pop  dx
> > +  pop  bp
> > +  ret
> > +ASM_END
> > +
> > +
> >  /** Function 00h - Return VBE Controller Information
> >   * 
> >   * Input:
> > @@ -846,9 +869,12 @@ Bit16u *AX;Bit16u ES;Bit16u DI;
> >                  
> >          do
> >          {
> > +                Bit16u size_64k = size64(cur_info->info.XResolution, cur_info->info.YResolution, cur_info->info.BitsPerPixel);
> > +                Bit16u max_bpp = dispi_get_max_bpp();
> > +
> >                  if ((cur_info->info.XResolution <= dispi_get_max_xres()) &&
> > -                    (cur_info->info.BitsPerPixel <= dispi_get_max_bpp()) &&
> > -                    (cur_info->info.XResolution * cur_info->info.XResolution * cur_info->info.BitsPerPixel <= vbe_info_block.TotalMemory << 19 )) {
> > +                    (cur_info->info.BitsPerPixel <= max_bpp) &&
> > +                    (size_64k <= vbe_info_block.TotalMemory)) {
> >  #ifdef DEBUG
> >                    printf("VBE found mode %x => %x\n", cur_info->mode,cur_mode);
> >                    cur_mode++;
> 
> 

Re: [PATCH 4/7] vgabios: Report mode not supported getting mode informations

[Ian Campbell]

On Fri, 2012-05-04 at 13:36 +0100, Frediano Ziglio wrote:
> If you try to get mode information for an unsupported mode
> interrupt should return error but not that the function is not
> supported.
> 
> Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
> ---
>  tools/firmware/vgabios/vbe.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
> index 35d9866..fff314e 100644
> --- a/tools/firmware/vgabios/vbe.c
> +++ b/tools/firmware/vgabios/vbe.c
> @@ -911,7 +911,8 @@ Bit16u *AX;Bit16u ES;Bit16u DI;
>  void vbe_biosfn_return_mode_information(AX, CX, ES, DI)
>  Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
>  {
> -        Bit16u            result=0x0100;
> +        // error by default is 0x014f which means supported but error
> +        Bit16u                 result=0x014f;

Something odd has happened to the whitepace here. Otherwise:
Acked-by: Ian Campbell <ian.campbell@citrix.com>


>          Bit16u            ss=get_SS();
>          ModeInfoBlock     info;
>          ModeInfoListItem  *cur_info;
> @@ -955,7 +956,6 @@ Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
>  #ifdef DEBUG
>                  printf("VBE *NOT* found mode %x\n",CX);
>  #endif
> -                result = 0x100;
>          }
>          
>          if (result == 0x4f)

Re: [PATCH 7/7] vgabios: Make Windows 8 support greater resolutions

[Ian Campbell]

On Fri, 2012-05-04 at 13:36 +0100, Frediano Ziglio wrote:
> Apparently Windows 8 refuse to use any mode if has more than one page.

What about OSes other than Windows 8? Did you test with any of them?

> 
> Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
> ---
>  tools/firmware/vgabios/vbe.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/firmware/vgabios/vbe.c b/tools/firmware/vgabios/vbe.c
> index a7b06b9..9131721 100644
> --- a/tools/firmware/vgabios/vbe.c
> +++ b/tools/firmware/vgabios/vbe.c
> @@ -946,9 +946,9 @@ Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
>                      (size_64k > totalMemory))
>                    info.ModeAttributes &= ~VBE_MODE_ATTRIBUTE_SUPPORTED;
>  
> -                if (using_lfb) {
> -                  info.NumberOfBanks = 1;
> -                }
> +                /* Windows 8 require this to be 1! */
> +                info.NumberOfBanks = 1;
> +
>                  if (info.WinAAttributes & VBE_WINDOW_ATTRIBUTE_RELOCATABLE) {
>                    info.WinFuncPtr = 0xC0000000UL;
>                    *(Bit16u *)&(info.WinFuncPtr) = (Bit16u)(dispi_set_bank_farcall);

Re: [PATCH 3/7] vgabios: Fix size computation overflow

[Ian Campbell]

On Fri, 2012-05-04 at 15:18 +0100, Frediano Ziglio wrote:
> On Fri, 2012-05-04 at 15:12 +0100, Ian Campbell wrote:
> > On Fri, 2012-05-04 at 13:36 +0100, Frediano Ziglio wrote:
> > > Remove an overflow computing width x height x bit which does
> > > not fit into a 16 bits. I wrote a routine to multiple these value
> > > and get the size required for framebuffer in segment unit (64k).
> > 
> > Couldn't this be done in C using a suitably wide temporary variable?
> > 
> 
> I'd like :(
> 
> BCC compiler used need some function which are not linked by BIOS.

In which case 

Acked-by: Ian Campbell <ian.campbell@citrix.com>

Re: [PATCH 3/7] vgabios: Fix size computation overflow

[Frediano Ziglio]

On Fri, 2012-05-04 at 15:26 +0100, Ian Campbell wrote:
> On Fri, 2012-05-04 at 15:18 +0100, Frediano Ziglio wrote:
> > On Fri, 2012-05-04 at 15:12 +0100, Ian Campbell wrote:
> > > On Fri, 2012-05-04 at 13:36 +0100, Frediano Ziglio wrote:
> > > > Remove an overflow computing width x height x bit which does
> > > > not fit into a 16 bits. I wrote a routine to multiple these value
> > > > and get the size required for framebuffer in segment unit (64k).
> > > 
> > > Couldn't this be done in C using a suitably wide temporary variable?
> > > 
> > 
> > I'd like :(
> > 
> > BCC compiler used need some function which are not linked by BIOS.
> 
> In which case 
> 
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
> 
> 

In current vgabios (from Bochs not Xen copy) size is computed using 


size_64k = (Bit16u)((Bit32u)cur_info->info.XResolution * cur_info->info.XResolution * cur_info->info.BitsPerPixel) >> 19;


If you try to use this code you get an undefined call to lmulul. Bochs
code (still in vbe.c) provide this internal function with this asm code:


; helper function for memory size calculation

lmulul:
  and eax, #0x0000FFFF
  shl ebx, #16
  or  eax, ebx
  SEG SS
  mul eax, dword ptr [di]
  mov ebx, eax
  shr ebx, #16
  ret


Note also that Bochs line have some problems
- it multiply Xres by Xres intead of Xres by Yref
- it does not take into account ceiling division

Frediano

Re: [PATCH 3/7] vgabios: Fix size computation overflow

[Frediano Ziglio]

On Fri, 2012-05-04 at 15:26 +0100, Ian Campbell wrote:
> On Fri, 2012-05-04 at 15:18 +0100, Frediano Ziglio wrote:
> > On Fri, 2012-05-04 at 15:12 +0100, Ian Campbell wrote:
> > > On Fri, 2012-05-04 at 13:36 +0100, Frediano Ziglio wrote:
> > > > Remove an overflow computing width x height x bit which does
> > > > not fit into a 16 bits. I wrote a routine to multiple these value
> > > > and get the size required for framebuffer in segment unit (64k).
> > > 
> > > Couldn't this be done in C using a suitably wide temporary variable?
> > > 
> > 
> > I'd like :(
> > 
> > BCC compiler used need some function which are not linked by BIOS.
> 
> In which case 
> 
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
> 
> 

In current vgabios (from Bochs not Xen copy) size is computed using 


size_64k = (Bit16u)((Bit32u)cur_info->info.XResolution * cur_info->info.XResolution * cur_info->info.BitsPerPixel) >> 19;


If you try to use this code you get an undefined call to lmulul. Bochs
code (still in vbe.c) provide this internal function with this asm code:


; helper function for memory size calculation

lmulul:
  and eax, #0x0000FFFF
  shl ebx, #16
  or  eax, ebx
  SEG SS
  mul eax, dword ptr [di]
  mov ebx, eax
  shr ebx, #16
  ret


Note also that Bochs line have some problems
- it multiply Xres by Xres intead of Xres by Yref
- it does not take into account ceiling division

Frediano

Re: [PATCH 3/7] vgabios: Fix size computation overflow

[Frediano Ziglio]

On Fri, 2012-05-04 at 15:26 +0100, Ian Campbell wrote:
> On Fri, 2012-05-04 at 15:18 +0100, Frediano Ziglio wrote:
> > On Fri, 2012-05-04 at 15:12 +0100, Ian Campbell wrote:
> > > On Fri, 2012-05-04 at 13:36 +0100, Frediano Ziglio wrote:
> > > > Remove an overflow computing width x height x bit which does
> > > > not fit into a 16 bits. I wrote a routine to multiple these value
> > > > and get the size required for framebuffer in segment unit (64k).
> > > 
> > > Couldn't this be done in C using a suitably wide temporary variable?
> > > 
> > 
> > I'd like :(
> > 
> > BCC compiler used need some function which are not linked by BIOS.
> 
> In which case 
> 
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
> 
> 

In current vgabios (from Bochs not Xen copy) size is computed using 


size_64k = (Bit16u)((Bit32u)cur_info->info.XResolution * cur_info->info.XResolution * cur_info->info.BitsPerPixel) >> 19;


If you try to use this code you get an undefined call to lmulul. Bochs
code (still in vbe.c) provide this internal function with this asm code:


; helper function for memory size calculation

lmulul:
  and eax, #0x0000FFFF
  shl ebx, #16
  or  eax, ebx
  SEG SS
  mul eax, dword ptr [di]
  mov ebx, eax
  shr ebx, #16
  ret


Note also that Bochs line have some problems
- it multiply Xres by Xres intead of Xres by Yref
- it does not take into account ceiling division

Frediano