Re: [ros-dev] [ros-diffs] [hbelusca] 66022: [FREELDR]: Commit a temporary "hackfix" for (Pc)GetTime: on VBox when booting with PXE, for some mysterious reason, Int386(0x1A) call with AH = 0x02 (Get CMOS Time) *never ever* r...

[Pierre Schweitzer]

From our investigations (Timo & I), there seems to be a memory
corruption when using a PXE boot on VBox.

You're committing a hack to workaround this memory corruption (which
replaces code which seems correct by some other code which is probably
correct), which lets you go a little bit further, where memory
corruption seems to strike again. And thus, this doesn't bring PXE boot
in better shape.

Furthermore, it appears that you're working around a bug which isn't in
ReactOS but in VBox. As a reminder, PXE boot works fine with Qemu, with
VMware. And when changing the ROM of VBox [1], then PXE boot works on
VBox as well.

Revert and report to VirtualBox instead. Our code is correct.

Thanks to Timo & Hervé for their help on digging into this issue.

[1]: https://git.ipxe.org/ipxe.git/blob/HEAD:/src/config/vbox/README

On 10/01/2015 01:21, hbelusca(a)svn.reactos.org wrote:
>   Author: hbelusca
>  Date: Sat Jan 10 00:21:33 2015
>  New Revision: 66022
>  
>  URL: http://svn.reactos.org/svn/reactos?rev=66022&view=rev
>  Log:
>  [FREELDR]: Commit a temporary "hackfix" for (Pc)GetTime: on VBox when booting
> with PXE, for some mysterious reason, Int386(0x1A) call with AH = 0x02 (Get CMOS Time)
> *never ever* returns!! (however without PXE everything works). So... is it some kind of
> stack overflow or whatever that makes the Int386 function stack messy? Or something else?
> So in the meantime we use direct CMOS port reads. Timo, Hervé (and others), can you please
> review? And in particular why does it happen only with PXE?
>  
>  Modified:
>      trunk/reactos/boot/freeldr/freeldr/arch/i386/pcrtc.c
>  
>  Modified: trunk/reactos/boot/freeldr/freeldr/arch/i386/pcrtc.c
>  URL:
> http://svn.reactos.org/svn/reactos/trunk/reactos/boot/freeldr/freeldr/arch/…
>  ==============================================================================
>  --- trunk/reactos/boot/freeldr/freeldr/arch/i386/pcrtc.c	[iso-8859-1] (original)
>  +++ trunk/reactos/boot/freeldr/freeldr/arch/i386/pcrtc.c	[iso-8859-1] Sat Jan 10 00:21:33
> 2015
>  @@ -20,10 +20,50 @@
>   
>   #define BCD_INT(bcd) (((bcd & 0xf0) >> 4) * 10 + (bcd &0x0f))
>   
>  +#ifndef INT386_WITH_INT_1A_AH_02_04__IS__FIXED
>  +
>  +/* CMOS Registers and Ports */
>  +#define CMOS_CONTROL_PORT       (PUCHAR)0x70
>  +#define CMOS_DATA_PORT          (PUCHAR)0x71
>  +
>  +#define RTC_REGISTER_A          0x0A
>  +#define   RTC_REG_A_UIP         0x80
>  +
>  +static UCHAR
>  +HalpReadCmos(IN UCHAR Reg)
>  +{
>  +    /* Select the register */
>  +    WRITE_PORT_UCHAR(CMOS_CONTROL_PORT, Reg);
>  +
>  +    /* Query the value */
>  +    return READ_PORT_UCHAR(CMOS_DATA_PORT);
>  +}
>  +
>  +#endif
>  +
>   TIMEINFO*
>   PcGetTime(VOID)
>   {
>       static TIMEINFO TimeInfo;
>  +
>  +#ifndef INT386_WITH_INT_1A_AH_02_04__IS__FIXED
>  +
>  +    /* Loop while update is in progress */
>  +    while ((HalpReadCmos(RTC_REGISTER_A)) & RTC_REG_A_UIP);
>  +
>  +    /* Set the time data */
>  +    TimeInfo.Second = BCD_INT(HalpReadCmos(0));
>  +    TimeInfo.Minute = BCD_INT(HalpReadCmos(2));
>  +    TimeInfo.Hour = BCD_INT(HalpReadCmos(4));
>  +    TimeInfo.Day = BCD_INT(HalpReadCmos(7));
>  +    TimeInfo.Month = BCD_INT(HalpReadCmos(8));
>  +    TimeInfo.Year = BCD_INT(HalpReadCmos(9));
>  +
>  +    /* Compensate for the century field */
>  +    TimeInfo.Year += (TimeInfo.Year > 80) ? 1900: 2000;
>  +
>  +#else
>  +
>       REGS Regs;
>   
>       for (;;)
>  @@ -86,6 +126,9 @@
>   
>           break;
>       }
>  +
>  +#endif
>  +
>       return &TimeInfo;
>   }
>   
>  
>   

-- 
Pierre Schweitzer <pierre at reactos.org>
System & Network Administrator
Senior Kernel Developer
ReactOS Deutschland e.V.