Attachment 879241 Details for Bug 1081262 – fix thats applied in Debian

[patch] fix thats applied in Debian

vgabios-attempt-to-detect-old-x86emu-and-force-a-fault.diff (text/plain), 2.40 KB, created by Matthias Clasen on 2014-03-26 22:21:54 UTC

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Creator: Matthias Clasen

Created: 2014-03-26 22:21:54 UTC

Size: 2.40 KB

patch

obsolete

>From: Kevin O'Connor <kevin@koconnor.net>
>Date: Wed Feb 5 22:47:29 2014 -0500
>Subject: vgabios: Attempt to detect old x86emu and force a fault.
>Upstream-Commit: 8032b8a0fec550de5cb2f7d37aa031cebc2200c3
>Bug-Debian: http://bugs.debian.org/737142
>
>Check for cases where the leal instruction does not work.  This
>instruction is known to not be emulated properly on old versions of
>x86emu.  If a broken version of x86emu is found, force a fault that
>x86emu will easily detect.  This should help prevent soft failures
>when running old software.
>    
>Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
>
>diff --git a/vgasrc/vgaentry.S b/vgasrc/vgaentry.S
>index 9854448..6e31c4e 100644
>--- a/vgasrc/vgaentry.S
>+++ b/vgasrc/vgaentry.S
>@@ -45,9 +45,26 @@ _rom_header_signature:
>  * Entry points
>  ****************************************************************/
> 
>-        // This macro is the same as ENTRY_ARG except the "calll"
>-        // instruction is avoided to work around known issues in the
>-        // emulation of some versions of x86emu.
>+        // Force a fault if found to be running on broken x86emu versions.
>+        DECLFUNC x86emu_fault
>+x86emu_fault:
>+1:      hlt
>+        jmp 1b
>+
>+        // This macro implements a call while avoiding instructions
>+        // that old versions of x86emu have problems with.
>+        .macro VGA_CALLL cfunc
>+        // Make sure leal instruction works.
>+        movl $0x8000, %ecx
>+        leal (%ecx, %ecx, 1), %ecx
>+        cmpl $0x10000, %ecx
>+        jne x86emu_fault
>+        // Use callw instead of calll
>+        push %ax
>+        callw \cfunc
>+        .endm
>+
>+        // This macro is the same as ENTRY_ARG except VGA_CALLL is used.
>         .macro ENTRY_ARG_VGA cfunc
>         cli
>         cld
>@@ -57,7 +74,7 @@ _rom_header_signature:
>         movl %esp, %ebx         // Backup %esp, then zero high bits
>         movzwl %sp, %esp
>         movl %esp, %eax         // First arg is pointer to struct bregs
>-        pushw %ax ; callw \cfunc
>+        VGA_CALLL \cfunc
>         movl %ebx, %esp         // Restore %esp (including high bits)
>         POPBREGS
>         .endm
>@@ -103,7 +120,7 @@ entry_10_extrastack:
>         movw %ds, %dx           // Setup %ss/%esp and call function
>         movw %dx, %ss
>         movl %eax, %esp
>-        pushw %ax ; callw handle_10
>+        VGA_CALLL handle_10
> 
>         movl %esp, %eax         // Restore registers and return
>         movw BREGS_size+4(%eax), %ss

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