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Re: [PATCH][2.6-mm] Fix 4G/4G X11/vm86 oops
On Tue, 18 Nov 2003, Linus Torvalds wrote:
> Hmm. I don't see anything. However, it's a lot easier to read the
> gcc-generated assembly ("make arch/i386/kernel/vm86.s") than it is to read
> the objdump disassembly.
>
>
> It's also a lot easier to see what the assembly language is when giving
> the
>
> -fno-reorder-blocks
I'll recompile and verify that the bug can be reproduced and worked around
with that flag.
> switch to gcc. Without it, modern gcc's tend to have _way_ too many jumps
> around. But maybe that actually changes the behaviour too.
Here are diffs from the do_sys_vm86 only.
--- asm-before 2003-11-18 10:56:02.967643808 -0500
+++ asm-after 2003-11-18 10:55:37.880457640 -0500
@@ -897,6 +897,10 @@
.LFE473:
.Lfe4:
.size sys_vm86,.Lfe4-sys_vm86
+ .section .rodata.str1.1
+.LC6:
+ .string "ooh la la\n"
+ .text
.p2align 4,,15
.type do_sys_vm86,@function
do_sys_vm86:
@@ -1053,29 +1057,37 @@
jne .L213
.L210:
.loc 1 315 0
+ pushl $.LC6
+.LCFI98:
+ call printk
+ .loc 1 316 0
movl 4(%esi), %edx
#APP
xorl %eax,%eax; movl %eax,%fs; movl %eax,%gs
movl %edi,%esp
movl %edx,%ebp
jmp resume_userspace
- .loc 1 323 0
#NO_APP
- popl %ebx
-.LCFI98:
+.LBE53:
popl %esi
.LCFI99:
- popl %edi
+ .loc 1 324 0
+ popl %ebx
.LCFI100:
+ popl %esi
+.LCFI101:
+ popl %edi
+.LCFI102:
ret
.loc 1 313 0
.p2align 4,,7
.L213:
+.LBB65:
pushl %esi
-.LCFI101:
+.LCFI103:
call mark_screen_rdonly
popl %eax
-.LCFI102:
+.LCFI104:
jmp .L210
.loc 1 310 0
.L212:
@@ -1083,7 +1095,7 @@
jmp .L197
.loc 14 454 0
.L211:
-.LBB65:
+.LBB66:
movw 36(%edx), %ax
movw %ax, 16(%ecx)
.loc 14 455 0
@@ -1097,7 +1109,7 @@
.p2align 4,,7
.L183:
.loc 1 283 0
-.LBE65:
+.LBE66:
movl $0, 1468(%esi)
.loc 1 284 0
jmp .L182
@@ -1115,7 +1127,7 @@
movl $28672, 1468(%esi)
.loc 1 287 0
jmp .L182
-.LBE53:
+.LBE65:
.LFE475:
.Lfe5:
.size do_sys_vm86,.Lfe5-do_sys_vm86
--
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