Re: [ros-dev] [ros-diffs] [ion] 52807: [KERNEL32]: Optimize SwitchToFiber to simply use "ret" to jump between fibers, instead of saving EIP and doing a JMP. Bug #50: SwitchToFiber needs to check if FXSR is *NOT* present in ...

[Timo Kreuzer]

This won't work, since new Fibers, created with CreateFiber(Ex) don't 
push a "return address" on the stack, but set the Eip member to 
BaseFiberStartup.


Am 23.07.2011 14:08, schrieb ion(a)svn.reactos.org:
>   Author: ion
>  Date: Sat Jul 23 12:08:36 2011
>  New Revision: 52807
>
>  URL: http://svn.reactos.org/svn/reactos?rev=52807&view=rev
>  Log:
>  [KERNEL32]: Optimize SwitchToFiber to simply use "ret" to jump between fibers,
> instead of saving EIP and doing a JMP.
>  Bug #50: SwitchToFiber needs to check if FXSR is *NOT* present in order to skip using
> ldmxcsr/stmxcsr. Previously, it would check if it's unsupported, and jump past the
> instruction if it was (resulting in invalid opcode instructions on older systems)
>  50 bugs. Penance has been paid.
>
>  Modified:
>       trunk/reactos/dll/win32/kernel32/client/i386/fiber.S
>
>  Modified: trunk/reactos/dll/win32/kernel32/client/i386/fiber.S
>  URL:
> http://svn.reactos.org/svn/reactos/trunk/reactos/dll/win32/kernel32/client/…
>  ==============================================================================
>  --- trunk/reactos/dll/win32/kernel32/client/i386/fiber.S [iso-8859-1] (original)
>  +++ trunk/reactos/dll/win32/kernel32/client/i386/fiber.S [iso-8859-1] Sat Jul 23 12:08:36
> 2011
>  @@ -26,20 +26,16 @@
>        mov [eax+FIBER_CONTEXT_EDI], edi
>        mov [eax+FIBER_CONTEXT_EBP], ebp
>
>  -    /* Save the return address */
>  -    mov ebx, [esp]
>  -    mov [eax+FIBER_CONTEXT_EIP], ebx
>  -
>        /* Check if we're to save FPU State */
>        cmp dword ptr [eax+FIBER_CONTEXT_FLAGS], CONTEXT_FULL OR CONTEXT_FLOATING_POINT
>        jnz NoFpuStateSave
>
>        /* Save the FPU State (Status and Control)*/
>        fstsw [eax+FIBER_CONTEXT_FLOAT_SAVE_STATUS_WORD]
>  -    fstcw [eax+FIBER_CONTEXT_FLOAT_SAVE_CONTROL_WORD]
>  +    fnstcw [eax+FIBER_CONTEXT_FLOAT_SAVE_CONTROL_WORD]
>
>        /* Check if the CPU supports SIMD MXCSR State Save */
>  -    cmp byte ptr ds:[PROCESSOR_FEATURE_FXSR], 0
>  +    cmp byte ptr ds:[PROCESSOR_FEATURE_FXSR], 1
>        jnz NoFpuStateSave
>        stmxcsr [eax+FIBER_CONTEXT_DR6]
>
>  @@ -103,7 +99,7 @@
>    ControlWordEqual:
>
>        /* Load the new one */
>  -    cmp byte ptr ds:[PROCESSOR_FEATURE_FXSR], 0
>  +    cmp byte ptr ds:[PROCESSOR_FEATURE_FXSR], 1
>        jnz NoFpuStateRestore
>        ldmxcsr [ecx+FIBER_CONTEXT_DR6]
>
>  @@ -121,7 +117,8 @@
>        mov [edx+TEB_FLS_DATA], eax
>
>        /* Jump to new fiber */
>  -    jmp dword ptr [ecx+FIBER_CONTEXT_EIP]
>  +    mov esp, [ecx+FIBER_CONTEXT_ESP]
>  +    ret 4
>  +END
>
>  -END
>    /* EOF */
>
>
>