On Wed, Nov 13, 2002 at 09:48:15PM +0000, Alan Cox wrote:
> On Wed, 2002-11-13 at 21:18, Petr Vandrovec wrote:
> > > pushfl # We get a different stack layout with call
> > > # gates, which has to be cleaned up later..
> > > + andl $~0x4500, (%esp) # Clear NT since we are doing an iret
> >
> > this will clear 'D' and 'T' in caller after we do
> > iret (if lcall7 returns, of course). I'm not sure that callers
>
> You can adjust that if you want, I copied it about - clearing D is fine,
> in fact it may let us avoid the cld
Hi,
your original code just behaved as my old code: run modprobe successfully,
and then die. Problem is that copy of eflags on stack is totally unimportant
to us: current value in eflags is what matters. So this is minimal
patch which works here: NT, DF and TF are now cleared only for kernel,
and when we return back from lcall, userspace has its old values.
Optimization left to readed is creating SAVE_ALL_NOCLD, and using this
one in lcall7 and lcall27.
With patch below my machine survived test. Unfortunately I do not
have patched kernel with linux-abi to test whether lcall7 still works
correctly.
Best regards,
Petr Vandrovec
vandrove@vc.cvut.cz
--- linux-2.5.47.dist/arch/i386/kernel/entry.S 2002-11-11 12:26:04.000000000 +0100
+++ linux-2.5.47/arch/i386/kernel/entry.S 2002-11-13 22:40:19.000000000 +0100
@@ -66,7 +66,9 @@
OLDSS = 0x38
CF_MASK = 0x00000001
+TF_MASK = 0x00000100
IF_MASK = 0x00000200
+DF_MASK = 0x00000400
NT_MASK = 0x00004000
VM_MASK = 0x00020000
@@ -132,6 +134,9 @@
movl CS(%esp), %edx # this is eip..
movl EFLAGS(%esp), %ecx # and this is cs..
movl %eax,EFLAGS(%esp) #
+ andl $~(NT_MASK|TF_MASK|DF_MASK), %eax
+ pushl %eax
+ popfl
movl %edx,EIP(%esp) # Now we move them to their "normal" places
movl %ecx,CS(%esp) #
movl %esp, %ebx
@@ -154,6 +159,9 @@
movl CS(%esp), %edx # this is eip..
movl EFLAGS(%esp), %ecx # and this is cs..
movl %eax,EFLAGS(%esp) #
+ andl $~(NT_MASK|TF_MASK|DF_MASK), %eax
+ pushl %eax
+ popfl
movl %edx,EIP(%esp) # Now we move them to their "normal" places
movl %ecx,CS(%esp) #
movl %esp, %ebx
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Nov 15 2002 - 22:00:30 EST