diff options
Diffstat (limited to 'arch/x86/xen/xen-asm.S')
| -rw-r--r-- | arch/x86/xen/xen-asm.S | 42 |
1 files changed, 28 insertions, 14 deletions
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S index fe161ed4b01..2497a30f41d 100644 --- a/arch/x86/xen/xen-asm.S +++ b/arch/x86/xen/xen-asm.S @@ -108,6 +108,20 @@ ENDPATCH(xen_restore_fl_direct) RELOC(xen_restore_fl_direct, 2b+1) /* + We can't use sysexit directly, because we're not running in ring0. + But we can easily fake it up using iret. Assuming xen_sysexit + is jumped to with a standard stack frame, we can just strip it + back to a standard iret frame and use iret. + */ +ENTRY(xen_sysexit) + movl PT_EAX(%esp), %eax /* Shouldn't be necessary? */ + orl $X86_EFLAGS_IF, PT_EFLAGS(%esp) + lea PT_EIP(%esp), %esp + + jmp xen_iret +ENDPROC(xen_sysexit) + +/* This is run where a normal iret would be run, with the same stack setup: 8: eflags 4: cs @@ -184,8 +198,12 @@ iret_restore_end: region is OK. */ je xen_hypervisor_callback - iret +1: iret xen_iret_end_crit: +.section __ex_table,"a" + .align 4 + .long 1b,iret_exc +.previous hyper_iret: /* put this out of line since its very rarely used */ @@ -219,9 +237,7 @@ hyper_iret: ds } SAVE_ALL state eax } : : - ebx } - ---------------- - return addr <- esp + ebx }<- esp ---------------- In order to deliver the nested exception properly, we need to shift @@ -236,10 +252,8 @@ hyper_iret: it's usermode state which we eventually need to restore. */ ENTRY(xen_iret_crit_fixup) - /* offsets +4 for return address */ - /* - Paranoia: Make sure we're really coming from userspace. + Paranoia: Make sure we're really coming from kernel space. One could imagine a case where userspace jumps into the critical range address, but just before the CPU delivers a GP, it decides to deliver an interrupt instead. Unlikely? @@ -248,32 +262,32 @@ ENTRY(xen_iret_crit_fixup) jump instruction itself, not the destination, but some virtual environments get this wrong. */ - movl PT_CS+4(%esp), %ecx + movl PT_CS(%esp), %ecx andl $SEGMENT_RPL_MASK, %ecx cmpl $USER_RPL, %ecx je 2f - lea PT_ORIG_EAX+4(%esp), %esi - lea PT_EFLAGS+4(%esp), %edi + lea PT_ORIG_EAX(%esp), %esi + lea PT_EFLAGS(%esp), %edi /* If eip is before iret_restore_end then stack hasn't been restored yet. */ cmp $iret_restore_end, %eax jae 1f - movl 0+4(%edi),%eax /* copy EAX */ - movl %eax, PT_EAX+4(%esp) + movl 0+4(%edi),%eax /* copy EAX (just above top of frame) */ + movl %eax, PT_EAX(%esp) lea ESP_OFFSET(%edi),%edi /* move dest up over saved regs */ /* set up the copy */ 1: std - mov $(PT_EIP+4) / 4, %ecx /* copy ret+saved regs up to orig_eax */ + mov $PT_EIP / 4, %ecx /* saved regs up to orig_eax */ rep movsl cld lea 4(%edi),%esp /* point esp to new frame */ -2: ret +2: jmp xen_do_upcall /* |