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| author | Jan Beulich <jbeulich@suse.com> | 2019-11-11 15:32:59 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-11-19 21:58:28 +0100 |
| commit | 922eea2ce5c799228d9ff1be9890e6873ce8fff6 (patch) | |
| tree | 32e78a83ff9255e5e773bf3e25f04b34d762e655 | |
| parent | 29b810f5a5ec127d3143770098e05981baa3eb77 (diff) | |
| download | linux-922eea2ce5c799228d9ff1be9890e6873ce8fff6.tar.bz2 | |
x86/xen/32: Simplify ring check in xen_iret_crit_fixup()
This can be had with two instead of six insns, by just checking the high
CS.RPL bit.
Also adjust the comment - there would be no #GP in the mentioned cases, as
there's no segment limit violation or alike. Instead there'd be #PF, but
that one reports the target EIP of said branch, not the address of the
branch insn itself.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lkml.kernel.org/r/a5986837-01eb-7bf8-bf42-4d3084d6a1f5@suse.com
| -rw-r--r-- | arch/x86/xen/xen-asm_32.S | 15 |
1 files changed, 4 insertions, 11 deletions
diff --git a/arch/x86/xen/xen-asm_32.S b/arch/x86/xen/xen-asm_32.S index 392e033e40b9..cd177772fe4d 100644 --- a/arch/x86/xen/xen-asm_32.S +++ b/arch/x86/xen/xen-asm_32.S @@ -153,22 +153,15 @@ hyper_iret: * it's still on stack), we need to restore its value here. */ ENTRY(xen_iret_crit_fixup) - pushl %ecx /* * 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? - * Definitely. Easy to avoid? Yes. The Intel documents - * explicitly say that the reported EIP for a bad jump is the - * jump instruction itself, not the destination, but some - * virtual environments get this wrong. + * PF, it decides to deliver an interrupt instead. Unlikely? + * Definitely. Easy to avoid? Yes. */ - movl 3*4(%esp), %ecx /* nested CS */ - andl $SEGMENT_RPL_MASK, %ecx - cmpl $USER_RPL, %ecx - popl %ecx - je 2f + testb $2, 2*4(%esp) /* nested CS */ + jnz 2f /* * If eip is before iret_restore_end then stack |