Yang, Sheng wrote: > From 9743b5299bae1779c2b893cbeb86122bcccb9b2d Mon Sep 17 00:00:00 2001 > From: Sheng Yang <[EMAIL PROTECTED]> > Date: Wed, 2 Jan 2008 14:49:22 +0800 > Subject: [PATCH] KVM: emulator: Only allow VMCALL/VMMCALL trapped by #UD > > When executing a test program called "crashme", we found the KVM guest cannot > survived more than ten seconds, then encounterd kernel panic. The basic > concept of "crashme" is graduating random assembly code and trying to execute > them in a fork process. > > After some fix on emulator valid judgment, we found it's hard to get the > current emulator handle the invalid instructions correctly, for the #UD trap > for hypercall patching caused troubles. The problem is, if the opcode itself > was OK, but combination of opcode and modrm_reg was invalid, and one operand > of the opcode was memory(SrcMem or DstMem), emulator would fetched the memory > operand first rather than judged the validity, and may encounter error there. > For example, ".byte 0xfe, 0x34, 0xcd" got this trouble. > > In the patch, we simply check that if the invalid opcode isn't > vmcall/vmmcall, > then return from emulate_instruction() and inject a #UD to guest. With the > patch, the guest had been run for more than 12 hours. > >
Applied, thanks. As Anthony says, good catch indeed. I have a vague plan for improving decode; basically extend the decode tables to add group decoding. We add a bit to opcode_table and twobyte_table that is set for all instructions which need group decoding. When the bit is set, the rest of the value in opcode_table is interpreted as an index (together with modrm_reg) into a new group_table, so we can have different decoding for such instructions. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
