Add a function trap_emulator to run an instruction in emulator. Set inregs first (%rax is invalid because it is used as return address), put instruction codec in alt_insn and call func with alt_insn_length. Get results in outregs.
Signed-off-by: Arthur Chunqi Li <[email protected]> --- x86/emulator.c | 81 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 81 insertions(+) diff --git a/x86/emulator.c b/x86/emulator.c index 96576e5..8ab9904 100644 --- a/x86/emulator.c +++ b/x86/emulator.c @@ -11,6 +11,14 @@ int fails, tests; static int exceptions; +struct regs { + u64 rax, rbx, rcx, rdx; + u64 rsi, rdi, rsp, rbp; + u64 rip, rflags; +}; + +static struct regs inregs, outregs; + void report(const char *name, int result) { ++tests; @@ -685,6 +693,79 @@ static void test_shld_shrd(u32 *mem) report("shrd (cl)", *mem == ((0x12345678 >> 3) | (5u << 29))); } +static void trap_emulator(uint64_t *mem, uint8_t *insn_page, + uint8_t *alt_insn_page, void *insn_ram, + uint8_t *alt_insn, int alt_insn_length) +{ + ulong *cr3 = (ulong *)read_cr3(); + int i; + + // Pad with RET instructions + memset(insn_page, 0xc3, 4096); + memset(alt_insn_page, 0xc3, 4096); + + // Place a trapping instruction in the page to trigger a VMEXIT + insn_page[0] = 0x89; // mov %eax, (%rax) + insn_page[1] = 0x00; + insn_page[2] = 0x90; // nop + insn_page[3] = 0xc3; // ret + + // Place the instruction we want the hypervisor to see in the alternate page + for (i=0; i<alt_insn_length; i++) + alt_insn_page[i] = alt_insn[i]; + + // Save general registers + asm volatile( + "push %rax\n\r" + "push %rbx\n\r" + "push %rcx\n\r" + "push %rdx\n\r" + "push %rsi\n\r" + "push %rdi\n\r" + ); + // Load the code TLB with insn_page, but point the page tables at + // alt_insn_page (and keep the data TLB clear, for AMD decode assist). + // This will make the CPU trap on the insn_page instruction but the + // hypervisor will see alt_insn_page. + install_page(cr3, virt_to_phys(insn_page), insn_ram); + invlpg(insn_ram); + // Load code TLB + asm volatile("call *%0" : : "r"(insn_ram + 3)); + install_page(cr3, virt_to_phys(alt_insn_page), insn_ram); + // Trap, let hypervisor emulate at alt_insn_page + asm volatile( + "call *%1\n\r" + + "mov %%rax, 0+%[outregs] \n\t" + "mov %%rbx, 8+%[outregs] \n\t" + "mov %%rcx, 16+%[outregs] \n\t" + "mov %%rdx, 24+%[outregs] \n\t" + "mov %%rsi, 32+%[outregs] \n\t" + "mov %%rdi, 40+%[outregs] \n\t" + "mov %%rsp,48+ %[outregs] \n\t" + "mov %%rbp, 56+%[outregs] \n\t" + + /* Save RFLAGS in outregs*/ + "pushf \n\t" + "popq 72+%[outregs] \n\t" + : [outregs]"+m"(outregs) + : "r"(insn_ram), + "a"(mem), "b"(inregs.rbx), + "c"(inregs.rcx), "d"(inregs.rdx), + "S"(inregs.rsi), "D"(inregs.rdi) + : "memory", "cc" + ); + // Restore general registers + asm volatile( + "pop %rax\n\r" + "pop %rbx\n\r" + "pop %rcx\n\r" + "pop %rdx\n\r" + "pop %rsi\n\r" + "pop %rdi\n\r" + ); +} + static void advance_rip_by_3_and_note_exception(struct ex_regs *regs) { ++exceptions; -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
