On Wed, Jun 19, 2013 at 11:00:56PM +0800, Arthur Chunqi Li wrote:
> 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 | 110
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 110 insertions(+)
> mode change 100644 => 100755 x86/emulator.c
>
> diff --git a/x86/emulator.c b/x86/emulator.c
> old mode 100644
> new mode 100755
> index 96576e5..48d45c8
> --- a/x86/emulator.c
> +++ b/x86/emulator.c
> @@ -11,6 +11,15 @@ int fails, tests;
>
> static int exceptions;
>
> +struct regs {
> + u64 rax, rbx, rcx, rdx;
> + u64 rsi, rdi, rsp, rbp;
> + u64 r8, r9, r10, r11;
> + u64 r12, r13, r14, r15;
> + u64 rip, rflags;
> +};
> +struct regs inregs, outregs, save;
> +
> void report(const char *name, int result)
> {
> ++tests;
> @@ -685,6 +694,107 @@ static void test_shld_shrd(u32 *mem)
> report("shrd (cl)", *mem == ((0x12345678 >> 3) | (5u << 29)));
> }
>
> +#define INSN_SAVE \
No need for all the defines. Put all the code into insn_page, allocate
alt_insn_page dynamically and copy the code there by memcpy.
> + "ret\n\t" \
> + "pushf\n\t" \
> + "push 136+save \n\t" \
> + "popf \n\t" \
> + "xchg %rax, 0+save \n\t" \
> + "xchg %rbx, 8+save \n\t" \
> + "xchg %rcx, 16+save \n\t" \
> + "xchg %rdx, 24+save \n\t" \
> + "xchg %rsi, 32+save \n\t" \
> + "xchg %rdi, 40+save \n\t" \
> + "xchg %rsp, 48+save \n\t" \
> + "xchg %rbp, 56+save \n\t" \
> + "xchg %r8, 64+save \n\t" \
> + "xchg %r9, 72+save \n\t" \
> + "xchg %r10, 80+save \n\t" \
> + "xchg %r11, 88+save \n\t" \
> + "xchg %r12, 96+save \n\t" \
> + "xchg %r13, 104+save \n\t" \
> + "xchg %r14, 112+save \n\t" \
> + "xchg %r15, 120+save \n\t" \
> +
> +#define INSN_RESTORE \
> + "xchg %rax, 0+save \n\t" \
> + "xchg %rbx, 8+save \n\t" \
> + "xchg %rcx, 16+save \n\t" \
> + "xchg %rdx, 24+save \n\t" \
> + "xchg %rsi, 32+save \n\t" \
> + "xchg %rdi, 40+save \n\t" \
> + "xchg %rsp, 48+save \n\t" \
> + "xchg %rbp, 56+save \n\t" \
> + "xchg %r8, 64+save \n\t" \
> + "xchg %r9, 72+save \n\t" \
> + "xchg %r10, 80+save \n\t" \
> + "xchg %r11, 88+save \n\t" \
> + "xchg %r12, 96+save \n\t" \
> + "xchg %r13, 104+save \n\t" \
> + "xchg %r14, 112+save \n\t" \
> + "xchg %r15, 120+save \n\t" \
> + "pushf \n\t" \
> + "pop 136+save \n\t" \
> + "popf \n\t" \
> + "ret \n\t" \
> +
> +#define INSN_TRAP \
> + "in (%dx),%al\n\t" \
> + ". = . + 31\n\t" \
If you will do ".skip 31, 0x90\n\t" instead you can drop loop
that inserts nops bellow.
> +
> +asm(
> + ".align 4096\n\t"
> + "insn_page:\n\t"
> + INSN_SAVE
> + "test_insn:\n\t"
> + INSN_TRAP
> + "test_insn_end:\n\t"
> + INSN_RESTORE
> + "insn_page_end:\n\t"
> + ".align 4096\n\t"
> +
> + "alt_insn_page:\n\t"
> + INSN_SAVE
> + "alt_test_insn:\n\t"
> + INSN_TRAP
> + "alt_test_insn_end:\n\t"
> + INSN_RESTORE
> + "alt_insn_page_end:\n\t"
> + ".align 4096\n\t"
> +);
> +
> +static void trap_emulator(uint64_t *mem, uint8_t* alt_insn, int
> alt_insn_length)
> +{
> + ulong *cr3 = (ulong *)read_cr3();
> + void *insn_ram;
> + int i;
> + extern u8 insn_page[], test_insn[], test_insn_end[];
> + extern u8 alt_insn_page[], alt_test_insn[];
> +
> + insn_ram = vmap(virt_to_phys(insn_page), 4096);
> + for (i=1; i<test_insn_end - test_insn; i++)
> + alt_test_insn[i] = test_insn[i] = 0x90; // nop
> + for (i=0; i<alt_insn_length; i++)
> + alt_test_insn[i] = alt_insn[i];
> + for(;i<test_insn_end - test_insn; i++)
> + alt_test_insn[i] = 0x90; // nop
> + save = inregs;
> +
> + // 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.
I prefer all the comments to be changed to /**/ style while we are at it.
> + install_page(cr3, virt_to_phys(insn_page), insn_ram);
> + invlpg(insn_ram);
> + // Load code TLB
> + asm volatile("call *%0" : : "r"(insn_ram));
> + install_page(cr3, virt_to_phys(alt_insn_page), insn_ram);
> + // Trap, let hypervisor emulate at alt_insn_page
> + asm volatile("call *%0": : "r"(insn_ram+1));
> +
> + outregs = save;
> +}
> +
> static void advance_rip_by_3_and_note_exception(struct ex_regs *regs)
> {
> ++exceptions;
> --
> 1.7.9.5
--
Gleb.
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