Re: [PATCH 1/2] kvm-unit-tests: Add a func to run instruction in emulator

[Gleb Natapov <gleb@redhat.com>]

On Thu, Jun 20, 2013 at 06:45:21PM +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.
> 
Looks good, some comment bellow.

> Signed-off-by: Arthur Chunqi Li <yzt356@gmail.com>
> ---
>  lib/libcflat.h |    1 +
>  lib/string.c   |   12 +++++++++
>  x86/emulator.c |   78 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 91 insertions(+)
> 
> diff --git a/lib/libcflat.h b/lib/libcflat.h
> index 0875bd9..fadc33d 100644
> --- a/lib/libcflat.h
> +++ b/lib/libcflat.h
> @@ -50,6 +50,7 @@ extern int vsnprintf(char *buf, int size, const char *fmt, va_list va);
>  extern void puts(const char *s);
>  
>  extern void *memset(void *s, int c, size_t n);
> +extern void *memcpy(void *dest, const void *src, size_t n);
>  
>  extern long atol(const char *ptr);
>  #define ARRAY_SIZE(_a)  (sizeof(_a)/sizeof((_a)[0]))
> diff --git a/lib/string.c b/lib/string.c
> index 9dc94a1..e798f86 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -42,6 +42,18 @@ void *memset(void *s, int c, size_t n)
>      return s;
>  }
>  
> +void *memcpy(void *dest, const void *src, size_t n)
> +{
> +    size_t i;
> +    char *a = dest;
> +    char *b = src;
> +
> +    for (i = 0; i < n; ++i)
> +        a[i] = b[i];
> +
> +    return dest;
> +}
> +
memcpy addition should be in separate patch usually, but for unit test
it is no a big deal.

>  long atol(const char *ptr)
>  {
>      long acc = 0;
> diff --git a/x86/emulator.c b/x86/emulator.c
> index 96576e5..b3626fa 100644
> --- 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 +694,75 @@ static void test_shld_shrd(u32 *mem)
>      report("shrd (cl)", *mem == ((0x12345678 >> 3) | (5u << 29)));
>  }
>  
> +#define INSN_XCHG_ALL			\
> +	"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"		\
> +
> +asm(
> +	".align 4096\n\t"
> +	"insn_page:\n\t"
> +	"ret\n\t"
> +	"pushf\n\t"
> +	"push 136+save \n\t"
> +	"popf \n\t"
> +	INSN_XCHG_ALL
> +	"test_insn:\n\t"
> +	"in  (%dx),%al\n\t"
> +	".skip 31, 0x90\n\t"
> +	"test_insn_end:\n\t"
> +	INSN_XCHG_ALL
> +	"pushf \n\t"
> +	"pop 136+save \n\t"
> +	"popf \n\t"
> +	"ret \n\t"
> +	"insn_page_end:\n\t"
> +	".align 4096\n\t"
> +
> +	"alt_insn_page:\n\t"
> +	". = . + 4096\n\t"
> +	".align 4096\n\t"
alt_insn_page can be allocated by alloc_page().

> +);
> +
> +static void trap_emulator(uint64_t *mem, uint8_t* alt_insn, int alt_insn_length)
> +{
> +	ulong *cr3 = (ulong *)read_cr3();
> +	void *insn_ram;
> +	extern u8 insn_page[], test_insn[], alt_insn_page[];
> +
> +	insn_ram = vmap(virt_to_phys(insn_page), 4096);
> +	memcpy(alt_insn_page, test_insn, 4096);
> +	memcpy(alt_insn_page + (test_insn - insn_page), alt_insn, alt_insn_length);
> +	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. */
> +	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.