On Sun, Jul 31, 2022, Michal Luczaj wrote:
> Check if the emulator throws #UD on illegal LEA.
Please explicitly state exactly what illegal LEA is being generated. Requiring
readers to connect the dots of the LEA opcode and ModR/M encoding is unnecessarily
mean :-)
> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Michal Luczaj <mhal@xxxxxxx>
> ---
> v1 -> v2: Instead of racing decoder make use of force_emulation_prefix
>
> x86/emulator.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/x86/emulator.c b/x86/emulator.c
> index cd78e3c..c3898f2 100644
> --- a/x86/emulator.c
> +++ b/x86/emulator.c
> @@ -895,6 +895,24 @@ static void test_mov_dr(uint64_t *mem)
> report(rax == DR6_ACTIVE_LOW, "mov_dr6");
> }
>
> +static void illegal_lea_handler(struct ex_regs *regs)
> +{
> + extern char illegal_lea_cont;
> +
> + ++exceptions;
> + regs->rip = (ulong)&illegal_lea_cont;
> +}
> +
> +static void test_illegal_lea(uint64_t *mem)
@mem isn't needed.
> +{
> + exceptions = 0;
> + handle_exception(UD_VECTOR, illegal_lea_handler);
No need to use a custom handler (ignore any patterns in emulator.c that suggest
it's "mandatory", emulator is one of the oldest test). ASM_TRY() can handle all
of this without any globals.
> + asm(KVM_FEP ".byte 0x48; .byte 0x8d; .byte 0xc0\n\t"
> + "illegal_lea_cont:" : : : "rax");
"emulator" is compatible with 32-bit KUT, drop the REX prefix and clobber "eax"
instead of "xax".
> + report(exceptions == 1, "illegal lea");
Be nice to future debuggers. Call out what is illegal about LEA, capitalize LEA
to make it more obvious that its an instruction, and print the expected versus
actual.
> + handle_exception(UD_VECTOR, 0);
> +}
So this?
static void test_illegal_lea(void)
{
unsigned int vector;
asm volatile (ASM_TRY("1f")
KVM_FEP ".byte 0x8d; .byte 0xc0\n\t"
"1:"
: : : "memory", "eax");
vector = exception_vector();
report(vector == UD_VECTOR,
"Wanted #UD on LEA with /reg, got vector = %d", vector);
}
> +
> static void test_push16(uint64_t *mem)
> {
> uint64_t rsp1, rsp2;
> @@ -1193,6 +1211,7 @@ int main(void)
> test_smsw_reg(mem);
> test_nop(mem);
> test_mov_dr(mem);
> + test_illegal_lea(mem);
> } else {
> report_skip("skipping register-only tests, "
> "use kvm.force_emulation_prefix=1 to enable");
> --
> 2.32.0
>
