On Wed, 2017-01-25 at 12:38 -0800, H. Peter Anvin wrote:
On 01/25/17 12:23, Ricardo Neri wrote:
+ case UMIP_SMSW: + dummy_value = CR0_STATE;
Unless the user space process is running in 64-bit mode this value should be & 0xffff.
But wouldn't that prevent the bits CR0[63:16] or CR0[31:16] from being copied when a register operand is used? According to the Intel Software Development manual, SMSW returns SMSW r16 operand size 16, store CR0[15:0] in r16 SMSW r32 operand size 32, zero-extend CR0[31:0], and store in r32 SMSW r64 operand size 64, zero-extend CR0[63:0], and store in r64 The number of bytes returned by the emulated results is controlled by the data_size variable. If it finds that the result will be saved in a memory location, it will only copy CR0[15:0], which is the expected behavior of SMSW if the result is to be copied in memory.
I'm not sure if we should even support fixing up UMIP instructions in 64-bit mode.
Probably not. The whole point of the emulation was to support virtual-8086 mode and 32-bit mode.
Also, please put an explicit /* fall through */ here.
Will do.
+ /* + * These two instructions return a 16-bit value. We return + * all zeros. This is equivalent to a null descriptor for + * str and sldt. + */ + case UMIP_SLDT: + case UMIP_STR: + /* if operand is a register, it is zero-extended*/ + if (X86_MODRM_MOD(insn->modrm.value) == 3) { + memset(data, 0, insn->opnd_bytes); + *data_size = insn->opnd_bytes; + /* if not, only the two least significant bytes are copied */ + } else { + *data_size = 2; + } + memcpy(data, &dummy_value, sizeof(dummy_value)); + break;
The code above controls how many bytes are copied as the result of SMSW.
+ default: + return -EINVAL; + } + return 0;
+bool fixup_umip_exception(struct pt_regs *regs) +{ + struct insn insn; + unsigned char buf[MAX_INSN_SIZE]; + /* 10 bytes is the maximum size of the result of UMIP instructions */ + unsigned char dummy_data[10] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; +#ifdef CONFIG_X86_64 + int x86_64 = user_64bit_mode(regs); +#else + int x86_64 = 0; +#endif
Again, could we simply do:
if (user_64bit_mode(regs)) return false;
or are there known users of these instructions *in 64-bit mode*?
I am not aware of any. In that case, I will make this code return in this case. Thanks and BR, Ricardo
-hpa