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