1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
|
/* SPDX-License-Identifier: GPL-2.0 */
#include <asm/asm-offsets.h>
#include <asm/asm.h>
#include <asm/frame.h>
#include <asm/unwind_hints.h>
#include <linux/linkage.h>
#include <linux/bits.h>
#include <linux/errno.h>
#include "../../virt/vmx/tdx/tdxcall.S"
/*
* Bitmasks of exposed registers (with VMM).
*/
#define TDX_R10 BIT(10)
#define TDX_R11 BIT(11)
#define TDX_R12 BIT(12)
#define TDX_R13 BIT(13)
#define TDX_R14 BIT(14)
#define TDX_R15 BIT(15)
/*
* These registers are clobbered to hold arguments for each
* TDVMCALL. They are safe to expose to the VMM.
* Each bit in this mask represents a register ID. Bit field
* details can be found in TDX GHCI specification, section
* titled "TDCALL [TDG.VP.VMCALL] leaf".
*/
#define TDVMCALL_EXPOSE_REGS_MASK ( TDX_R10 | TDX_R11 | \
TDX_R12 | TDX_R13 | \
TDX_R14 | TDX_R15 )
.section .noinstr.text, "ax"
/*
* __tdx_module_call() - Used by TDX guests to request services from
* the TDX module (does not include VMM services) using TDCALL instruction.
*
* Transforms function call register arguments into the TDCALL register ABI.
* After TDCALL operation, TDX module output is saved in @out (if it is
* provided by the user).
*
*-------------------------------------------------------------------------
* TDCALL ABI:
*-------------------------------------------------------------------------
* Input Registers:
*
* RAX - TDCALL Leaf number.
* RCX,RDX,R8-R9 - TDCALL Leaf specific input registers.
*
* Output Registers:
*
* RAX - TDCALL instruction error code.
* RCX,RDX,R8-R11 - TDCALL Leaf specific output registers.
*
*-------------------------------------------------------------------------
*
* __tdx_module_call() function ABI:
*
* @fn (RDI) - TDCALL Leaf ID, moved to RAX
* @rcx (RSI) - Input parameter 1, moved to RCX
* @rdx (RDX) - Input parameter 2, moved to RDX
* @r8 (RCX) - Input parameter 3, moved to R8
* @r9 (R8) - Input parameter 4, moved to R9
*
* @out (R9) - struct tdx_module_output pointer
* stored temporarily in R12 (not
* shared with the TDX module). It
* can be NULL.
*
* Return status of TDCALL via RAX.
*/
SYM_FUNC_START(__tdx_module_call)
FRAME_BEGIN
TDX_MODULE_CALL host=0
FRAME_END
RET
SYM_FUNC_END(__tdx_module_call)
/*
* __tdx_hypercall() - Make hypercalls to a TDX VMM using TDVMCALL leaf
* of TDCALL instruction
*
* Transforms values in function call argument struct tdx_hypercall_args @args
* into the TDCALL register ABI. After TDCALL operation, VMM output is saved
* back in @args.
*
*-------------------------------------------------------------------------
* TD VMCALL ABI:
*-------------------------------------------------------------------------
*
* Input Registers:
*
* RAX - TDCALL instruction leaf number (0 - TDG.VP.VMCALL)
* RCX - BITMAP which controls which part of TD Guest GPR
* is passed as-is to the VMM and back.
* R10 - Set 0 to indicate TDCALL follows standard TDX ABI
* specification. Non zero value indicates vendor
* specific ABI.
* R11 - VMCALL sub function number
* RBX, RBP, RDI, RSI - Used to pass VMCALL sub function specific arguments.
* R8-R9, R12-R15 - Same as above.
*
* Output Registers:
*
* RAX - TDCALL instruction status (Not related to hypercall
* output).
* R10 - Hypercall output error code.
* R11-R15 - Hypercall sub function specific output values.
*
*-------------------------------------------------------------------------
*
* __tdx_hypercall() function ABI:
*
* @args (RDI) - struct tdx_hypercall_args for input and output
* @flags (RSI) - TDX_HCALL_* flags
*
* On successful completion, return the hypercall error code.
*/
SYM_FUNC_START(__tdx_hypercall)
FRAME_BEGIN
/* Save callee-saved GPRs as mandated by the x86_64 ABI */
push %r15
push %r14
push %r13
push %r12
/* Mangle function call ABI into TDCALL ABI: */
/* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */
xor %eax, %eax
/* Copy hypercall registers from arg struct: */
movq TDX_HYPERCALL_r10(%rdi), %r10
movq TDX_HYPERCALL_r11(%rdi), %r11
movq TDX_HYPERCALL_r12(%rdi), %r12
movq TDX_HYPERCALL_r13(%rdi), %r13
movq TDX_HYPERCALL_r14(%rdi), %r14
movq TDX_HYPERCALL_r15(%rdi), %r15
movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx
tdcall
/*
* RAX==0 indicates a failure of the TDVMCALL mechanism itself and that
* something has gone horribly wrong with the TDX module.
*
* The return status of the hypercall operation is in a separate
* register (in R10). Hypercall errors are a part of normal operation
* and are handled by callers.
*/
testq %rax, %rax
jne .Lpanic
/* TDVMCALL leaf return code is in R10 */
movq %r10, %rax
/* Copy hypercall result registers to arg struct if needed */
testq $TDX_HCALL_HAS_OUTPUT, %rsi
jz .Lout
movq %r10, TDX_HYPERCALL_r10(%rdi)
movq %r11, TDX_HYPERCALL_r11(%rdi)
movq %r12, TDX_HYPERCALL_r12(%rdi)
movq %r13, TDX_HYPERCALL_r13(%rdi)
movq %r14, TDX_HYPERCALL_r14(%rdi)
movq %r15, TDX_HYPERCALL_r15(%rdi)
.Lout:
/*
* Zero out registers exposed to the VMM to avoid speculative execution
* with VMM-controlled values. This needs to include all registers
* present in TDVMCALL_EXPOSE_REGS_MASK (except R12-R15). R12-R15
* context will be restored.
*/
xor %r10d, %r10d
xor %r11d, %r11d
/* Restore callee-saved GPRs as mandated by the x86_64 ABI */
pop %r12
pop %r13
pop %r14
pop %r15
FRAME_END
RET
.Lpanic:
call __tdx_hypercall_failed
/* __tdx_hypercall_failed never returns */
REACHABLE
jmp .Lpanic
SYM_FUNC_END(__tdx_hypercall)
|
