2 ; Low level x64 routines used by the debug support driver.
4 ; Copyright (c) 2007 - 2018, Intel Corporation. All rights reserved.<BR>
5 ; This program and the accompanying materials
6 ; are licensed and made available under the terms and conditions of the BSD License
7 ; which accompanies this distribution. The full text of the license may be found at
8 ; http://opensource.org/licenses/bsd-license.php
10 ; THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
11 ; WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
15 %define EXCPT64_DIVIDE_ERROR 0
16 %define EXCPT64_DEBUG 1
18 %define EXCPT64_BREAKPOINT 3
19 %define EXCPT64_OVERFLOW 4
20 %define EXCPT64_BOUND 5
21 %define EXCPT64_INVALID_OPCODE 6
22 %define EXCPT64_DOUBLE_FAULT 8
23 %define EXCPT64_INVALID_TSS 10
24 %define EXCPT64_SEG_NOT_PRESENT 11
25 %define EXCPT64_STACK_FAULT 12
26 %define EXCPT64_GP_FAULT 13
27 %define EXCPT64_PAGE_FAULT 14
28 %define EXCPT64_FP_ERROR 16
29 %define EXCPT64_ALIGNMENT_CHECK 17
30 %define EXCPT64_MACHINE_CHECK 18
31 %define EXCPT64_SIMD 19
33 %define FXSTOR_FLAG 0x1000000 ; bit cpuid 24 of feature flags
35 ;; The FXSTOR and FXRSTOR commands are used for saving and restoring the x87,
36 ;; MMX, SSE, SSE2, etc registers. The initialization of the debugsupport driver
37 ;; MUST check the CPUID feature flags to see that these instructions are available
38 ;; and fail to init if they are not.
42 db 0xf, 0xae, 00000111y ; mod = 00, reg/op = 000, r/m = 111 = [rdi]
47 db 0xf, 0xae, 00001110y ; mod = 00, reg/op = 001, r/m = 110 = [rsi]
52 global ASM_PFX(OrigVector)
53 global ASM_PFX(InterruptEntryStub)
54 global ASM_PFX(StubSize)
55 global ASM_PFX(CommonIdtEntry)
56 global ASM_PFX(FxStorSupport)
57 extern ASM_PFX(InterruptDistrubutionHub)
59 ASM_PFX(StubSize): dd InterruptEntryStubEnd - ASM_PFX(InterruptEntryStub)
60 AppRsp: dq 0x1111111111111111 ; ?
61 DebugRsp: dq 0x2222222222222222 ; ?
62 ExtraPush: dq 0x3333333333333333 ; ?
63 ExceptData: dq 0x4444444444444444 ; ?
64 Rflags: dq 0x5555555555555555 ; ?
65 ASM_PFX(OrigVector): dq 0x6666666666666666 ; ?
67 ;; The declarations below define the memory region that will be used for the debug stack.
68 ;; The context record will be built by pushing register values onto this stack.
69 ;; It is imparitive that alignment be carefully managed, since the FXSTOR and
70 ;; FXRSTOR instructions will GP fault if their memory operand is not 16 byte aligned.
72 ;; The stub will switch stacks from the application stack to the debuger stack
73 ;; and pushes the exception number.
75 ;; Then we building the context record on the stack. Since the stack grows down,
76 ;; we push the fields of the context record from the back to the front. There
77 ;; are 336 bytes of stack used prior allocating the 512 bytes of stack to be
78 ;; used as the memory buffer for the fxstor instruction. Therefore address of
79 ;; the buffer used for the FXSTOR instruction is &Eax - 336 - 512, which
80 ;; must be 16 byte aligned.
82 ;; We carefully locate the stack to make this happen.
84 ;; For reference, the context structure looks like this:
86 ;; UINT64 ExceptionData;
87 ;; FX_SAVE_STATE_X64 FxSaveState; // 512 bytes, must be 16 byte aligned
88 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
89 ;; UINT64 Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
92 ;; UINT64 Gdtr[2], Idtr[2];
94 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss;
95 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
96 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
97 ;; } SYSTEM_CONTEXT_X64; // 64 bit system context record
100 DebugStackEnd: db "DbgStkEnd >>>>>>" ;; 16 byte long string - must be 16 bytes to preserve alignment
101 times 0x1ffc dd 0x0 ;; 32K should be enough stack
102 ;; This allocation is coocked to insure
103 ;; that the the buffer for the FXSTORE instruction
104 ;; will be 16 byte aligned also.
106 ExceptionNumber: dq 0 ;; first entry will be the vector number pushed by the stub
108 DebugStackBegin: db "<<<< DbgStkBegin" ;; initial debug ESP == DebugStackBegin, set in stub
113 ;------------------------------------------------------------------------------
119 ; Abstract: Returns TRUE if FxStor instructions are supported
121 global ASM_PFX(FxStorSupport)
122 ASM_PFX(FxStorSupport):
125 ; cpuid corrupts rbx which must be preserved per the C calling convention
136 ;------------------------------------------------------------------------------
139 ; IA32_IDT_GATE_DESCRIPTOR * DestDesc, // rcx
140 ; void (*Vector) (void) // rdx
143 ; Abstract: Encodes an IDT descriptor with the given physical address
145 global ASM_PFX(Vect2Desc)
149 mov word [rcx], ax ; write bits 15..0 of offset
151 mov word [rcx+2], dx ; SYS_CODE_SEL from GDT
152 mov word [rcx+4], 0xe00 | 0x8000 ; type = 386 interrupt gate, present
154 mov word [rcx+6], ax ; write bits 31..16 of offset
156 mov dword [rcx+8], eax ; write bits 63..32 of offset
160 ;------------------------------------------------------------------------------
163 ; Abstract: This code is not a function, but is a small piece of code that is
164 ; copied and fixed up once for each IDT entry that is hooked.
166 ASM_PFX(InterruptEntryStub):
167 push 0 ; push vector number - will be modified before installed
169 dd 0 ; fixed up to relative address of CommonIdtEntry
170 InterruptEntryStubEnd:
172 ;------------------------------------------------------------------------------
175 ; Abstract: This code is not a function, but is the common part for all IDT
178 ASM_PFX(CommonIdtEntry):
180 ;; At this point, the stub has saved the current application stack esp into AppRsp
181 ;; and switched stacks to the debug stack, where it pushed the vector number
183 ;; The application stack looks like this:
186 ;; (last application stack entry)
187 ;; [16 bytes alignment, do not care it]
188 ;; SS from interrupted task
189 ;; RSP from interrupted task
190 ;; rflags from interrupted task
191 ;; CS from interrupted task
192 ;; RIP from interrupted task
193 ;; Error code <-------------------- Only present for some exeption types
195 ;; Vector Number <----------------- pushed in our IDT Entry
198 ;; The stub switched us to the debug stack and pushed the interrupt number.
200 ;; Next, construct the context record. It will be build on the debug stack by
201 ;; pushing the registers in the correct order so as to create the context structure
202 ;; on the debug stack. The context record must be built from the end back to the
203 ;; beginning because the stack grows down...
205 ;; For reference, the context record looks like this:
209 ;; UINT64 ExceptionData;
210 ;; FX_SAVE_STATE_X64 FxSaveState;
211 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
212 ;; UINT64 Cr0, Cr2, Cr3, Cr4, Cr8;
215 ;; UINT64 Gdtr[2], Idtr[2];
217 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss;
218 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
219 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
220 ;; } SYSTEM_CONTEXT_X64; // 64 bit system context record
222 ;; NOTE: we save rsp here to prevent compiler put rip reference cause error AppRsp
224 mov rax, qword [rsp+8] ; save vector number
225 mov [ExceptionNumber], rax ; save vector number
227 add rsp, 8 ; pop vector number
228 mov [AppRsp], rsp ; save stack top
229 lea rsp, [DebugStackBegin] ; switch to debugger stack
230 sub rsp, 8 ; leave space for vector number
232 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
233 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
251 ;; Save interrupt state rflags register...
256 ;; We need to determine if any extra data was pushed by the exception, and if so, save it
257 ;; To do this, we check the exception number pushed by the stub, and cache the
258 ;; result in a variable since we'll need this again.
259 cmp qword [ExceptionNumber], EXCPT64_DOUBLE_FAULT
261 cmp qword [ExceptionNumber], EXCPT64_INVALID_TSS
263 cmp qword [ExceptionNumber], EXCPT64_SEG_NOT_PRESENT
265 cmp qword [ExceptionNumber], EXCPT64_STACK_FAULT
267 cmp qword [ExceptionNumber], EXCPT64_GP_FAULT
269 cmp qword [ExceptionNumber], EXCPT64_PAGE_FAULT
271 cmp qword [ExceptionNumber], EXCPT64_ALIGNMENT_CHECK
273 mov qword [ExtraPush], 0
274 mov qword [ExceptData], 0
277 mov qword [ExtraPush], 1
279 ;; If there's some extra data, save it also, and modify the saved AppRsp to effectively
280 ;; pop this value off the application's stack.
283 mov qword [ExceptData], rbx
289 ;; The "push" above pushed the debug stack rsp. Since what we're actually doing
290 ;; is building the context record on the debug stack, we need to save the pushed
291 ;; debug RSP, and replace it with the application's last stack entry...
295 mov rax, QWORD [rax + 24]
296 ; application stack has ss, rsp, rflags, cs, & rip, so
297 ; last actual application stack entry is saved at offset
298 ; 24 bytes from stack top.
301 ;; continue building context record
302 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss; insure high 16 bits of each is zero
306 ; CS from application is one entry back in application stack
308 movzx rax, word [rax + 8]
321 ; Rip from application is on top of application stack
325 ;; UINT64 Gdtr[2], Idtr[2];
341 ;; Rflags from application is two entries back in application stack
343 push qword [rax + 16]
345 ;; UINT64 Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
346 ;; insure FXSAVE/FXRSTOR is enabled in CR4...
347 ;; ... while we're at it, make sure DE is also enabled...
362 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
365 ;; clear Dr7 while executing debugger itself
371 ;; insure all status bits in dr6 are clear...
384 ;; FX_SAVE_STATE_X64 FxSaveState;
387 ; IMPORTANT!! The debug stack has been carefully constructed to
388 ; insure that rsp and rdi are 16 byte aligned when we get here.
389 ; They MUST be. If they are not, a GP fault will occur.
392 ;; UEFI calling convention for x64 requires that Direction flag in EFLAGs is clear
395 ;; UINT64 ExceptionData;
396 mov rax, [ExceptData]
399 ; call to C code which will in turn call registered handler
400 ; pass in the vector number
402 mov rcx, [ExceptionNumber]
404 call ASM_PFX(InterruptDistrubutionHub)
408 ;; UINT64 ExceptionData;
411 ;; FX_SAVE_STATE_X64 FxSaveState;
416 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
425 ;; skip restore of dr6. We cleared dr6 during the context save.
430 ;; UINT64 Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
448 ;; UINT64 Gdtr[2], Idtr[2];
449 ;; Best not let anyone mess with these particular registers...
455 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss;
456 ;; NOTE - modified segment registers could hang the debugger... We
457 ;; could attempt to insulate ourselves against this possibility,
458 ;; but that poses risks as well.
474 ;; The next stuff to restore is the general purpose registers that were pushed
475 ;; using the "push" instruction.
477 ;; The value of RSP as stored in the context record is the application RSP
478 ;; including the 5 entries on the application stack caused by the exception
479 ;; itself. It may have been modified by the debug agent, so we need to
480 ;; determine if we need to relocate the application stack.
482 mov rbx, [rsp + 24] ; move the potentially modified AppRsp into rbx
484 mov rax, QWORD [rax + 24]
492 mov rcx, [rax + 8] ; CS
495 mov rcx, [rax + 16] ; RFLAGS
498 mov rcx, [rax + 24] ; RSP
501 mov rcx, [rax + 32] ; SS
504 mov rax, rbx ; modify the saved AppRsp to the new AppRsp
507 mov rax, [DebugRsp] ; restore the DebugRsp on the debug stack
508 ; so our "pop" will not cause a stack switch
511 cmp qword [ExceptionNumber], 0x68
516 ;; Restore rflags so when we chain, the flags will be exactly as if we were never here.
517 ;; We gin up the stack to do an iretq so we can get ALL the flags.
528 and rbx, ~ 0x300 ; special handling for IF and TF
532 lea rax, [PhonyIretq]
537 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
538 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
556 ;; Switch back to application stack
559 ;; Jump to original handler
560 jmp [ASM_PFX(OrigVector)]
563 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
564 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
582 ;; Switch back to application stack
585 ;; We're outa here...