2 ; Low level x64 routines used by the debug support driver.
4 ; Copyright (c) 2007 - 2018, Intel Corporation. All rights reserved.<BR>
5 ; SPDX-License-Identifier: BSD-2-Clause-Patent
9 %define EXCPT64_DIVIDE_ERROR 0
10 %define EXCPT64_DEBUG 1
12 %define EXCPT64_BREAKPOINT 3
13 %define EXCPT64_OVERFLOW 4
14 %define EXCPT64_BOUND 5
15 %define EXCPT64_INVALID_OPCODE 6
16 %define EXCPT64_DOUBLE_FAULT 8
17 %define EXCPT64_INVALID_TSS 10
18 %define EXCPT64_SEG_NOT_PRESENT 11
19 %define EXCPT64_STACK_FAULT 12
20 %define EXCPT64_GP_FAULT 13
21 %define EXCPT64_PAGE_FAULT 14
22 %define EXCPT64_FP_ERROR 16
23 %define EXCPT64_ALIGNMENT_CHECK 17
24 %define EXCPT64_MACHINE_CHECK 18
25 %define EXCPT64_SIMD 19
27 %define FXSTOR_FLAG 0x1000000 ; bit cpuid 24 of feature flags
29 ;; The FXSTOR and FXRSTOR commands are used for saving and restoring the x87,
30 ;; MMX, SSE, SSE2, etc registers. The initialization of the debugsupport driver
31 ;; MUST check the CPUID feature flags to see that these instructions are available
32 ;; and fail to init if they are not.
36 db 0xf, 0xae, 00000111y ; mod = 00, reg/op = 000, r/m = 111 = [rdi]
41 db 0xf, 0xae, 00001110y ; mod = 00, reg/op = 001, r/m = 110 = [rsi]
46 global ASM_PFX(OrigVector)
47 global ASM_PFX(InterruptEntryStub)
48 global ASM_PFX(StubSize)
49 global ASM_PFX(CommonIdtEntry)
50 global ASM_PFX(FxStorSupport)
51 extern ASM_PFX(InterruptDistrubutionHub)
53 ASM_PFX(StubSize): dd InterruptEntryStubEnd - ASM_PFX(InterruptEntryStub)
54 AppRsp: dq 0x1111111111111111 ; ?
55 DebugRsp: dq 0x2222222222222222 ; ?
56 ExtraPush: dq 0x3333333333333333 ; ?
57 ExceptData: dq 0x4444444444444444 ; ?
58 Rflags: dq 0x5555555555555555 ; ?
59 ASM_PFX(OrigVector): dq 0x6666666666666666 ; ?
61 ;; The declarations below define the memory region that will be used for the debug stack.
62 ;; The context record will be built by pushing register values onto this stack.
63 ;; It is imparitive that alignment be carefully managed, since the FXSTOR and
64 ;; FXRSTOR instructions will GP fault if their memory operand is not 16 byte aligned.
66 ;; The stub will switch stacks from the application stack to the debuger stack
67 ;; and pushes the exception number.
69 ;; Then we building the context record on the stack. Since the stack grows down,
70 ;; we push the fields of the context record from the back to the front. There
71 ;; are 336 bytes of stack used prior allocating the 512 bytes of stack to be
72 ;; used as the memory buffer for the fxstor instruction. Therefore address of
73 ;; the buffer used for the FXSTOR instruction is &Eax - 336 - 512, which
74 ;; must be 16 byte aligned.
76 ;; We carefully locate the stack to make this happen.
78 ;; For reference, the context structure looks like this:
80 ;; UINT64 ExceptionData;
81 ;; FX_SAVE_STATE_X64 FxSaveState; // 512 bytes, must be 16 byte aligned
82 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
83 ;; UINT64 Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
86 ;; UINT64 Gdtr[2], Idtr[2];
88 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss;
89 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
90 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
91 ;; } SYSTEM_CONTEXT_X64; // 64 bit system context record
94 DebugStackEnd: db "DbgStkEnd >>>>>>" ;; 16 byte long string - must be 16 bytes to preserve alignment
95 times 0x1ffc dd 0x0 ;; 32K should be enough stack
96 ;; This allocation is coocked to insure
97 ;; that the the buffer for the FXSTORE instruction
98 ;; will be 16 byte aligned also.
100 ExceptionNumber: dq 0 ;; first entry will be the vector number pushed by the stub
102 DebugStackBegin: db "<<<< DbgStkBegin" ;; initial debug ESP == DebugStackBegin, set in stub
107 ;------------------------------------------------------------------------------
113 ; Abstract: Returns TRUE if FxStor instructions are supported
115 global ASM_PFX(FxStorSupport)
116 ASM_PFX(FxStorSupport):
119 ; cpuid corrupts rbx which must be preserved per the C calling convention
130 ;------------------------------------------------------------------------------
133 ; IA32_IDT_GATE_DESCRIPTOR * DestDesc, // rcx
134 ; void (*Vector) (void) // rdx
137 ; Abstract: Encodes an IDT descriptor with the given physical address
139 global ASM_PFX(Vect2Desc)
143 mov word [rcx], ax ; write bits 15..0 of offset
145 mov word [rcx+2], dx ; SYS_CODE_SEL from GDT
146 mov word [rcx+4], 0xe00 | 0x8000 ; type = 386 interrupt gate, present
148 mov word [rcx+6], ax ; write bits 31..16 of offset
150 mov dword [rcx+8], eax ; write bits 63..32 of offset
154 ;------------------------------------------------------------------------------
157 ; Abstract: This code is not a function, but is a small piece of code that is
158 ; copied and fixed up once for each IDT entry that is hooked.
160 ASM_PFX(InterruptEntryStub):
161 push 0 ; push vector number - will be modified before installed
163 dd 0 ; fixed up to relative address of CommonIdtEntry
164 InterruptEntryStubEnd:
166 ;------------------------------------------------------------------------------
169 ; Abstract: This code is not a function, but is the common part for all IDT
172 ASM_PFX(CommonIdtEntry):
174 ;; At this point, the stub has saved the current application stack esp into AppRsp
175 ;; and switched stacks to the debug stack, where it pushed the vector number
177 ;; The application stack looks like this:
180 ;; (last application stack entry)
181 ;; [16 bytes alignment, do not care it]
182 ;; SS from interrupted task
183 ;; RSP from interrupted task
184 ;; rflags from interrupted task
185 ;; CS from interrupted task
186 ;; RIP from interrupted task
187 ;; Error code <-------------------- Only present for some exeption types
189 ;; Vector Number <----------------- pushed in our IDT Entry
192 ;; The stub switched us to the debug stack and pushed the interrupt number.
194 ;; Next, construct the context record. It will be build on the debug stack by
195 ;; pushing the registers in the correct order so as to create the context structure
196 ;; on the debug stack. The context record must be built from the end back to the
197 ;; beginning because the stack grows down...
199 ;; For reference, the context record looks like this:
203 ;; UINT64 ExceptionData;
204 ;; FX_SAVE_STATE_X64 FxSaveState;
205 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
206 ;; UINT64 Cr0, Cr2, Cr3, Cr4, Cr8;
209 ;; UINT64 Gdtr[2], Idtr[2];
211 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss;
212 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
213 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
214 ;; } SYSTEM_CONTEXT_X64; // 64 bit system context record
216 ;; NOTE: we save rsp here to prevent compiler put rip reference cause error AppRsp
218 mov rax, qword [rsp+8] ; save vector number
219 mov [ExceptionNumber], rax ; save vector number
221 add rsp, 8 ; pop vector number
222 mov [AppRsp], rsp ; save stack top
223 lea rsp, [DebugStackBegin] ; switch to debugger stack
224 sub rsp, 8 ; leave space for vector number
226 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
227 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
245 ;; Save interrupt state rflags register...
250 ;; We need to determine if any extra data was pushed by the exception, and if so, save it
251 ;; To do this, we check the exception number pushed by the stub, and cache the
252 ;; result in a variable since we'll need this again.
253 cmp qword [ExceptionNumber], EXCPT64_DOUBLE_FAULT
255 cmp qword [ExceptionNumber], EXCPT64_INVALID_TSS
257 cmp qword [ExceptionNumber], EXCPT64_SEG_NOT_PRESENT
259 cmp qword [ExceptionNumber], EXCPT64_STACK_FAULT
261 cmp qword [ExceptionNumber], EXCPT64_GP_FAULT
263 cmp qword [ExceptionNumber], EXCPT64_PAGE_FAULT
265 cmp qword [ExceptionNumber], EXCPT64_ALIGNMENT_CHECK
267 mov qword [ExtraPush], 0
268 mov qword [ExceptData], 0
271 mov qword [ExtraPush], 1
273 ;; If there's some extra data, save it also, and modify the saved AppRsp to effectively
274 ;; pop this value off the application's stack.
277 mov qword [ExceptData], rbx
283 ;; The "push" above pushed the debug stack rsp. Since what we're actually doing
284 ;; is building the context record on the debug stack, we need to save the pushed
285 ;; debug RSP, and replace it with the application's last stack entry...
289 mov rax, QWORD [rax + 24]
290 ; application stack has ss, rsp, rflags, cs, & rip, so
291 ; last actual application stack entry is saved at offset
292 ; 24 bytes from stack top.
295 ;; continue building context record
296 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss; insure high 16 bits of each is zero
300 ; CS from application is one entry back in application stack
302 movzx rax, word [rax + 8]
315 ; Rip from application is on top of application stack
319 ;; UINT64 Gdtr[2], Idtr[2];
335 ;; Rflags from application is two entries back in application stack
337 push qword [rax + 16]
339 ;; UINT64 Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
340 ;; insure FXSAVE/FXRSTOR is enabled in CR4...
341 ;; ... while we're at it, make sure DE is also enabled...
356 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
359 ;; clear Dr7 while executing debugger itself
365 ;; insure all status bits in dr6 are clear...
378 ;; FX_SAVE_STATE_X64 FxSaveState;
381 ; IMPORTANT!! The debug stack has been carefully constructed to
382 ; insure that rsp and rdi are 16 byte aligned when we get here.
383 ; They MUST be. If they are not, a GP fault will occur.
386 ;; UEFI calling convention for x64 requires that Direction flag in EFLAGs is clear
389 ;; UINT64 ExceptionData;
390 mov rax, [ExceptData]
393 ; call to C code which will in turn call registered handler
394 ; pass in the vector number
396 mov rcx, [ExceptionNumber]
398 call ASM_PFX(InterruptDistrubutionHub)
402 ;; UINT64 ExceptionData;
405 ;; FX_SAVE_STATE_X64 FxSaveState;
410 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
419 ;; skip restore of dr6. We cleared dr6 during the context save.
424 ;; UINT64 Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
442 ;; UINT64 Gdtr[2], Idtr[2];
443 ;; Best not let anyone mess with these particular registers...
449 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss;
450 ;; NOTE - modified segment registers could hang the debugger... We
451 ;; could attempt to insulate ourselves against this possibility,
452 ;; but that poses risks as well.
468 ;; The next stuff to restore is the general purpose registers that were pushed
469 ;; using the "push" instruction.
471 ;; The value of RSP as stored in the context record is the application RSP
472 ;; including the 5 entries on the application stack caused by the exception
473 ;; itself. It may have been modified by the debug agent, so we need to
474 ;; determine if we need to relocate the application stack.
476 mov rbx, [rsp + 24] ; move the potentially modified AppRsp into rbx
478 mov rax, QWORD [rax + 24]
486 mov rcx, [rax + 8] ; CS
489 mov rcx, [rax + 16] ; RFLAGS
492 mov rcx, [rax + 24] ; RSP
495 mov rcx, [rax + 32] ; SS
498 mov rax, rbx ; modify the saved AppRsp to the new AppRsp
501 mov rax, [DebugRsp] ; restore the DebugRsp on the debug stack
502 ; so our "pop" will not cause a stack switch
505 cmp qword [ExceptionNumber], 0x68
510 ;; Restore rflags so when we chain, the flags will be exactly as if we were never here.
511 ;; We gin up the stack to do an iretq so we can get ALL the flags.
522 and rbx, ~ 0x300 ; special handling for IF and TF
526 lea rax, [PhonyIretq]
531 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
532 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
550 ;; Switch back to application stack
553 ;; Jump to original handler
554 jmp [ASM_PFX(OrigVector)]
557 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
558 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
576 ;; Switch back to application stack
579 ;; We're outa here...