2 ; Low level x64 routines used by the debug support driver.
4 ; Copyright (c) 2007 - 2008, Intel Corporation.
5 ; All rights reserved. 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 EXCPT64_DIVIDE_ERROR EQU 0
18 EXCPT64_BREAKPOINT EQU 3
19 EXCPT64_OVERFLOW EQU 4
21 EXCPT64_INVALID_OPCODE EQU 6
22 EXCPT64_DOUBLE_FAULT EQU 8
23 EXCPT64_INVALID_TSS EQU 10
24 EXCPT64_SEG_NOT_PRESENT EQU 11
25 EXCPT64_STACK_FAULT EQU 12
26 EXCPT64_GP_FAULT EQU 13
27 EXCPT64_PAGE_FAULT EQU 14
28 EXCPT64_FP_ERROR EQU 16
29 EXCPT64_ALIGNMENT_CHECK EQU 17
30 EXCPT64_MACHINE_CHECK EQU 18
33 FXSTOR_FLAG EQU 01000000h ; 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 0fh, 0aeh, 00000111y ; mod = 00, reg/op = 000, r/m = 111 = [rdi]
47 db 0fh, 0aeh, 00001110y ; mod = 00, reg/op = 001, r/m = 110 = [rsi]
52 public OrigVector, InterruptEntryStub, StubSize, CommonIdtEntry, FxStorSupport
54 StubSize dd InterruptEntryStubEnd - InterruptEntryStub
55 AppRsp dq 1111111111111111h ; ?
56 DebugRsp dq 2222222222222222h ; ?
57 ExtraPush dq 3333333333333333h ; ?
58 ExceptData dq 4444444444444444h ; ?
59 Rflags dq 5555555555555555h ; ?
60 OrigVector dq 6666666666666666h ; ?
62 ;; The declarations below define the memory region that will be used for the debug stack.
63 ;; The context record will be built by pushing register values onto this stack.
64 ;; It is imparitive that alignment be carefully managed, since the FXSTOR and
65 ;; FXRSTOR instructions will GP fault if their memory operand is not 16 byte aligned.
67 ;; The stub will switch stacks from the application stack to the debuger stack
68 ;; and pushes the exception number.
70 ;; Then we building the context record on the stack. Since the stack grows down,
71 ;; we push the fields of the context record from the back to the front. There
72 ;; are 336 bytes of stack used prior allocating the 512 bytes of stack to be
73 ;; used as the memory buffer for the fxstor instruction. Therefore address of
74 ;; the buffer used for the FXSTOR instruction is &Eax - 336 - 512, which
75 ;; must be 16 byte aligned.
77 ;; We carefully locate the stack to make this happen.
79 ;; For reference, the context structure looks like this:
81 ;; UINT64 ExceptionData;
82 ;; FX_SAVE_STATE_X64 FxSaveState; // 512 bytes, must be 16 byte aligned
83 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
84 ;; UINT64 Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
87 ;; UINT64 Gdtr[2], Idtr[2];
89 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss;
90 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
91 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
92 ;; } SYSTEM_CONTEXT_X64; // 64 bit system context record
95 DebugStackEnd db "DbgStkEnd >>>>>>" ;; 16 byte long string - must be 16 bytes to preserve alignment
96 dd 1ffch dup (000000000h) ;; 32K should be enough stack
97 ;; This allocation is coocked to insure
98 ;; that the the buffer for the FXSTORE instruction
99 ;; will be 16 byte aligned also.
101 ExceptionNumber dq ? ;; first entry will be the vector number pushed by the stub
103 DebugStackBegin db "<<<< DbgStkBegin" ;; initial debug ESP == DebugStackBegin, set in stub
109 externdef InterruptDistrubutionHub:near
111 ;------------------------------------------------------------------------------
117 ; Abstract: Returns TRUE if FxStor instructions are supported
119 FxStorSupport PROC PUBLIC
122 ; cpuid corrupts rbx which must be preserved per the C calling convention
134 ;------------------------------------------------------------------------------
137 ; IA32_IDT_GATE_DESCRIPTOR * DestDesc, // rcx
138 ; void (*Vector) (void) // rdx
141 ; Abstract: Encodes an IDT descriptor with the given physical address
143 Vect2Desc PROC PUBLIC
146 mov word ptr [rcx], ax ; write bits 15..0 of offset
148 mov word ptr [rcx+2], dx ; SYS_CODE_SEL from GDT
149 mov word ptr [rcx+4], 0e00h OR 8000h ; type = 386 interrupt gate, present
151 mov word ptr [rcx+6], ax ; write bits 31..16 of offset
153 mov dword ptr [rcx+8], eax ; write bits 63..32 of offset
161 ;------------------------------------------------------------------------------
164 ; Abstract: This code is not a function, but is a small piece of code that is
165 ; copied and fixed up once for each IDT entry that is hooked.
168 push 0 ; push vector number - will be modified before installed
170 dd 0 ; fixed up to relative address of CommonIdtEntry
171 InterruptEntryStubEnd:
175 ;------------------------------------------------------------------------------
178 ; Abstract: This code is not a function, but is the common part for all IDT
183 ;; At this point, the stub has saved the current application stack esp into AppRsp
184 ;; and switched stacks to the debug stack, where it pushed the vector number
186 ;; The application stack looks like this:
189 ;; (last application stack entry)
190 ;; [16 bytes alignment, do not care it]
191 ;; SS from interrupted task
192 ;; RSP from interrupted task
193 ;; rflags from interrupted task
194 ;; CS from interrupted task
195 ;; RIP from interrupted task
196 ;; Error code <-------------------- Only present for some exeption types
198 ;; Vector Number <----------------- pushed in our IDT Entry
202 ;; The stub switched us to the debug stack and pushed the interrupt number.
204 ;; Next, construct the context record. It will be build on the debug stack by
205 ;; pushing the registers in the correct order so as to create the context structure
206 ;; on the debug stack. The context record must be built from the end back to the
207 ;; beginning because the stack grows down...
209 ;; For reference, the context record looks like this:
213 ;; UINT64 ExceptionData;
214 ;; FX_SAVE_STATE_X64 FxSaveState;
215 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
216 ;; UINT64 Cr0, Cr2, Cr3, Cr4, Cr8;
219 ;; UINT64 Gdtr[2], Idtr[2];
221 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss;
222 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
223 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
224 ;; } SYSTEM_CONTEXT_X64; // 64 bit system context record
226 ;; NOTE: we save rsp here to prevent compiler put rip reference cause error AppRsp
228 mov rax, qword ptr [rsp][8] ; save vector number
229 mov ExceptionNumber, rax ; save vector number
231 add rsp, 8 ; pop vector number
232 mov AppRsp, rsp ; save stack top
233 mov rsp, offset DebugStackBegin ; switch to debugger stack
234 sub rsp, 8 ; leave space for vector number
236 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
237 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
255 ;; Save interrupt state rflags register...
258 mov qword ptr Rflags, rax
260 ;; We need to determine if any extra data was pushed by the exception, and if so, save it
261 ;; To do this, we check the exception number pushed by the stub, and cache the
262 ;; result in a variable since we'll need this again.
263 cmp ExceptionNumber, EXCPT64_DOUBLE_FAULT
265 cmp ExceptionNumber, EXCPT64_INVALID_TSS
267 cmp ExceptionNumber, EXCPT64_SEG_NOT_PRESENT
269 cmp ExceptionNumber, EXCPT64_STACK_FAULT
271 cmp ExceptionNumber, EXCPT64_GP_FAULT
273 cmp ExceptionNumber, EXCPT64_PAGE_FAULT
275 cmp ExceptionNumber, EXCPT64_ALIGNMENT_CHECK
283 ;; If there's some extra data, save it also, and modify the saved AppRsp to effectively
284 ;; pop this value off the application's stack.
293 ;; The "push" above pushed the debug stack rsp. Since what we're actually doing
294 ;; is building the context record on the debug stack, we need to save the pushed
295 ;; debug RSP, and replace it with the application's last stack entry...
300 ; application stack has ss, rsp, rflags, cs, & rip, so
301 ; last actual application stack entry is
302 ; 40 bytes into the application stack.
305 ;; continue building context record
306 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss; insure high 16 bits of each is zero
310 ; CS from application is one entry back in application stack
312 movzx rax, word ptr [rax + 8]
325 ; Rip from application is on top of application stack
329 ;; UINT64 Gdtr[2], Idtr[2];
345 ;; Rflags from application is two entries back in application stack
347 push qword ptr [rax + 16]
349 ;; UINT64 Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
350 ;; insure FXSAVE/FXRSTOR is enabled in CR4...
351 ;; ... while we're at it, make sure DE is also enabled...
366 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
369 ;; clear Dr7 while executing debugger itself
375 ;; insure all status bits in dr6 are clear...
388 ;; FX_SAVE_STATE_X64 FxSaveState;
391 ; IMPORTANT!! The debug stack has been carefully constructed to
392 ; insure that rsp and rdi are 16 byte aligned when we get here.
393 ; They MUST be. If they are not, a GP fault will occur.
396 ;; UINT64 ExceptionData;
400 ; call to C code which will in turn call registered handler
401 ; pass in the vector number
403 mov rcx, ExceptionNumber
405 call InterruptDistrubutionHub
409 ;; UINT64 ExceptionData;
412 ;; FX_SAVE_STATE_X64 FxSaveState;
417 ;; UINT64 Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
426 ;; skip restore of dr6. We cleared dr6 during the context save.
431 ;; UINT64 Cr0, Cr1, Cr2, Cr3, Cr4, Cr8;
446 pop qword ptr [rax + 16]
449 ;; UINT64 Gdtr[2], Idtr[2];
450 ;; Best not let anyone mess with these particular registers...
456 ;; UINT64 Gs, Fs, Es, Ds, Cs, Ss;
457 ;; NOTE - modified segment registers could hang the debugger... We
458 ;; could attempt to insulate ourselves against this possibility,
459 ;; but that poses risks as well.
471 pop qword ptr [rax + 8]
475 ;; The next stuff to restore is the general purpose registers that were pushed
476 ;; using the "push" instruction.
478 ;; The value of RSP as stored in the context record is the application RSP
479 ;; including the 5 entries on the application stack caused by the exception
480 ;; itself. It may have been modified by the debug agent, so we need to
481 ;; determine if we need to relocate the application stack.
483 mov rbx, [rsp + 24] ; move the potentially modified AppRsp into rbx
493 mov rcx, [rax + 8] ; CS
496 mov rcx, [rax + 16] ; RFLAGS
499 mov rcx, [rax + 24] ; RSP
502 mov rcx, [rax + 32] ; SS
505 mov rax, rbx ; modify the saved AppRsp to the new AppRsp
508 mov rax, DebugRsp ; restore the DebugRsp on the debug stack
509 ; so our "pop" will not cause a stack switch
512 cmp ExceptionNumber, 068h
517 ;; Restore rflags so when we chain, the flags will be exactly as if we were never here.
518 ;; We gin up the stack to do an iretq so we can get ALL the flags.
529 and rbx, NOT 300h ; special handling for IF and TF
533 mov rax, offset PhonyIretq
538 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
539 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
557 ;; Switch back to application stack
560 ;; Jump to original handler
564 ;; UINT64 Rdi, Rsi, Rbp, Rsp, Rbx, Rdx, Rcx, Rax;
565 ;; UINT64 R8, R9, R10, R11, R12, R13, R14, R15;
583 ;; Switch back to application stack
586 ;; We're outa here...