Re: [PING][PING] Added x86_64 stub for debugging embedded systems running on Intel x86_64 processor architecture.

Battig, Caleb
2020-10-20T16:34:37Z

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Simon,

Thanks for getting back to me. I am unfortunately unable to use 'gdb send-email' to send git patches. This is because my organization requires two factor authentication for Outlook (our email client) and I don't think Git Credential Manager can be setup with 2fa. For instance -

Send this email? ([y]es|[n]o|[q]uit|[a]ll): y
5.7.3 Authentication unsuccessful [SA0PR11CA0047.namprd11.prod.outlook.com]

The GDB Contribution Checklist - https://sourceware.org/gdb/wiki/ContributionChecklist#Submitting_patches - says, "If using git send-email is not possible for you, you can still try to send it using your email client, pasting the output of git format-patch in the email body." So I have opted for this instead.

I have cleaned up all the whitespace coding standard violations. See the attachment.

Thanks,

Caleb Battig

Platform Software Engineer

NetApp

724.741.5226 Direct Phone

Caleb.Battig@netapp.com<mailto:Eugene.Novak@netapp.com>

netapp.com<http://www.netapp.com/us/>

[cid:1f8fcc99-6da2-4a8a-8f86-465d04044777]

________________________________
From: Simon Marchi <simark@simark.ca>
Sent: Tuesday, October 20, 2020 7:09 AM
To: Battig, Caleb <Caleb.Battig@netapp.com>; gdb-patches@sourceware.org <gdb-patches@sourceware.org>
Cc: Lovett, Stuart <Stuart.Lovett@netapp.com>; Peikes, Wendy <Wendy.Peikes@netapp.com>
Subject: Re: [PING][PING] Added x86_64 stub for debugging embedded systems running on Intel x86_64 processor architecture.

NetApp Security WARNING: This is an external email. Do not click links or open attachments unless you recognize the sender and know the content is safe.

On 2020-10-19 6:23 p.m., Battig, Caleb wrote:
> Simon,
>
> Thanks so much for looking into this. This is a significant addition to GDB that has the potential to help a lot of developers.
>
> I've made some formatting changes. See the attached patch. I'm not sure what you meant by your comment on whitespace and indentation, but I made all the other changes.
>
> Thanks,

For example, if a line is indented by 18 columns, that means you'll have
two tabs (worth 16 columns) followed by two spaces (for a total of 18
columns).

You can find the faulty lines using:

$ grep -E '^\t* ' x86_64-stub.c

Can you please send your patch using git-send-email? It's not
convenient to send in-line comments for a patch sent as attachment.

"if" blocks should be formatted like this:

if (something)
{
..
}

"if" blocks that contain a single line don't need braces. The exception
is if you ou have nested "if" blocks, the outer ones need to have
braces:

if (something)
printf ("Something");

but:

if (something)
{
if (something_else)
printf ("Something 1");
}
else
printf ("Something 2");

Thanks,

Simon

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From ea6b0e3ed665ffb3aa18fdc535aeb1247eaabacc Mon Sep 17 00:00:00 2001
From: Caleb Battig <caleb.battig@netapp.com>
Date: Tue, 20 Oct 2020 10:29:14 -0600
Subject: [PATCH] Added-x86_64 stub for debugging embedded systems running
Intel x86_64 architecture.

---
gdb/stubs/x86_64-stub.c | 1272 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 1272 insertions(+)
create mode 100644 gdb/stubs/x86_64-stub.c

diff --git a/gdb/stubs/x86_64-stub.c b/gdb/stubs/x86_64-stub.c
new file mode 100644
index 0000000000..eaf523a237
--- /dev/null
+++ b/gdb/stubs/x86_64-stub.c
@@ -0,0 +1,1272 @@
+/****************************************************************************
+
+ THIS SOFTWARE IS NOT COPYRIGHTED
+
+ HP offers the following for use in the public domain. HP makes no
+ warranty with regard to the software or it's performance and the
+ user accepts the software "AS IS" with all faults.
+
+ HP DISCLAIMS ANY WARRANTIES, EXPRESS OR IMPLIED, WITH REGARD
+ TO THIS SOFTWARE INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+ OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+
+****************************************************************************/
+
+/****************************************************************************
+ * Header: remcom.c,v 1.34 91/03/09 12:29:49 glenne Exp $
+ *
+ * Module name: remcom.c $
+ * Revision: 1.34 $
+ * Date: 91/03/09 12:29:49 $
+ * Contributor: Lake Stevens Instrument Division$
+ *
+ * Description: low level support for gdb debugger. $
+ *
+ * Considerations: only works on target hardware $
+ *
+ * Written by: Glenn Engel $
+ * ModuleState: Experimental $
+ *
+ * NOTES: See Below $
+ *
+ * Modified for 386 by Jim Kingdon, Cygnus Support.
+ *
+ * To enable debugger support, two things need to happen. One, a
+ * call to set_debug_traps() is necessary in order to allow any breakpoints
+ * or error conditions to be properly intercepted and reported to gdb.
+ * Two, a breakpoint needs to be generated to begin communication. This
+ * is most easily accomplished by a call to breakpoint(). Breakpoint()
+ * simulates a breakpoint by executing a trap #1.
+ *
+ * The function exceptionHandler () is
+ * used to attach a specific handler to a specific 386 vector number.
+ * It should use the same privilege level it runs at. It should
+ * install it as an interrupt gate so that interrupts are masked
+ * while the handler runs.
+ *
+ * Because gdb will sometimes write to the stack area to execute function
+ * calls, this program cannot rely on using the supervisor stack so it
+ * uses it's own stack area reserved in the int array remcomStack.
+ *
+ *************
+ *
+ * The following gdb commands are supported:
+ *
+ * command function Return value
+ *
+ * g return the value of the CPU _registers hex data or ENN
+ * G set the value of the CPU _registers OK or ENN
+ *
+ * mAA..AA,LLLL Read LLLL bytes at address AA..AA hex data or ENN
+ * MAA..AA,LLLL: Write LLLL bytes at address AA.AA OK or ENN
+ *
+ * c Resume at current address SNN ( signal NN)
+ * cAA..AA Continue at address AA..AA SNN
+ *
+ * s Step one instruction SNN
+ * sAA..AA Step one instruction from AA..AA SNN
+ *
+ * k kill
+ *
+ * ? What was the last sigval ? SNN (signal NN)
+ *
+ * All commands and responses are sent with a packet which includes a
+ * checksum. A packet consists of
+ *
+ * $<packet info>#<checksum>.
+ *
+ * where
+ * <packet info> :: <characters representing the command or response>
+ * <checksum> :: < two hex digits computed as modulo 256 sum of <packetinfo>>
+ *
+ * When a packet is received, it is first acknowledged with either '+' or '-'.
+ * '+' indicates a successful transfer. '-' indicates a failed transfer.
+ *
+ * Example:
+ *
+ * Host: Reply:
+ * $m0,10#2a +$00010203040506070809101112131415#42
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ *
+ * Update 2020/03/05
+ *
+ * This stub is based on the old x86 stub (i386-stub.c) provided by gdb.
+ * It has been updated to support intel x86_64 processor architecture.
+ *
+ ****************************************************************************/
+
+/*
+ * We don't want GCC to compile this file with any optimizations since
+ * it contains so much embedded x64 assembly code.
+ */
+#pragma GCC optimize("-O0")
+
+#include <stdio.h>
+#include <string.h>
+
+/* single threaded target */
+#define THREAD_TID "1"
+
+/************************************************************************
+ *
+ * External low-level support routines.
+ * These functions should have an OS specific implementation provided.
+ * See - https://sourceware.org/gdb/onlinedocs/gdb/Bootstrapping.html#Bootstrapping.
+ *
+ * For convenience, default implementations of these functions are provided at the
+ * end of this file, but they may not apply to your OS. To enable the default
+ * implementations uncomment the below defines:
+ *
+ * #define GDB_USE_SERIAL_PORT_IO // for the functions putDebugChar() and getDebugChar()
+ * #define GDB_USE_STD_X64_EXCEPTION_HANDLER // for the function exceptionHandler()
+ */
+extern void putDebugChar (char c); /* write a single character */
+extern int getDebugChar (void); /* read and return a single char */
+extern void exceptionHandler (int intr_vector, void *intr_handler); /* install intr_handler as handler for exception intr_vector */
+/************************************************************************/
+
+/************************************************************************
+ * Internal support routines
+ */
+static char *gdb_strcpy (char *dest, const char *src); /* essentially strcpy */
+static void gdb_bcopy (void *from, void *to, int length);
+static int gdb_str_starts_with (char *str, char *prefix);
+static size_t gdb_run_length_encode (char *buffer, size_t length);
+/************************************************************************/
+
+/* BUFMAX defines the maximum number of characters in inbound/outbound buffers*/
+/* at least NUMREGBYTES*2 are needed for register packets */
+#define BUFMAX 1024
+
+static char initialized = 0; /* boolean flag. != 0 means we've been initialized */
+static const char hexchars[] = "0123456789abcdef";
+
+/*
+ * GDB expects the 16-bit segment registers (%cs, %ss, %ds, %es, %fs, %gs)
+ * as well as the 64-bit rflags register to be stored in 32-bit fields.
+ * So we need to separate the registers into two arrays.
+ */
+
+/* Number of non-segment registers. */
+#define NUMREGS 17
+/* Number of segment registers. */
+#define NUMSEGREGS 7
+
+/* Number of bytes of 64-bit registers. */
+#define NUMREGBYTES (NUMREGS * 8)
+/* Need to store the segment registers in 32-bit fields. */
+#define NUMSEGREGBYTES (NUMSEGREGS * 4)
+
+/* Names of 64-bit registers */
+enum regnames { RAX, RBX, RCX, RDX, RSI, RDI, RBP, RSP,
+ R8, R9, R10, R11, R12, R13, R14, R15,
+ RIP };
+/*
+ * Names of 16-bit segment registers.
+ * rflags is included here because GDB expects it to be stored
+ * in a 32-bit field
+ */
+enum segregnames { PS /* also known as rflags */, CS, SS, DS, ES, FS, GS };
+
+/*
+ * These should not be static because they can be used outside this module
+ */
+uint64_t _registers[NUMREGS];
+uint32_t _segregisters[NUMSEGREGS];
+
+#define STACKSIZE 10000
+uint64_t remcomStack[STACKSIZE/sizeof(uint64_t)];
+static uint64_t* _stackPtr = &remcomStack[STACKSIZE/sizeof(uint64_t) - 1];
+
+
+/*************************** ASSEMBLY CODE MACROS *************************/
+
+extern void
+_return_to_prog ();
+
+/* Restore the program's _registers (including the stack pointer, which
+ means we get the right stack and don't have to worry about popping our
+ return address and any stack frames and so on) and return. */
+asm(".text");
+asm(".globl _return_to_prog");
+asm("_return_to_prog:");
+ asm("movw _segregisters+8, %ss");
+ asm("movq _registers+56, %rsp");
+ asm("movq _registers+8, %rbx");
+ asm("movq _registers+16, %rcx");
+ asm("movq _registers+24, %rdx");
+ asm("movq _registers+32, %rsi");
+ asm("movq _registers+40, %rdi");
+ asm("movq _registers+48, %rbp");
+ asm("movq _registers+64, %r8");
+ asm("movq _registers+72, %r9");
+ asm("movq _registers+80, %r10");
+ asm("movq _registers+88, %r11");
+ asm("movq _registers+96, %r12");
+ asm("movq _registers+104, %r13");
+ asm("movq _registers+112, %r14");
+ asm("movq _registers+120, %r15");
+ asm("movw _segregisters+12, %ds");
+ asm("movw _segregisters+16, %es");
+ asm("movw _segregisters+20, %fs");
+ asm("movw _segregisters+24, %gs");
+ asm("xorq %rax, %rax");
+ asm("movl _segregisters, %eax");
+ asm("pushq %rax"); /* saved rflags */
+ asm("movl _segregisters+4, %eax");
+ asm("pushq %rax"); /* saved cs */
+ asm("movq _registers+128, %rax");
+ asm("pushq %rax"); /* saved rip */
+ asm("movq _registers, %rax");
+ /* use iretq to restore rip and rflags together so
+ that trace flag works right. */
+ asm("iretq");
+
+#define BREAKPOINT() asm(" int $3")
+
+/* Put the error code here just in case the user cares. */
+uint64_t _gdb_errcode;
+/* Likewise, the vector number here (since GDB only gets the signal
+ number through the usual means, and that's not very specific). */
+uint64_t gdb_vector = -1;
+
+/* GDB stores segment _registers in 32-bit words (that's just the way
+ m-i386v.h is written). So zero the appropriate areas in _segregisters. */
+#define SAVE_REGISTERS1() \
+ asm ("movq %rax, _registers"); \
+ asm ("movq %rbx, _registers+8"); \
+ asm ("movq %rcx, _registers+16"); \
+ asm ("movq %rdx, _registers+24"); \
+ asm ("movq %rsi, _registers+32"); \
+ asm ("movq %rdi, _registers+40"); \
+ asm ("movq %rbp, _registers+48"); \
+ asm ("movq %r8, _registers+64"); \
+ asm ("movq %r9, _registers+72"); \
+ asm ("movq %r10, _registers+80"); \
+ asm ("movq %r11, _registers+88"); \
+ asm ("movq %r12, _registers+96"); \
+ asm ("movq %r13, _registers+104"); \
+ asm ("movq %r14, _registers+112"); \
+ asm ("movq %r15, _registers+120"); \
+ asm ("movw $0, %ax"); \
+ asm ("movw %ds, _segregisters+12"); \
+ asm ("movw %ax, _segregisters+14"); \
+ asm ("movw %es, _segregisters+16"); \
+ asm ("movw %ax, _segregisters+18"); \
+ asm ("movw %fs, _segregisters+20"); \
+ asm ("movw %ax, _segregisters+22"); \
+ asm ("movw %gs, _segregisters+24"); \
+ asm ("movw %ax, _segregisters+26")
+#define SAVE_ERRCODE() \
+ asm ("popq %rbx"); \
+ asm ("movq %rbx, _gdb_errcode")
+#define SAVE_REGISTERS2() \
+ asm ("popq %rbx"); /* old rip */ \
+ asm ("movq %rbx, _registers+128"); \
+ asm ("popq %rbx"); /* old cs */ \
+ asm ("movl %ebx, _segregisters+4"); \
+ asm ("popq %rbx"); /* old rflags */ \
+ asm ("movl %ebx, _segregisters"); \
+ /* Now that we've done the pops, we can save the stack pointer." */ \
+ asm ("movw %ss, _segregisters+8"); \
+ asm ("movw %ax, _segregisters+10"); \
+ asm ("movq %rsp, _registers+56")
+
+/* See if _mem_fault_routine is set, if so just iretq to that address. */
+#define CHECK_FAULT() \
+ asm ("cmpq $0, _mem_fault_routine"); \
+ asm ("jne mem_fault")
+
+asm (".text");
+asm ("mem_fault:");
+ /* OK to clobber temp _registers; we're just going to end up in set_mem_err. */
+ /* Pop error code from the stack and save it. */
+ asm ("popq %rax");
+ asm ("movq %rax, _gdb_errcode");
+
+ asm ("popq %rax"); /* rip */
+ /* We don't want to return there, we want to return to the function
+ pointed to by _mem_fault_routine instead. */
+ asm ("movq _mem_fault_routine, %rax");
+ asm ("popq %rcx"); /* cs (low 16 bits; junk in hi 16 bits). */
+ asm ("popq %rdx"); /* rflags */
+
+ /* Remove this stack frame; when we do the iretq, we will be going to
+ the start of a function, so we want the stack to look just like it
+ would after a "call" instruction. */
+ asm ("leave");
+
+ /* Push the stuff that iretq wants. */
+ asm ("pushq %rdx"); /* rflags */
+ asm ("pushq %rcx"); /* cs */
+ asm ("pushq %rax"); /* rip */
+
+ /* Zero _mem_fault_routine. */
+ asm ("movq $0, %rax");
+ asm ("movq %rax, _mem_fault_routine");
+
+ asm ("iretq");
+
+#define CALL_HOOK() asm("call _remcomHandler")
+
+/* These functions are called when an exception occurs. It saves
+ * all the cpu regs in the _registers array, munges the stack a bit,
+ * and invokes an exception handler (remcom_handler).
+ *
+ * stack on entry: stack on exit:
+ * old rflags vector number
+ * old cs (zero-filled to 64 bits)
+ * old rip
+ *
+ */
+extern void
+_catchException3 (void);
+asm(".text");
+asm(".globl _catchException3");
+asm("_catchException3:");
+ SAVE_REGISTERS1();
+ SAVE_REGISTERS2();
+ asm ("pushq $3");
+ CALL_HOOK();
+
+/* Same thing for exception 1. */
+extern void
+_catchException1 (void);
+asm(".text");
+asm(".globl _catchException1");
+asm("_catchException1:");
+ SAVE_REGISTERS1();
+ SAVE_REGISTERS2();
+ asm ("pushq $1");
+ CALL_HOOK();
+
+/* Same thing for exception 0. */
+extern void
+_catchException0 (void);
+asm(".text");
+asm(".globl _catchException0");
+asm("_catchException0:");
+ SAVE_REGISTERS1();
+ SAVE_REGISTERS2();
+ asm ("pushq $0");
+ CALL_HOOK();
+
+/* Same thing for exception 4. */
+extern void
+_catchException4 (void);
+asm(".text");
+asm(".globl _catchException4");
+asm("_catchException4:");
+ SAVE_REGISTERS1();
+ SAVE_REGISTERS2();
+ asm ("pushq $4");
+ CALL_HOOK();
+
+/* Same thing for exception 5. */
+extern void
+_catchException5 (void);
+asm(".text");
+asm(".globl _catchException5");
+asm("_catchException5:");
+ SAVE_REGISTERS1();
+ SAVE_REGISTERS2();
+ asm ("pushq $5");
+ CALL_HOOK();
+
+/* Same thing for exception 6. */
+extern void
+_catchException6 (void);
+asm(".text");
+asm(".globl _catchException6");
+asm("_catchException6:");
+ SAVE_REGISTERS1();
+ SAVE_REGISTERS2();
+ asm ("pushq $6");
+ CALL_HOOK();
+
+/* Same thing for exception 7. */
+extern void
+_catchException7 (void);
+asm(".text");
+asm(".globl _catchException7");
+asm("_catchException7:");
+ SAVE_REGISTERS1();
+ SAVE_REGISTERS2();
+ asm ("pushq $7");
+ CALL_HOOK();
+
+/* Same thing for exception 8. */
+extern void
+_catchException8 (void);
+asm(".text");
+asm(".globl _catchException8");
+asm("_catchException8:");
+ SAVE_REGISTERS1();
+ SAVE_ERRCODE();
+ SAVE_REGISTERS2();
+ asm ("pushq $8");
+ CALL_HOOK();
+
+/* Same thing for exception 9. */
+extern void
+_catchException9 (void);
+asm(".text");
+asm(".globl _catchException9");
+asm("_catchException9:");
+ SAVE_REGISTERS1();
+ SAVE_REGISTERS2();
+ asm ("pushq $9");
+ CALL_HOOK();
+
+/* Same thing for exception 10. */
+extern void
+_catchException10 (void);
+asm(".text");
+asm(".globl _catchException10");
+asm("_catchException10:");
+ SAVE_REGISTERS1();
+ SAVE_ERRCODE();
+ SAVE_REGISTERS2();
+ asm ("pushq $10");
+ CALL_HOOK();
+
+/* Same thing for exception 12. */
+extern void
+_catchException12 (void);
+asm(".text");
+asm(".globl _catchException12");
+asm("_catchException12:");
+ SAVE_REGISTERS1();
+ SAVE_ERRCODE();
+ SAVE_REGISTERS2();
+ asm ("pushq $12");
+ CALL_HOOK();
+
+/* Same thing for exception 16. */
+extern void
+_catchException16 (void);
+asm(".text");
+asm(".globl _catchException16");
+asm("_catchException16:");
+ SAVE_REGISTERS1();
+ SAVE_REGISTERS2();
+ asm ("pushq $16");
+ CALL_HOOK();
+
+/* For 13, 11, and 14 we have to deal with the CHECK_FAULT stuff. */
+
+/* Same thing for exception 13. */
+extern void
+_catchException13 (void);
+asm (".text");
+asm (".globl _catchException13");
+asm ("_catchException13:");
+ CHECK_FAULT();
+ SAVE_REGISTERS1();
+ SAVE_ERRCODE();
+ SAVE_REGISTERS2();
+ asm ("pushq $13");
+ CALL_HOOK();
+
+/* Same thing for exception 11. */
+extern void
+_catchException11 (void);
+asm (".text");
+asm (".globl _catchException11");
+asm ("_catchException11:");
+ CHECK_FAULT();
+ SAVE_REGISTERS1();
+ SAVE_ERRCODE();
+ SAVE_REGISTERS2();
+ asm ("pushq $11");
+ CALL_HOOK();
+
+/* Same thing for exception 14. */
+extern void
+_catchException14 (void);
+asm (".text");
+asm (".globl _catchException14");
+asm ("_catchException14:");
+ CHECK_FAULT();
+ SAVE_REGISTERS1();
+ SAVE_ERRCODE();
+ SAVE_REGISTERS2();
+ asm ("pushq $14");
+ CALL_HOOK();
+
+/*
+ * remcomHandler is a front end for _handle_exception. It moves the
+ * stack pointer into an area reserved for debugger use.
+ */
+asm("_remcomHandler:");
+ asm("popq %rax"); /* pop off return address */
+ asm("popq %rdi"); /* get the exception number in %rdi to pass it as the first argument to _handle_exception */
+ asm("movq _stackPtr, %rsp"); /* move to remcom stack area */
+ asm("call _handle_exception"); /* this never returns */
+
+void
+_returnFromException ()
+{
+ _return_to_prog ();
+}
+
+void
+debug_error (format, parm)
+ char *format;
+ char *parm;
+{
+ printf (format, parm);
+}
+
+int
+hex (ch)
+ char ch;
+{
+ if ((ch >= 'a') && (ch <= 'f'))
+ return (ch - 'a' + 10);
+ if ((ch >= '0') && (ch <= '9'))
+ return (ch - '0');
+ if ((ch >= 'A') && (ch <= 'F'))
+ return (ch - 'A' + 10);
+ return (-1);
+}
+
+static char remcomInBuffer[BUFMAX];
+static char remcomOutBuffer[BUFMAX];
+
+/* scan for the sequence $ #<checksum> */
+
+char *
+getpacket (void)
+{
+ char *buffer = &remcomInBuffer[0];
+ unsigned char checksum;
+ unsigned char xmitcsum;
+ int count;
+ char ch;
+
+ while (1)
+ {
+ /* wait around for the start character, ignore all other characters */
+ while ((ch = getDebugChar ()) != '$')
+ ;
+
+ retry:
+ checksum = 0;
+ xmitcsum = -1;
+ count = 0;
+
+ /* now, read until a # or end of buffer is found */
+ while (count < BUFMAX)
+ {
+ ch = getDebugChar ();
+ if (ch == '$')
+ goto retry;
+ if (ch == '#')
+ break;
+ checksum = checksum + ch;
+ buffer[count] = ch;
+ count = count + 1;
+ }
+ buffer[count] = 0;
+
+ if (ch == '#')
+ {
+ ch = getDebugChar ();
+ xmitcsum = hex (ch) << 4;
+ ch = getDebugChar ();
+ xmitcsum += hex (ch);
+
+ if (checksum != xmitcsum)
+ {
+ debug_error ("failed checksum");
+ putDebugChar ('-'); /* failed checksum */
+ }
+ else
+ {
+ putDebugChar ('+'); /* successful transfer */
+
+ /* if a sequence char is present, reply the sequence ID */
+ if (buffer[2] == ':')
+ {
+ putDebugChar (buffer[0]);
+ putDebugChar (buffer[1]);
+
+ return &buffer[3];
+ }
+
+ return &buffer[0];
+ }
+ }
+ }
+}
+
+/* send the packet in buffer. */
+
+void
+putpacket (char *buffer)
+{
+ unsigned char checksum;
+ int count;
+ char ch;
+
+ /* $<packet info>#<checksum>. */
+ do
+ {
+ putDebugChar ('$');
+ checksum = 0;
+ count = strlen (buffer);
+
+ count = gdb_run_length_encode (buffer, count);
+ buffer[count] = '\0';
+ count = 0;
+
+ while ((ch = buffer[count]))
+ {
+ putDebugChar (ch);
+ checksum += ch;
+ count += 1;
+ }
+
+ putDebugChar ('#');
+ putDebugChar (hexchars[checksum >> 4]);
+ putDebugChar (hexchars[checksum & 0x0f]);
+
+ }
+ while (getDebugChar () != '+');
+}
+
+/* Address of a routine to RTE to if we get a memory fault. */
+static void (*volatile _mem_fault_routine) () = NULL;
+
+/* Indicate to caller of mem2hex or hex2mem that there has been an
+ error. */
+static volatile int mem_err = 0;
+
+void
+set_mem_err (void)
+{
+ mem_err = 1;
+}
+
+/* These are separate functions so that they are so short and sweet
+ that the compiler won't save any _registers (if there is a fault
+ to mem_fault, they won't get restored, so there better not be any
+ saved). */
+int
+get_char (char *addr)
+{
+ return *addr;
+}
+
+void
+set_char (char *addr, int val)
+{
+ *addr = val;
+}
+
+/* convert the memory pointed to by mem into hex, placing result in buf */
+/* return a pointer to the last char put in buf (null) */
+/* If MAY_FAULT is non-zero, then we should set mem_err in response to
+ a fault; if zero treat a fault like any other fault in the stub. */
+char *
+mem2hex (char *mem, char * buf, uint32_t count, uint32_t may_fault)
+{
+ int i;
+ unsigned char ch;
+
+ if (may_fault) {
+ _mem_fault_routine = set_mem_err;
+ }
+
+ for (i = 0; i < count; i++)
+ {
+ ch = get_char (mem++);
+ if (may_fault && mem_err) {
+ return (buf);
+ }
+ *buf++ = hexchars[ch >> 4];
+ *buf++ = hexchars[ch & 0x0f];
+ }
+ *buf = 0;
+
+ if (may_fault) {
+ _mem_fault_routine = NULL;
+ }
+
+ return (buf);
+}
+
+/* convert the hex array pointed to by buf into binary to be placed in mem */
+/* return a pointer to the character AFTER the last byte written */
+char *
+hex2mem (char *buf, char *mem, uint32_t count, uint32_t may_fault)
+{
+ int i;
+ unsigned char ch;
+
+ if (may_fault)
+ _mem_fault_routine = set_mem_err;
+ for (i = 0; i < count; i++)
+ {
+ ch = hex (*buf++) << 4;
+ ch = ch + hex (*buf++);
+ set_char (mem++, ch);
+ if (may_fault && mem_err)
+ return (mem);
+ }
+ if (may_fault)
+ _mem_fault_routine = NULL;
+ return (mem);
+}
+
+/* this function takes the x64 exception vector and attempts to
+ translate this number into a unix compatible signal value */
+uint32_t
+computeSignal (uint64_t exceptionVector)
+{
+ uint32_t sigval;
+ switch (exceptionVector)
+ {
+ case 0:
+ sigval = 8;
+ break; /* divide by zero */
+ case 1:
+ sigval = 5;
+ break; /* debug exception */
+ case 3:
+ sigval = 5;
+ break; /* breakpoint */
+ case 4:
+ sigval = 16;
+ break; /* into instruction (overflow) */
+ case 5:
+ sigval = 16;
+ break; /* bound instruction */
+ case 6:
+ sigval = 4;
+ break; /* Invalid opcode */
+ case 7:
+ sigval = 8;
+ break; /* coprocessor not available */
+ case 8:
+ sigval = 7;
+ break; /* double fault */
+ case 9:
+ sigval = 11;
+ break; /* coprocessor segment overrun */
+ case 10:
+ sigval = 11;
+ break; /* Invalid TSS */
+ case 11:
+ sigval = 11;
+ break; /* Segment not present */
+ case 12:
+ sigval = 11;
+ break; /* stack exception */
+ case 13:
+ sigval = 11;
+ break; /* general protection */
+ case 14:
+ sigval = 11;
+ break; /* page fault */
+ case 16:
+ sigval = 7;
+ break; /* coprocessor error */
+ default:
+ sigval = 7; /* "software generated" */
+ }
+ return (sigval);
+}
+
+/**********************************************/
+/* WHILE WE FIND NICE HEX CHARS, BUILD AN INT */
+/* RETURN NUMBER OF CHARS PROCESSED */
+/**********************************************/
+uint32_t
+hexToInt (char **ptr, int64_t *intValue)
+{
+ uint32_t numChars = 0;
+ int hexValue;
+
+ *intValue = 0;
+
+ while (**ptr)
+ {
+ hexValue = hex (**ptr);
+ if (hexValue >= 0)
+ {
+ *intValue = (*intValue << 4) | hexValue;
+ numChars++;
+ }
+ else
+ break;
+
+ (*ptr)++;
+ }
+
+ return (numChars);
+}
+
+/*
+ * This function does all command procesing for interfacing to gdb.
+ */
+void
+_handle_exception (uint64_t exceptionVector)
+{
+ uint32_t sigval, stepping;
+ int64_t addr, length;
+ char *ptr;
+
+ gdb_vector = exceptionVector;
+
+ /* reply to host that an exception has occurred */
+ sigval = computeSignal (exceptionVector);
+
+ ptr = remcomOutBuffer;
+
+ *ptr++ = 'T'; /* notify gdb with signo, RIP, and thread id */
+ *ptr++ = hexchars[sigval >> 4];
+ *ptr++ = hexchars[sigval & 0x0f];
+
+ *ptr++ = hexchars[RIP >> 4];
+ *ptr++ = hexchars[RIP & 0x0f];
+ *ptr++ = ':';
+ ptr = mem2hex ((char *)&_registers[RIP], ptr, 8, 0); /* RIP */
+ *ptr++ = ';';
+
+ gdb_strcpy (ptr, "thread:"THREAD_TID";");
+
+ putpacket (remcomOutBuffer);
+
+ stepping = 0;
+
+ while (1 == 1)
+ {
+ remcomOutBuffer[0] = 0;
+ ptr = getpacket ();
+
+ switch (*ptr++)
+ {
+ case '?':
+ remcomOutBuffer[0] = 'S';
+ remcomOutBuffer[1] = hexchars[sigval >> 4];
+ remcomOutBuffer[2] = hexchars[sigval & 0x0f];
+ remcomOutBuffer[3] = 0;
+ break;
+ case 'D': /* detach */
+ gdb_strcpy (remcomOutBuffer, "OK");
+ break;
+ case 'g': /* return the value of the CPU _registers */
+ ptr = mem2hex ((char *) _registers, remcomOutBuffer, NUMREGBYTES, 0);
+ mem2hex ((char *) _segregisters, ptr, NUMSEGREGBYTES, 0);
+ break;
+ case 'G': /* set the value of the CPU _registers - return OK */
+ hex2mem (ptr, (char *) _registers, NUMREGBYTES, 0);
+ ptr += (NUMREGBYTES * 2);
+ hex2mem (ptr, (char *) _segregisters, NUMSEGREGBYTES, 0);
+ gdb_strcpy (remcomOutBuffer, "OK");
+ break;
+ case 'p': /* return the value of a single CPU register */
+ {
+ int64_t regno;
+
+ if (hexToInt (&ptr, &regno)) {
+ if (regno >= 0) {
+ if (regno < NUMREGS) {
+ mem2hex ((char *) &_registers[regno], remcomOutBuffer, 8, 0);
+ break;
+ } else if (regno < (NUMREGS + NUMSEGREGS)) {
+ mem2hex ((char *) &_segregisters[regno - NUMREGS], remcomOutBuffer, 4, 0);
+ break;
+ }
+ }
+ }
+
+ gdb_strcpy (remcomOutBuffer, "E01");
+ break;
+ }
+ case 'P': /* set the value of a single CPU register - return OK */
+ {
+ int64_t regno;
+
+ if (hexToInt (&ptr, &regno) && *ptr++ == '=') {
+ if (regno >= 0) {
+ if (regno < NUMREGS) {
+ hex2mem (ptr, (char *) &_registers[regno], 8, 0);
+ gdb_strcpy (remcomOutBuffer, "OK");
+ break;
+ } else if (regno < (NUMREGS + NUMSEGREGS)) {
+ hex2mem (ptr, (char *) &_segregisters[regno], 4, 0);
+ gdb_strcpy (remcomOutBuffer, "OK");
+ break;
+ } else {
+ /*
+ * Hack to deal with gdb client asking to set weird registers
+ * such as "orig_rax" - lie and say we set the non-existent register.
+ */
+ gdb_strcpy (remcomOutBuffer, "OK");
+ break;
+ }
+ }
+ }
+ gdb_strcpy (remcomOutBuffer, "E01");
+ break;
+ }
+ /* mAA..AA,LLLL Read LLLL bytes at address AA..AA */
+ case 'm':
+ /* TRY TO READ %x,%x. IF SUCCEED, SET PTR = 0 */
+ if (hexToInt (&ptr, &addr))
+ if (*(ptr++) == ',')
+ if (hexToInt (&ptr, &length))
+ {
+ ptr = 0;
+ mem_err = 0;
+ mem2hex ((char *) addr, remcomOutBuffer, length, 1);
+ if (mem_err)
+ {
+ gdb_strcpy (remcomOutBuffer, "E03");
+ debug_error ("memory fault");
+ }
+ }
+
+ if (ptr)
+ {
+ gdb_strcpy (remcomOutBuffer, "E01");
+ }
+ break;
+
+ /* MAA..AA,LLLL: Write LLLL bytes at address AA.AA return OK */
+ case 'M':
+ /* TRY TO READ '%x,%x:'. IF SUCCEED, SET PTR = 0 */
+ if (hexToInt (&ptr, &addr))
+ if (*(ptr++) == ',')
+ if (hexToInt (&ptr, &length))
+ if (*(ptr++) == ':')
+ {
+ mem_err = 0;
+ hex2mem (ptr, (char *) addr, length, 1);
+
+ if (mem_err)
+ {
+ gdb_strcpy (remcomOutBuffer, "E03");
+ debug_error ("memory fault");
+ }
+ else
+ {
+ gdb_strcpy (remcomOutBuffer, "OK");
+ }
+
+ ptr = 0;
+ }
+ if (ptr)
+ {
+ gdb_strcpy (remcomOutBuffer, "E02");
+ }
+ break;
+
+ /* cAA..AA Continue at address AA..AA(optional) */
+ /* sAA..AA Step one instruction from AA..AA(optional) */
+ case 's':
+ stepping = 1;
+ /* FALLTHROUGH */
+ case 'c':
+ /* try to read optional parameter,RIP unchanged if no parm */
+ if (hexToInt (&ptr, &addr)) {
+ _registers[RIP] = addr;
+ }
+
+ /* clear the trace bit */
+ _segregisters[PS] &= 0xfffffeff;
+
+ /* set the trace bit if we're stepping */
+ if (stepping) {
+ _segregisters[PS] |= 0x00000100;
+ }
+
+ _returnFromException (); /* this is a jump */
+ break;
+
+ /* kill the program */
+ case 'k':
+ /*
+ * We don't actually want to reboot the loader - do nothing.
+ */
+ break;
+
+ /* Set thread for subsequent operations; ignore this since we are a single threaded target */
+ case 'H':
+ gdb_strcpy (remcomOutBuffer, "OK");
+ break;
+
+ /*
+ * General Query Packets
+ *
+ * See - https://sourceware.org/gdb/current/onlinedocs/gdb/General-Query-Packets.html
+ */
+ case 'q':
+ /* qSupported packet */
+ if (gdb_str_starts_with(ptr, "Supported")) {
+ gdb_strcpy (remcomOutBuffer, "multiprocess-;vContSupported-;QThreadEvents-");
+ }
+ /* qC packet */
+ else if (strcmp(ptr, "C") == 0) {
+ // single threaded target - reply with thread id
+ gdb_strcpy (remcomOutBuffer, "QC"THREAD_TID);
+ }
+ /* qTStatus packet */
+ else if (strcmp (ptr, "TStatus") == 0) {
+ // no trace is running
+ gdb_strcpy (remcomOutBuffer, "T0");
+ }
+ break;
+ } /* switch */
+
+ /* reply to the request */
+ putpacket (remcomOutBuffer);
+ }
+}
+
+/* this function is used to set up exception handlers for tracing and
+ breakpoints */
+void
+set_debug_traps (void)
+{
+ _stackPtr = &remcomStack[STACKSIZE / sizeof (uint64_t) - 1];
+
+ printf("Setting Debug Traps for GDB.\n\n");
+
+ exceptionHandler (0, _catchException0);
+ exceptionHandler (1, _catchException1);
+ exceptionHandler (3, _catchException3);
+ exceptionHandler (4, _catchException4);
+ exceptionHandler (5, _catchException5);
+ exceptionHandler (6, _catchException6);
+ exceptionHandler (7, _catchException7);
+ exceptionHandler (8, _catchException8);
+ exceptionHandler (9, _catchException9);
+ exceptionHandler (10, _catchException10);
+ exceptionHandler (11, _catchException11);
+ exceptionHandler (12, _catchException12);
+ /*
+ * Don't install GP exception handler
+ */
+ // exceptionHandler (13, _catchException13);
+ exceptionHandler (14, _catchException14);
+ exceptionHandler (16, _catchException16);
+}
+
+
+void
+gdb_init (void)
+{
+ if (!initialized) {
+ set_debug_traps ();
+ }
+ initialized = 1;
+}
+
+/* This function will generate a breakpoint exception. It is used at the
+ beginning of a program to sync up with a debugger and can be used
+ otherwise as a quick means to stop program execution and "break" into
+ the debugger. */
+
+void
+breakpoint (void)
+{
+ if (!initialized) {
+ gdb_init ();
+ }
+
+ BREAKPOINT ();
+}
+
+static void
+gdb_bcopy (void *from, void *to, int length)
+{
+ char *fp = from;
+ char *tp = to;
+
+ while (length--) *tp++ = *fp++;
+}
+
+#define GDB_RLE_LEN_ENCODE_OFFSET 29
+#define GDB_RLE_MIN_ENCODE_LEN 4
+#define GDB_RLE_MAX_ENCODE_LEN (126 - GDB_RLE_LEN_ENCODE_OFFSET)
+
+static size_t
+gdb_run_length_encode (char *buffer, size_t length)
+{
+ if (length < GDB_RLE_MIN_ENCODE_LEN)
+ return length;
+
+ size_t newLen = length;
+ char *rleStart = &buffer[0];
+ int i;
+
+ for (i = 1; i < newLen; ++i) {
+ // rleBlockLen is the count of identical characters in the block.
+ // The encoding is <char>*<repeat> where repeat is the number of times to repeat
+ // <char>, therefore <repeat> is (rleBlockLen - 1)
+ char rleBlockLen = (&buffer[i] - rleStart) + 1;
+
+ if ((i == (newLen - 1)) || (buffer[i] != *rleStart) || ((rleBlockLen - 1) == GDB_RLE_MAX_ENCODE_LEN)) {
+ // reached an end condition
+ if (buffer[i] != *rleStart) {
+ // in this case buffer[i] is pointing at the first non encodable byte after the block
+ // so adjust rleBlockLen
+ rleBlockLen -= 1;
+ }
+
+ if (rleBlockLen < GDB_RLE_MIN_ENCODE_LEN) {
+ rleStart = &buffer[i];
+ continue;
+ }
+
+ char encodedLength = GDB_RLE_LEN_ENCODE_OFFSET + (rleBlockLen - 1);
+ if ((encodedLength == '+') || (encodedLength == '-') ||
+ (encodedLength == '$') || (encodedLength == '#')) {
+ // don't rle if encoded length is a reserved character
+ // TBD: could still encode by encoding a shorter block, but for now just leave it unencoded
+ rleStart = &buffer[i];
+ continue;
+ }
+
+ // only encode if the encoded length is not a reserved character
+ rleStart[1] = '*';
+ rleStart[2] = encodedLength;
+ if (&rleStart[3] < &buffer[newLen]) {
+ // if there is more data in the buffer, shift it left up to the end of the newly
+ // encoded data
+ size_t numBytesToRemove = rleBlockLen - 3;
+ char *firstByteToRemove = &rleStart[3];
+ char *firstByteToMove = firstByteToRemove + numBytesToRemove;
+ int numBytesToMove = newLen - (firstByteToRemove - buffer) - numBytesToRemove;
+ if (numBytesToMove > 0) {
+ gdb_bcopy(firstByteToMove, firstByteToRemove, numBytesToMove);
+ }
+ newLen -= numBytesToRemove;
+ // adjust i so that processing will continue on the moved data
+ i = (&rleStart[3] - buffer);
+ }
+ rleStart = &buffer[i];
+ }
+ }
+
+ return newLen;
+}
+
+static char *
+gdb_strcpy (char *dest,const char *src)
+{
+ char *ptr = dest;
+
+ while (*src) *ptr++ = *src++;
+ *ptr = '\0';
+
+ return dest;
+}
+
+/* return 1 if str starts with prefix and 0 otherwise */
+static int
+gdb_str_starts_with (char *str, char *prefix)
+{
+ return (strncmp (str, prefix, strlen (prefix)) == 0);
+}
+
+
+// Default Implementations of OS Specific Functions
+
+#ifdef GDB_USE_SERIAL_PORT_IO
+
+// Implementations of I/O functions - putDebugChar() and getDebugChar()
+
+#define DEBUG_COM_PORT ((volatile unsigned short)0x3f8)
+#define COM_REG_THB (DEBUG_COM_PORT + 0)
+#define COM_REG_RB (DEBUG_COM_PORT + 0)
+
+#define COM_REG_LSR (DEBUG_COM_PORT + 5)
+#define LSR_THB_EMPTY (1<<5)
+#define LSR_RB_READY (1<<0)
+
+extern void phys_write8 (uint64_t port, uint8_t data);
+extern uint8_t phys_read8 (uint64_t port);
+
+void
+putDebugChar (char c)
+{
+ while(! (phys_read8(COM_REG_LSR) & LSR_THB_EMPTY) ) {
+ // wait for current byte to be written
+ }
+ phys_write8 (COM_REG_THB, c);
+}
+
+int
+getDebugChar (void)
+{
+ char c;
+ while (! (phys_read8 (COM_REG_LSR) & LSR_RB_READY) ) {
+ // wait for a character
+ }
+ c = phys_read8 (COM_REG_RB);
+ return c;
+}
+
+#endif /* GDB_USE_SERIAL_PORT_IO */
+
+#ifdef GDB_USE_STD_X64_EXCEPTION_HANDLER
+
+// Implementation of Interrupt Descriptor Table (IDT) function - exceptionHandler()
+
+typedef struct idtr_table_entry {
+ uint16_t handler_addr_offset1;
+ uint16_t segment_selector;
+ uint16_t flags;
+ uint16_t handler_addr_offset2;
+ uint32_t handler_addr_offset3;
+ uint32_t reserved;
+} __attribute__((packed)) idtr_table_entry_t;
+
+typedef struct idtr_table_addr {
+ uint16_t limit; // the offset (in bytes) of the last valid byte in the idtr
+ idtr_table_entry_t *addr; // the base address of the idtr in memory
+} __attribute__((packed)) idtr_table_addr_t;
+
+/* store the address of the interrupt descrtiptor table in memory */
+void store_idtr (idtr_table_addr_t *idtr_table_addr);
+
+asm(".text");
+asm("store_idtr:");
+ // %rdi is the parameter to this function
+ // a pointer to a 10-byte memory location
+ asm("sidt (%rdi)");
+ asm("retq");
+
+/* return the value of the 16-bit %cs (code segment) register */
+uint16_t get_cs_reg (void);
+
+asm(".text");
+asm("get_cs_reg:");
+ asm("xor %rax, %rax");
+ asm("mov %cs, %rax");
+ asm("retq");
+
+void
+exceptionHandler (int intr_vector, void *intr_handler)
+{
+ idtr_table_addr_t idtr_table_addr;
+ store_idtr (&idtr_table_addr);
+
+ idtr_table_entry_t *idtr_entry = &idtr_table_addr.addr[intr_vector];
+ idtr_entry->segment_selector = get_cs_reg ();
+
+ uint64_t intr_handler_addr = (uint64_t)intr_handler;
+ idtr_entry->handler_addr_offset1 = (uint16_t)intr_handler_addr;
+ idtr_entry->handler_addr_offset2 = (uint16_t)(intr_handler_addr >> 16);
+ idtr_entry->handler_addr_offset3 = (uint32_t)(intr_handler_addr >> 32);
+}
+
+#endif /* GDB_USE_STD_X64_EXCEPTION_HANDLER */
--
2.14.1.windows.1