[Qemu-devel] Re: [PATCH] x86_64 debug registers for gdb

[Jan Kiszka]

Jason Wessel wrote:
> This patch fixes the registers for the 'g' and 'G' packets for the
> qemu-system-x86_64 target.  It allows gdb 6.5 to debug a linux kernel
> and get a stack back trace.

Here comes a corrected (RBX and RDX were mixed) and slightly enhanced
(segment register reading, don't know how writing should look like)
version of this patch. Tested successfully with qemu-0.9.0 and gdb-6.6.
Would be nice to see this support in the next qemu release.

Jan


Index: qemu-0.9.0/gdbstub.c
===================================================================
--- qemu-0.9.0.orig/gdbstub.c
+++ qemu-0.9.0/gdbstub.c
@@ -220,9 +220,78 @@ static int put_packet(GDBState *s, char 
     }
     return 0;
 }
+#if defined(TARGET_X86_64)
+/* Defines from GDB register struct numbers */
+#define _RAX   0
+#define _RBX   1
+#define _RCX   2
+#define _RDX   3
+#define _RSI   4
+#define _RDI   5
+#define _RBP   6
+#define _RSP   7
+#define _R8    8
+#define _R15   15
+#define _PC    16
+#define _PS    17
+#define _CS    18
+#define _SS    19
+#define _DS    20
+#define _ES    21
+#define _FS    22
+#define _GS    23
+#define _NREGS 24
 
-#if defined(TARGET_I386)
+static int cpu_gdb_read_registers(CPUState *env, uint8_t *mem_buf)
+{
+    uint64_t *registers = (uint64_t *)mem_buf;
+    int i;
+
+    registers[_RAX] = env->regs[R_EAX];
+    registers[_RBX] = env->regs[R_EBX];
+    registers[_RCX] = env->regs[R_ECX];
+    registers[_RDX] = env->regs[R_EDX];
+    registers[_RSI] = env->regs[R_ESI];
+    registers[_RDI] = env->regs[R_EDI];
+    registers[_RBP] = env->regs[R_EBP];
+    registers[_RSP] = env->regs[R_ESP];
+    for (i = 8; i < 16; i++)
+        registers[i] = env->regs[i];
+    registers[_PC] = env->eip;
+    registers[_PS] = env->eflags;
+    registers[_CS] = env->segs[R_CS].selector;
+    registers[_SS] = env->segs[R_SS].selector;
+    registers[_DS] = env->segs[R_DS].selector;
+    registers[_ES] = env->segs[R_ES].selector;
+    registers[_FS] = env->segs[R_FS].selector;
+    registers[_GS] = env->segs[R_GS].selector;
+
+    for(i = 0; i < _NREGS; i++)
+        tswapl(registers[i]);
+
+    return _NREGS * 8;
+}
+
+static void cpu_gdb_write_registers(CPUState *env, uint8_t *mem_buf, int size)
+{
+    uint32_t *registers = (uint32_t *)mem_buf;
+    int i;
+
+    env->regs[R_EAX] = tswapl(registers[_RAX]);
+    env->regs[R_EBX] = tswapl(registers[_RBX]);
+    env->regs[R_ECX] = tswapl(registers[_RCX]);
+    env->regs[R_EDX] = tswapl(registers[_RDX]);
+    env->regs[R_ESI] = tswapl(registers[_RSI]);
+    env->regs[R_EDI] = tswapl(registers[_RDI]);
+    env->regs[R_EBP] = tswapl(registers[_RBP]);
+    env->regs[R_ESP] = tswapl(registers[_RSP]);
+    for (i = 8; i < 16; i++)
+        env->regs[i] = tswapl(registers[i]);
+    env->eip = tswapl(registers[_PC]);
+    env->eflags = tswapl(registers[_PS]);
+}
 
+#elif defined(TARGET_I386)
 static int cpu_gdb_read_registers(CPUState *env, uint8_t *mem_buf)
 {
     uint32_t *registers = (uint32_t *)mem_buf;

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