Reimplemented the gdb stub support for the 'g' command (read registers):

* Added an arch_debug_gdb_get_registers() interface that is supposed to provide
  the register values in the format expected by gdb and implemented it for x86.
* Reimplemented gdb_regreply() to use that. Also made it buffer overflow safe.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@41880 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/arch/debug.h

@@ -50,6 +50,8 @@ bool arch_is_debug_variable_defined(const char* variableName);
 status_t arch_set_debug_variable(const char* variableName, uint64 value);
 status_t arch_get_debug_variable(const char* variableName, uint64* value);
 
+ssize_t arch_debug_gdb_get_registers(char* buffer, size_t bufferSize);
+
 #ifdef __cplusplus
 }
 #endif

src/system/kernel/arch/arm/arch_debug.cpp

@@ -334,3 +334,9 @@ arch_debug_unset_current_thread(void)
 }
 
 
+ssize_t
+arch_debug_gdb_get_registers(char* buffer, size_t bufferSize)
+{
+	// TODO: Implement!
+	return B_NOT_SUPPORTED;
+}

src/system/kernel/arch/m68k/arch_debug.cpp

@@ -398,6 +398,14 @@ arch_get_debug_variable(const char* variableName, uint64* value)
 }
 
 
+ssize_t
+arch_debug_gdb_get_registers(char* buffer, size_t bufferSize)
+{
+	// TODO: Implement!
+	return B_NOT_SUPPORTED;
+}
+
+
 status_t
 arch_debug_init(kernel_args *args)
 {

src/system/kernel/arch/mipsel/arch_debug.cpp

@@ -99,6 +99,14 @@ arch_get_debug_variable(const char* variableName, uint64* value)
 }
 
 
+ssize_t
+arch_debug_gdb_get_registers(char* buffer, size_t bufferSize)
+{
+	// TODO: Implement!
+	return B_NOT_SUPPORTED;
+}
+
+
 status_t
 arch_debug_init(kernel_args* args)
 {

src/system/kernel/arch/ppc/arch_debug.cpp

@@ -336,6 +336,14 @@ arch_get_debug_variable(const char* variableName, uint64* value)
 }
 
 
+ssize_t
+arch_debug_gdb_get_registers(char* buffer, size_t bufferSize)
+{
+	// TODO: Implement!
+	return B_NOT_SUPPORTED;
+}
+
+
 status_t
 arch_debug_init(kernel_args *args)
 {

src/system/kernel/arch/x86/arch_debug.cpp

@@ -13,6 +13,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+#include <ByteOrder.h>
 #include <TypeConstants.h>
 
 #include <cpu.h>
@@ -1168,6 +1169,58 @@ arch_get_debug_variable(const char* variableName, uint64* value)
 }
 
 
+/*!	Writes the contents of the CPU registers at some fixed outer stack frame or
+	iframe into the given buffer in the format expected by gdb.
+
+	This function is called in response to gdb's 'g' command.
+
+	\param buffer The buffer to write the registers to.
+	\param bufferSize The size of \a buffer in bytes.
+	\return When successful, the number of bytes written to \a buffer, or a
+		negative error code on error.
+*/
+ssize_t
+arch_debug_gdb_get_registers(char* buffer, size_t bufferSize)
+{
+	struct iframe* frame = get_current_iframe(debug_get_debugged_thread());
+	if (frame == NULL)
+		return B_NOT_SUPPORTED;
+
+	// For x86 the register order is:
+	//
+	//    eax, ebx, ecx, edx,
+	//    esp, ebp, esi, edi,
+	//    eip, eflags,
+	//    cs, ss, ds, es
+	//
+	// Note that even though the segment descriptors are actually 16 bits wide,
+	// gdb requires them as 32 bit integers. Note also that for some reason
+	// gdb wants the register dump in *big endian* format.
+	static const int32 kRegisterCount = 14;
+	uint32 registers[kRegisterCount] = {
+		frame->eax, frame->ebx, frame->ecx, frame->edx,
+		frame->esp, frame->ebp, frame->esi, frame->edi,
+		frame->eip, frame->flags,
+		frame->cs, frame->ds, frame->ds, frame->es
+			// assume ss == ds
+	};
+
+	const char* const bufferStart = buffer;
+
+	for (int32 i = 0; i < kRegisterCount; i++) {
+		int result = snprintf(buffer, bufferSize, "%08" B_PRIx32,
+			B_HOST_TO_BENDIAN_INT32(registers[i]));
+		if (result >= (int)bufferSize)
+			return B_BUFFER_OVERFLOW;
+
+		buffer += result;
+		bufferSize -= result;
+	}
+
+	return buffer - bufferStart;
+}
+
+
 status_t
 arch_debug_init(kernel_args *args)
 {

src/system/kernel/debug/gdb.cpp

@@ -16,6 +16,7 @@
 
 #include <ByteOrder.h>
 
+#include <arch/debug.h>
 #include <arch/debug_console.h>
 #include <debug.h>
 #include <elf.h>
@@ -107,23 +108,34 @@ gdb_reply(char const* format, ...)
 
 
 static void
-gdb_regreply(int const* regs, int numregs)
+gdb_regreply()
 {
-	int i;
-	int len;
-	int sum;
-
 	sReply[0] = '$';
-	for (i = 0; i < numregs; i++)
-		sprintf(sReply + 1 + 8 * i, "%08lx", B_HOST_TO_BENDIAN_INT32(regs[i]));
 
-	len = strlen(sReply);
-	sum = 0;
-	for (i = 1; i < len; i++)
+	// get registers (architecture specific)
+	ssize_t bytesWritten = arch_debug_gdb_get_registers(sReply + 1,
+		sizeof(sReply) - 1);
+	if (bytesWritten < 0) {
+		gdb_reply("E01");
+		return;
+	}
+
+	// add 1 for the leading '$'
+	bytesWritten++;
+
+	// compute check sum
+	int sum = 0;
+	for (int32 i = 1; i < bytesWritten; i++)
 		sum += sReply[i];
 	sum %= 256;
 
-	sprintf(sReply + len, "#%02x", sum);
+	// print check sum
+	int result = snprintf(sReply + bytesWritten, sizeof(sReply) - bytesWritten,
+		"#%02x", sum);
+	if (result >= (ssize_t)sizeof(sReply) - bytesWritten) {
+		gdb_reply("E01");
+		return;
+	}
 
 	gdb_resend_reply();
 }
@@ -227,34 +239,8 @@ gdb_parse_command(void)
 			return QUIT;
 
 		case 'g':
-		{
-#if 0
-			int cpu;
-
-			// command 'g' is used for reading the register
-			// file. Faked by now.
-			//
-			// For x86 the register order is:
-			//
-			//    eax, ebx, ecx, edx,
-			//    esp, ebp, esi, edi,
-			//    eip, eflags,
-			//    cs, ss, ds, es
-			//
-			// Note that even thought the segment descriptors
-			// are actually 16 bits wide, gdb requires them
-			// as 32 bit integers. Note also that for some
-			// reason (unknown to me) gdb wants the register
-			// dump in *big endian* format.
-			cpu = smp_get_current_cpu();
-			gdb_regreply(dbg_register_file[cpu], 14);
-#else
-			(void)gdb_regreply;
-			gdb_reply("E01");
-#endif
-
+			gdb_regreply();
 			break;
-		}
 
 		case 'G':
 			// write registers