kgdb patches for 5.2-rc1

Mostly clean ups but there are also a couple of out-of-bounds accesses
 (including a potential write to the byte before a static buffer).
 
 The main changes are:
 
  * Fixes those out-of-bounds access (empty string to configure
    test module could write the byte before a buffer, high cpu counts
    could read outside of per-cpu structures).
 
  * Improvements to string handling problems picked up by new compiler
    warnings and other static checks. Most are fixing benign issues that
    can't be tickled without code changes but still reduce the wtf factor
    a little.
 
  * Tidy up the terminal output.
 
 Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
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Merge tag 'kgdb-5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux

Pull kgdb updates from Daniel Thompson:
 "Mostly cleanups but there are also a couple of fixes for out-of-bounds
  accesses (including a potential write to the byte before a static
  buffer).

  The main changes are:

   - Fixes to those out-of-bounds access (empty string to configure test
     module could write the byte before a buffer, high cpu counts could
     read outside of per-cpu structures).

   - Improvements to string handling problems picked up by new compiler
     warnings and other static checks. Most are fixing benign issues
     that can't be tickled without code changes but still reduce the wtf
     factor a little.

   - Tidy up the terminal output"

* tag 'kgdb-5.2-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux:
  kdb: Fix bound check compiler warning
  kdb: do a sanity check on the cpu in kdb_per_cpu()
  kdb: Get rid of broken attempt to print CCVERSION in kdb summary
  misc: kgdbts: fix out-of-bounds access in function param_set_kgdbts_var
  kdb: kdb_support: replace strcpy() by strscpy()
  gdbstub: Replace strcpy() by strscpy()
  gdbstub: mark expected switch fall-throughs

kernel/debug/gdbstub.c

@@ -1033,13 +1033,14 @@ int gdb_serial_stub(struct kgdb_state *ks)
 				return DBG_PASS_EVENT;
 			}
 #endif
+			/* Fall through */
 		case 'C': /* Exception passing */
 			tmp = gdb_cmd_exception_pass(ks);
 			if (tmp > 0)
 				goto default_handle;
 			if (tmp == 0)
 				break;
-			/* Fall through on tmp < 0 */
+			/* Fall through - on tmp < 0 */
 		case 'c': /* Continue packet */
 		case 's': /* Single step packet */
 			if (kgdb_contthread && kgdb_contthread != current) {
@@ -1048,7 +1049,7 @@ int gdb_serial_stub(struct kgdb_state *ks)
 				break;
 			}
 			dbg_activate_sw_breakpoints();
-			/* Fall through to default processing */
+			/* Fall through - to default processing */
 		default:
 default_handle:
 			error = kgdb_arch_handle_exception(ks->ex_vector,
@@ -1094,10 +1095,10 @@ int gdbstub_state(struct kgdb_state *ks, char *cmd)
 		return error;
 	case 's':
 	case 'c':
-		strcpy(remcom_in_buffer, cmd);
+		strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
 		return 0;
 	case '$':
-		strcpy(remcom_in_buffer, cmd);
+		strscpy(remcom_in_buffer, cmd, sizeof(remcom_in_buffer));
 		gdbstub_use_prev_in_buf = strlen(remcom_in_buffer);
 		gdbstub_prev_in_buf_pos = 0;
 		return 0;

kernel/debug/kdb/Makefile

@@ -6,7 +6,6 @@
 # Copyright (c) 2009 Wind River Systems, Inc. All Rights Reserved.
 #
 
-CCVERSION	:= $(shell $(CC) -v 2>&1 | sed -ne '$$p')
 obj-y := kdb_io.o kdb_main.o kdb_support.o kdb_bt.o gen-kdb_cmds.o kdb_bp.o kdb_debugger.o
 obj-$(CONFIG_KDB_KEYBOARD)    += kdb_keyboard.o
 

kernel/debug/kdb/kdb_io.c

@@ -446,7 +446,7 @@ poll_again:
 char *kdb_getstr(char *buffer, size_t bufsize, const char *prompt)
 {
 	if (prompt && kdb_prompt_str != prompt)
-		strncpy(kdb_prompt_str, prompt, CMD_BUFLEN);
+		strscpy(kdb_prompt_str, prompt, CMD_BUFLEN);
 	kdb_printf(kdb_prompt_str);
 	kdb_nextline = 1;	/* Prompt and input resets line number */
 	return kdb_read(buffer, bufsize);

kernel/debug/kdb/kdb_main.c

@@ -2522,7 +2522,6 @@ static int kdb_summary(int argc, const char **argv)
 	kdb_printf("machine    %s\n", init_uts_ns.name.machine);
 	kdb_printf("nodename   %s\n", init_uts_ns.name.nodename);
 	kdb_printf("domainname %s\n", init_uts_ns.name.domainname);
-	kdb_printf("ccversion  %s\n", __stringify(CCVERSION));
 
 	now = __ktime_get_real_seconds();
 	time64_to_tm(now, 0, &tm);
@@ -2584,7 +2583,7 @@ static int kdb_per_cpu(int argc, const char **argv)
 		diag = kdbgetularg(argv[3], &whichcpu);
 		if (diag)
 			return diag;
-		if (!cpu_online(whichcpu)) {
+		if (whichcpu >= nr_cpu_ids || !cpu_online(whichcpu)) {
 			kdb_printf("cpu %ld is not online\n", whichcpu);
 			return KDB_BADCPUNUM;
 		}

kernel/debug/kdb/kdb_support.c

@@ -192,7 +192,7 @@ int kallsyms_symbol_complete(char *prefix_name, int max_len)
 
 	while ((name = kdb_walk_kallsyms(&pos))) {
 		if (strncmp(name, prefix_name, prefix_len) == 0) {
-			strcpy(ks_namebuf, name);
+			strscpy(ks_namebuf, name, sizeof(ks_namebuf));
 			/* Work out the longest name that matches the prefix */
 			if (++number == 1) {
 				prev_len = min_t(int, max_len-1,