kdb: Categorize kdb commands (similar to SysRq categorization)

This patch introduces several new flags to collect kdb commands into
groups (later allowing them to be optionally disabled).

This follows similar prior art to enable/disable magic sysrq
commands.

The commands have been categorized as follows:

Always on:  go (w/o args), env, set, help, ?, cpu (w/o args), sr,
            dmesg, disable_nmi, defcmd, summary, grephelp
Mem read:   md, mdr, mdp, mds, ef, bt (with args), per_cpu
Mem write:  mm
Reg read:   rd
Reg write:  go (with args), rm
Inspect:    bt (w/o args), btp, bta, btc, btt, ps, pid, lsmod
Flow ctrl:  bp, bl, bph, bc, be, bd, ss
Signal:     kill
Reboot:     reboot
All:        cpu, kgdb, (and all of the above), nmi_console

Signed-off-by: Daniel Thompson <[email protected]>
Cc: Jason Wessel <[email protected]>
Signed-off-by: Jason Wessel <[email protected]>

include/linux/kdb.h

@@ -13,9 +13,53 @@
  * Copyright (C) 2009 Jason Wessel <[email protected]>
  */
 
+/* Shifted versions of the command enable bits are be used if the command
+ * has no arguments (see kdb_check_flags). This allows commands, such as
+ * go, to have different permissions depending upon whether it is called
+ * with an argument.
+ */
+#define KDB_ENABLE_NO_ARGS_SHIFT 10
+
 typedef enum {
-	KDB_REPEAT_NO_ARGS	= 0x1, /* Repeat the command w/o arguments */
-	KDB_REPEAT_WITH_ARGS	= 0x2, /* Repeat the command w/ its arguments */
+	KDB_ENABLE_ALL = (1 << 0), /* Enable everything */
+	KDB_ENABLE_MEM_READ = (1 << 1),
+	KDB_ENABLE_MEM_WRITE = (1 << 2),
+	KDB_ENABLE_REG_READ = (1 << 3),
+	KDB_ENABLE_REG_WRITE = (1 << 4),
+	KDB_ENABLE_INSPECT = (1 << 5),
+	KDB_ENABLE_FLOW_CTRL = (1 << 6),
+	KDB_ENABLE_SIGNAL = (1 << 7),
+	KDB_ENABLE_REBOOT = (1 << 8),
+	/* User exposed values stop here, all remaining flags are
+	 * exclusively used to describe a commands behaviour.
+	 */
+
+	KDB_ENABLE_ALWAYS_SAFE = (1 << 9),
+	KDB_ENABLE_MASK = (1 << KDB_ENABLE_NO_ARGS_SHIFT) - 1,
+
+	KDB_ENABLE_ALL_NO_ARGS = KDB_ENABLE_ALL << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_MEM_READ_NO_ARGS = KDB_ENABLE_MEM_READ
+				      << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_MEM_WRITE_NO_ARGS = KDB_ENABLE_MEM_WRITE
+				       << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_REG_READ_NO_ARGS = KDB_ENABLE_REG_READ
+				      << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_REG_WRITE_NO_ARGS = KDB_ENABLE_REG_WRITE
+				       << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_INSPECT_NO_ARGS = KDB_ENABLE_INSPECT
+				     << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_FLOW_CTRL_NO_ARGS = KDB_ENABLE_FLOW_CTRL
+				       << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_SIGNAL_NO_ARGS = KDB_ENABLE_SIGNAL
+				    << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_REBOOT_NO_ARGS = KDB_ENABLE_REBOOT
+				    << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_ALWAYS_SAFE_NO_ARGS = KDB_ENABLE_ALWAYS_SAFE
+					 << KDB_ENABLE_NO_ARGS_SHIFT,
+	KDB_ENABLE_MASK_NO_ARGS = KDB_ENABLE_MASK << KDB_ENABLE_NO_ARGS_SHIFT,
+
+	KDB_REPEAT_NO_ARGS = 0x40000000, /* Repeat the command w/o arguments */
+	KDB_REPEAT_WITH_ARGS = 0x80000000, /* Repeat the command with args */
 } kdb_cmdflags_t;
 
 typedef int (*kdb_func_t)(int, const char **);

kernel/debug/kdb/kdb_bp.c

@@ -532,21 +532,28 @@ void __init kdb_initbptab(void)
 		bp->bp_free = 1;
 
 	kdb_register_flags("bp", kdb_bp, "[<vaddr>]",
-		"Set/Display breakpoints", 0, KDB_REPEAT_NO_ARGS);
+		"Set/Display breakpoints", 0,
+		KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS);
 	kdb_register_flags("bl", kdb_bp, "[<vaddr>]",
-		"Display breakpoints", 0, KDB_REPEAT_NO_ARGS);
+		"Display breakpoints", 0,
+		KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS);
 	if (arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT)
 		kdb_register_flags("bph", kdb_bp, "[<vaddr>]",
-		"[datar [length]|dataw [length]]   Set hw brk", 0, KDB_REPEAT_NO_ARGS);
+		"[datar [length]|dataw [length]]   Set hw brk", 0,
+		KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS);
 	kdb_register_flags("bc", kdb_bc, "<bpnum>",
-		"Clear Breakpoint", 0, 0);
+		"Clear Breakpoint", 0,
+		KDB_ENABLE_FLOW_CTRL);
 	kdb_register_flags("be", kdb_bc, "<bpnum>",
-		"Enable Breakpoint", 0, 0);
+		"Enable Breakpoint", 0,
+		KDB_ENABLE_FLOW_CTRL);
 	kdb_register_flags("bd", kdb_bc, "<bpnum>",
-		"Disable Breakpoint", 0, 0);
+		"Disable Breakpoint", 0,
+		KDB_ENABLE_FLOW_CTRL);
 
 	kdb_register_flags("ss", kdb_ss, "",
-		"Single Step", 1, KDB_REPEAT_NO_ARGS);
+		"Single Step", 1,
+		KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS);
 	/*
 	 * Architecture dependent initialization.
 	 */

kernel/debug/kdb/kdb_main.c

@@ -187,6 +187,26 @@ struct task_struct *kdb_curr_task(int cpu)
 	return p;
 }
 
+/*
+ * Check whether the flags of the current command and the permissions
+ * of the kdb console has allow a command to be run.
+ */
+static inline bool kdb_check_flags(kdb_cmdflags_t flags, int permissions,
+				   bool no_args)
+{
+	/* permissions comes from userspace so needs massaging slightly */
+	permissions &= KDB_ENABLE_MASK;
+	permissions |= KDB_ENABLE_ALWAYS_SAFE;
+
+	/* some commands change group when launched with no arguments */
+	if (no_args)
+		permissions |= permissions << KDB_ENABLE_NO_ARGS_SHIFT;
+
+	flags |= KDB_ENABLE_ALL;
+
+	return permissions & flags;
+}
+
 /*
  * kdbgetenv - This function will return the character string value of
  *	an environment variable.
@@ -641,8 +661,13 @@ static int kdb_defcmd2(const char *cmdstr, const char *argv0)
 		if (!s->count)
 			s->usable = 0;
 		if (s->usable)
-			kdb_register(s->name, kdb_exec_defcmd,
-				     s->usage, s->help, 0);
+			/* macros are always safe because when executed each
+			 * internal command re-enters kdb_parse() and is
+			 * safety checked individually.
+			 */
+			kdb_register_flags(s->name, kdb_exec_defcmd, s->usage,
+					   s->help, 0,
+					   KDB_ENABLE_ALWAYS_SAFE);
 		return 0;
 	}
 	if (!s->usable)
@@ -2757,78 +2782,107 @@ static void __init kdb_inittab(void)
 
 	kdb_register_flags("md", kdb_md, "<vaddr>",
 	  "Display Memory Contents, also mdWcN, e.g. md8c1", 1,
-			    KDB_REPEAT_NO_ARGS);
+	  KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS);
 	kdb_register_flags("mdr", kdb_md, "<vaddr> <bytes>",
-	  "Display Raw Memory", 0, KDB_REPEAT_NO_ARGS);
+	  "Display Raw Memory", 0,
+	  KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS);
 	kdb_register_flags("mdp", kdb_md, "<paddr> <bytes>",
-	  "Display Physical Memory", 0, KDB_REPEAT_NO_ARGS);
+	  "Display Physical Memory", 0,
+	  KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS);
 	kdb_register_flags("mds", kdb_md, "<vaddr>",
-	  "Display Memory Symbolically", 0, KDB_REPEAT_NO_ARGS);
+	  "Display Memory Symbolically", 0,
+	  KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS);
 	kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>",
-	  "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS);
+	  "Modify Memory Contents", 0,
+	  KDB_ENABLE_MEM_WRITE | KDB_REPEAT_NO_ARGS);
 	kdb_register_flags("go", kdb_go, "[<vaddr>]",
-	  "Continue Execution", 1, 0);
+	  "Continue Execution", 1,
+	  KDB_ENABLE_REG_WRITE | KDB_ENABLE_ALWAYS_SAFE_NO_ARGS);
 	kdb_register_flags("rd", kdb_rd, "",
-	  "Display Registers", 0, 0);
+	  "Display Registers", 0,
+	  KDB_ENABLE_REG_READ);
 	kdb_register_flags("rm", kdb_rm, "<reg> <contents>",
-	  "Modify Registers", 0, 0);
+	  "Modify Registers", 0,
+	  KDB_ENABLE_REG_WRITE);
 	kdb_register_flags("ef", kdb_ef, "<vaddr>",
-	  "Display exception frame", 0, 0);
+	  "Display exception frame", 0,
+	  KDB_ENABLE_MEM_READ);
 	kdb_register_flags("bt", kdb_bt, "[<vaddr>]",
-	  "Stack traceback", 1, 0);
+	  "Stack traceback", 1,
+	  KDB_ENABLE_MEM_READ | KDB_ENABLE_INSPECT_NO_ARGS);
 	kdb_register_flags("btp", kdb_bt, "<pid>",
-	  "Display stack for process <pid>", 0, 0);
+	  "Display stack for process <pid>", 0,
+	  KDB_ENABLE_INSPECT);
 	kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]",
-	  "Backtrace all processes matching state flag", 0, 0);
+	  "Backtrace all processes matching state flag", 0,
+	  KDB_ENABLE_INSPECT);
 	kdb_register_flags("btc", kdb_bt, "",
-	  "Backtrace current process on each cpu", 0, 0);
+	  "Backtrace current process on each cpu", 0,
+	  KDB_ENABLE_INSPECT);
 	kdb_register_flags("btt", kdb_bt, "<vaddr>",
 	  "Backtrace process given its struct task address", 0,
-			    0);
+	  KDB_ENABLE_MEM_READ | KDB_ENABLE_INSPECT_NO_ARGS);
 	kdb_register_flags("env", kdb_env, "",
-	  "Show environment variables", 0, 0);
+	  "Show environment variables", 0,
+	  KDB_ENABLE_ALWAYS_SAFE);
 	kdb_register_flags("set", kdb_set, "",
-	  "Set environment variables", 0, 0);
+	  "Set environment variables", 0,
+	  KDB_ENABLE_ALWAYS_SAFE);
 	kdb_register_flags("help", kdb_help, "",
-	  "Display Help Message", 1, 0);
+	  "Display Help Message", 1,
+	  KDB_ENABLE_ALWAYS_SAFE);
 	kdb_register_flags("?", kdb_help, "",
-	  "Display Help Message", 0, 0);
+	  "Display Help Message", 0,
+	  KDB_ENABLE_ALWAYS_SAFE);
 	kdb_register_flags("cpu", kdb_cpu, "<cpunum>",
-	  "Switch to new cpu", 0, 0);
+	  "Switch to new cpu", 0,
+	  KDB_ENABLE_ALWAYS_SAFE_NO_ARGS);
 	kdb_register_flags("kgdb", kdb_kgdb, "",
 	  "Enter kgdb mode", 0, 0);
 	kdb_register_flags("ps", kdb_ps, "[<flags>|A]",
-	  "Display active task list", 0, 0);
+	  "Display active task list", 0,
+	  KDB_ENABLE_INSPECT);
 	kdb_register_flags("pid", kdb_pid, "<pidnum>",
-	  "Switch to another task", 0, 0);
+	  "Switch to another task", 0,
+	  KDB_ENABLE_INSPECT);
 	kdb_register_flags("reboot", kdb_reboot, "",
-	  "Reboot the machine immediately", 0, 0);
+	  "Reboot the machine immediately", 0,
+	  KDB_ENABLE_REBOOT);
 #if defined(CONFIG_MODULES)
 	kdb_register_flags("lsmod", kdb_lsmod, "",
-	  "List loaded kernel modules", 0, 0);
+	  "List loaded kernel modules", 0,
+	  KDB_ENABLE_INSPECT);
 #endif
 #if defined(CONFIG_MAGIC_SYSRQ)
 	kdb_register_flags("sr", kdb_sr, "<key>",
-	  "Magic SysRq key", 0, 0);
+	  "Magic SysRq key", 0,
+	  KDB_ENABLE_ALWAYS_SAFE);
 #endif
 #if defined(CONFIG_PRINTK)
 	kdb_register_flags("dmesg", kdb_dmesg, "[lines]",
-	  "Display syslog buffer", 0, 0);
+	  "Display syslog buffer", 0,
+	  KDB_ENABLE_ALWAYS_SAFE);
 #endif
 	if (arch_kgdb_ops.enable_nmi) {
 		kdb_register_flags("disable_nmi", kdb_disable_nmi, "",
-		  "Disable NMI entry to KDB", 0, 0);
+		  "Disable NMI entry to KDB", 0,
+		  KDB_ENABLE_ALWAYS_SAFE);
 	}
 	kdb_register_flags("defcmd", kdb_defcmd, "name \"usage\" \"help\"",
-	  "Define a set of commands, down to endefcmd", 0, 0);
+	  "Define a set of commands, down to endefcmd", 0,
+	  KDB_ENABLE_ALWAYS_SAFE);
 	kdb_register_flags("kill", kdb_kill, "<-signal> <pid>",
-	  "Send a signal to a process", 0, 0);
+	  "Send a signal to a process", 0,
+	  KDB_ENABLE_SIGNAL);
 	kdb_register_flags("summary", kdb_summary, "",
-	  "Summarize the system", 4, 0);
+	  "Summarize the system", 4,
+	  KDB_ENABLE_ALWAYS_SAFE);
 	kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]",
-	  "Display per_cpu variables", 3, 0);
+	  "Display per_cpu variables", 3,
+	  KDB_ENABLE_MEM_READ);
 	kdb_register_flags("grephelp", kdb_grep_help, "",
-	  "Display help on | grep", 0, 0);
+	  "Display help on | grep", 0,
+	  KDB_ENABLE_ALWAYS_SAFE);
 }
 
 /* Execute any commands defined in kdb_cmds.  */

kernel/trace/trace_kdb.c

@@ -128,7 +128,7 @@ static int kdb_ftdump(int argc, const char **argv)
 static __init int kdb_ftrace_register(void)
 {
 	kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]",
-			    "Dump ftrace log", 0, 0);
+			    "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE);
 	return 0;
 }