summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2020-06-27 08:53:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-27 08:53:49 -0700
commit6116dea80dfd5b8d3825bf7f2e44a8bc2730f3d0 (patch)
tree729a8797b2a27ab9a1b6d38cb4a67b789e2238fa
parent21d2f6850c09fdec730c11d35406da1dc541432d (diff)
parent440ab9e10e2e6e5fd677473ee6f9e3af0f6904d6 (diff)
Merge tag 'kgdb-5.8-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux
Pull kgdb fixes from Daniel Thompson: "The main change here is a fix for a number of unsafe interactions between kdb and the console system. The fixes are specific to kdb (pure kgdb debugging does not use the console system at all). On systems with an NMI then kdb, if it is enabled, must get messages to the user despite potentially running from some "difficult" calling contexts. These fixes avoid using the console system where we have been provided an alternative (safer) way to interact with the user and, if using the console system in unavoidable, use oops_in_progress for deadlock avoidance. These fixes also ensure kdb honours the console enable flag. Also included is a fix that wraps kgdb trap handling in an RCU read lock to avoids triggering diagnostic warnings. This is a wide lock scope but this is OK because kgdb is a stop-the-world debugger. When we stop the world we put all the CPUs into holding pens and this inhibits RCU update anyway" * tag 'kgdb-5.8-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/danielt/linux: kgdb: Avoid suspicious RCU usage warning kdb: Switch to use safer dbg_io_ops over console APIs kdb: Make kdb_printf() console handling more robust kdb: Check status of console prior to invoking handlers kdb: Re-factor kdb_printf() message write code
-rw-r--r--drivers/tty/serial/kgdb_nmi.c2
-rw-r--r--drivers/tty/serial/kgdboc.c32
-rw-r--r--drivers/usb/early/ehci-dbgp.c3
-rw-r--r--include/linux/kgdb.h5
-rw-r--r--kernel/debug/debug_core.c4
-rw-r--r--kernel/debug/kdb/kdb_io.c72
6 files changed, 68 insertions, 50 deletions
diff --git a/drivers/tty/serial/kgdb_nmi.c b/drivers/tty/serial/kgdb_nmi.c
index 5022447afa23..6004c0c1d173 100644
--- a/drivers/tty/serial/kgdb_nmi.c
+++ b/drivers/tty/serial/kgdb_nmi.c
@@ -50,7 +50,7 @@ static int kgdb_nmi_console_setup(struct console *co, char *options)
* I/O utilities that messages sent to the console will automatically
* be displayed on the dbg_io.
*/
- dbg_io_ops->is_console = true;
+ dbg_io_ops->cons = co;
return 0;
}
diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index 41396982e9e0..84ffede27f23 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -45,7 +45,6 @@ static struct platform_device *kgdboc_pdev;
#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static struct kgdb_io kgdboc_earlycon_io_ops;
-static struct console *earlycon;
static int (*earlycon_orig_exit)(struct console *con);
#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
@@ -145,7 +144,7 @@ static void kgdboc_unregister_kbd(void)
#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
static void cleanup_earlycon(void)
{
- if (earlycon)
+ if (kgdboc_earlycon_io_ops.cons)
kgdb_unregister_io_module(&kgdboc_earlycon_io_ops);
}
#else /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
@@ -178,7 +177,7 @@ static int configure_kgdboc(void)
goto noconfig;
}
- kgdboc_io_ops.is_console = 0;
+ kgdboc_io_ops.cons = NULL;
kgdb_tty_driver = NULL;
kgdboc_use_kms = 0;
@@ -198,7 +197,7 @@ static int configure_kgdboc(void)
int idx;
if (cons->device && cons->device(cons, &idx) == p &&
idx == tty_line) {
- kgdboc_io_ops.is_console = 1;
+ kgdboc_io_ops.cons = cons;
break;
}
}
@@ -433,7 +432,8 @@ static int kgdboc_earlycon_get_char(void)
{
char c;
- if (!earlycon->read(earlycon, &c, 1))
+ if (!kgdboc_earlycon_io_ops.cons->read(kgdboc_earlycon_io_ops.cons,
+ &c, 1))
return NO_POLL_CHAR;
return c;
@@ -441,7 +441,8 @@ static int kgdboc_earlycon_get_char(void)
static void kgdboc_earlycon_put_char(u8 chr)
{
- earlycon->write(earlycon, &chr, 1);
+ kgdboc_earlycon_io_ops.cons->write(kgdboc_earlycon_io_ops.cons, &chr,
+ 1);
}
static void kgdboc_earlycon_pre_exp_handler(void)
@@ -461,7 +462,7 @@ static void kgdboc_earlycon_pre_exp_handler(void)
* boot if we detect this case.
*/
for_each_console(con)
- if (con == earlycon)
+ if (con == kgdboc_earlycon_io_ops.cons)
return;
already_warned = true;
@@ -484,25 +485,25 @@ static int kgdboc_earlycon_deferred_exit(struct console *con)
static void kgdboc_earlycon_deinit(void)
{
- if (!earlycon)
+ if (!kgdboc_earlycon_io_ops.cons)
return;
- if (earlycon->exit == kgdboc_earlycon_deferred_exit)
+ if (kgdboc_earlycon_io_ops.cons->exit == kgdboc_earlycon_deferred_exit)
/*
* kgdboc_earlycon is exiting but original boot console exit
* was never called (AKA kgdboc_earlycon_deferred_exit()
* didn't ever run). Undo our trap.
*/
- earlycon->exit = earlycon_orig_exit;
- else if (earlycon->exit)
+ kgdboc_earlycon_io_ops.cons->exit = earlycon_orig_exit;
+ else if (kgdboc_earlycon_io_ops.cons->exit)
/*
* We skipped calling the exit() routine so we could try to
* keep using the boot console even after it went away. We're
* finally done so call the function now.
*/
- earlycon->exit(earlycon);
+ kgdboc_earlycon_io_ops.cons->exit(kgdboc_earlycon_io_ops.cons);
- earlycon = NULL;
+ kgdboc_earlycon_io_ops.cons = NULL;
}
static struct kgdb_io kgdboc_earlycon_io_ops = {
@@ -511,7 +512,6 @@ static struct kgdb_io kgdboc_earlycon_io_ops = {
.write_char = kgdboc_earlycon_put_char,
.pre_exception = kgdboc_earlycon_pre_exp_handler,
.deinit = kgdboc_earlycon_deinit,
- .is_console = true,
};
#define MAX_CONSOLE_NAME_LEN (sizeof((struct console *) 0)->name)
@@ -557,10 +557,10 @@ static int __init kgdboc_earlycon_init(char *opt)
goto unlock;
}
- earlycon = con;
+ kgdboc_earlycon_io_ops.cons = con;
pr_info("Going to register kgdb with earlycon '%s'\n", con->name);
if (kgdb_register_io_module(&kgdboc_earlycon_io_ops) != 0) {
- earlycon = NULL;
+ kgdboc_earlycon_io_ops.cons = NULL;
pr_info("Failed to register kgdb with earlycon\n");
} else {
/* Trap exit so we can keep earlycon longer if needed. */
diff --git a/drivers/usb/early/ehci-dbgp.c b/drivers/usb/early/ehci-dbgp.c
index ea0d531c63e2..775cf70cfb3e 100644
--- a/drivers/usb/early/ehci-dbgp.c
+++ b/drivers/usb/early/ehci-dbgp.c
@@ -1058,7 +1058,8 @@ static int __init kgdbdbgp_parse_config(char *str)
kgdbdbgp_wait_time = simple_strtoul(ptr, &ptr, 10);
}
kgdb_register_io_module(&kgdbdbgp_io_ops);
- kgdbdbgp_io_ops.is_console = early_dbgp_console.index != -1;
+ if (early_dbgp_console.index != -1)
+ kgdbdbgp_io_ops.cons = &early_dbgp_console;
return 0;
}
diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h
index c62d76478adc..529116b0cabe 100644
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -276,8 +276,7 @@ struct kgdb_arch {
* the I/O driver.
* @post_exception: Pointer to a function that will do any cleanup work
* for the I/O driver.
- * @is_console: 1 if the end device is a console 0 if the I/O device is
- * not a console
+ * @cons: valid if the I/O device is a console; else NULL.
*/
struct kgdb_io {
const char *name;
@@ -288,7 +287,7 @@ struct kgdb_io {
void (*deinit) (void);
void (*pre_exception) (void);
void (*post_exception) (void);
- int is_console;
+ struct console *cons;
};
extern const struct kgdb_arch arch_kgdb_ops;
diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
index bc8d25f2ac8a..9e5934780f41 100644
--- a/kernel/debug/debug_core.c
+++ b/kernel/debug/debug_core.c
@@ -587,6 +587,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
arch_kgdb_ops.disable_hw_break(regs);
acquirelock:
+ rcu_read_lock();
/*
* Interrupts will be restored by the 'trap return' code, except when
* single stepping.
@@ -646,6 +647,7 @@ return_normal:
atomic_dec(&slaves_in_kgdb);
dbg_touch_watchdogs();
local_irq_restore(flags);
+ rcu_read_unlock();
return 0;
}
cpu_relax();
@@ -664,6 +666,7 @@ return_normal:
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
+ rcu_read_unlock();
goto acquirelock;
}
@@ -787,6 +790,7 @@ kgdb_restore:
raw_spin_unlock(&dbg_master_lock);
dbg_touch_watchdogs();
local_irq_restore(flags);
+ rcu_read_unlock();
return kgdb_info[cpu].ret_state;
}
diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index 924bc9298a42..683a799618ad 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -542,6 +542,44 @@ static int kdb_search_string(char *searched, char *searchfor)
return 0;
}
+static void kdb_msg_write(const char *msg, int msg_len)
+{
+ struct console *c;
+
+ if (msg_len == 0)
+ return;
+
+ if (dbg_io_ops) {
+ const char *cp = msg;
+ int len = msg_len;
+
+ while (len--) {
+ dbg_io_ops->write_char(*cp);
+ cp++;
+ }
+ }
+
+ for_each_console(c) {
+ if (!(c->flags & CON_ENABLED))
+ continue;
+ if (c == dbg_io_ops->cons)
+ continue;
+ /*
+ * Set oops_in_progress to encourage the console drivers to
+ * disregard their internal spin locks: in the current calling
+ * context the risk of deadlock is a bigger problem than risks
+ * due to re-entering the console driver. We operate directly on
+ * oops_in_progress rather than using bust_spinlocks() because
+ * the calls bust_spinlocks() makes on exit are not appropriate
+ * for this calling context.
+ */
+ ++oops_in_progress;
+ c->write(c, msg, msg_len);
+ --oops_in_progress;
+ touch_nmi_watchdog();
+ }
+}
+
int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap)
{
int diag;
@@ -553,7 +591,6 @@ int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap)
int this_cpu, old_cpu;
char *cp, *cp2, *cphold = NULL, replaced_byte = ' ';
char *moreprompt = "more> ";
- struct console *c;
unsigned long uninitialized_var(flags);
/* Serialize kdb_printf if multiple cpus try to write at once.
@@ -687,22 +724,11 @@ kdb_printit:
*/
retlen = strlen(kdb_buffer);
cp = (char *) printk_skip_headers(kdb_buffer);
- if (!dbg_kdb_mode && kgdb_connected) {
+ if (!dbg_kdb_mode && kgdb_connected)
gdbstub_msg_write(cp, retlen - (cp - kdb_buffer));
- } else {
- if (dbg_io_ops && !dbg_io_ops->is_console) {
- len = retlen - (cp - kdb_buffer);
- cp2 = cp;
- while (len--) {
- dbg_io_ops->write_char(*cp2);
- cp2++;
- }
- }
- for_each_console(c) {
- c->write(c, cp, retlen - (cp - kdb_buffer));
- touch_nmi_watchdog();
- }
- }
+ else
+ kdb_msg_write(cp, retlen - (cp - kdb_buffer));
+
if (logging) {
saved_loglevel = console_loglevel;
console_loglevel = CONSOLE_LOGLEVEL_SILENT;
@@ -751,19 +777,7 @@ kdb_printit:
moreprompt = "more> ";
kdb_input_flush();
-
- if (dbg_io_ops && !dbg_io_ops->is_console) {
- len = strlen(moreprompt);
- cp = moreprompt;
- while (len--) {
- dbg_io_ops->write_char(*cp);
- cp++;
- }
- }
- for_each_console(c) {
- c->write(c, moreprompt, strlen(moreprompt));
- touch_nmi_watchdog();
- }
+ kdb_msg_write(moreprompt, strlen(moreprompt));
if (logging)
printk("%s", moreprompt);