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Subject[PATCH 25/40] printk,kdb: capture printk() when in kdb shell
Date
Certain calls from the kdb shell will call out to printk(), and any of
these calls should get vectored back to the kdb_printf() so that the
kdb pager and processing can be used, as well as to properly channel
I/O to the polled I/O devices.

CC: Randy Dunlap <randy.dunlap@oracle.com>
CC: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
---
include/linux/kdb.h | 3 +++
kernel/debug/kdb/kdb_bt.c | 2 ++
kernel/debug/kdb/kdb_io.c | 24 ++++++++++++++++++++----
kernel/debug/kdb/kdb_main.c | 4 ++++
kernel/printk.c | 9 +++++++++
5 files changed, 38 insertions(+), 4 deletions(-)
diff --git a/include/linux/kdb.h b/include/linux/kdb.h
index bff071e..118fd49 100644
--- a/include/linux/kdb.h
+++ b/include/linux/kdb.h
@@ -80,6 +80,9 @@ typedef enum {
KDB_REASON_SSTEP, /* Single Step trap. - regs valid */
} kdb_reason_t;

+extern int kdb_trap_printk;
+extern int vkdb_printf(const char *fmt, va_list args)
+ __attribute__ ((format (printf, 1, 0)));
extern int kdb_printf(const char *, ...)
__attribute__ ((format (printf, 1, 2)));
typedef int (*kdb_printf_t)(const char *, ...)
diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
index c73402c..176da1a 100644
--- a/kernel/debug/kdb/kdb_bt.c
+++ b/kernel/debug/kdb/kdb_bt.c
@@ -23,6 +23,7 @@ static void kdb_show_stack(struct task_struct *p, void *addr)
{
int old_lvl = console_loglevel;
console_loglevel = 15;
+ kdb_trap_printk++;
kdb_set_current_task(p);
if (addr) {
show_stack((struct task_struct *)p, addr);
@@ -36,6 +37,7 @@ static void kdb_show_stack(struct task_struct *p, void *addr)
show_stack(p, NULL);
}
console_loglevel = old_lvl;
+ kdb_trap_printk--;
}

/*
diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index 32d5521..dd75c20 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -29,6 +29,7 @@
#define CMD_BUFLEN 256
char kdb_prompt_str[CMD_BUFLEN];

+int kdb_trap_printk;

static void kgdb_transition_check(char *buffer)
{
@@ -532,12 +533,12 @@ static int kdb_search_string(char *searched, char *searchfor)
return 0;
}

-int kdb_printf(const char *fmt, ...)
+int vkdb_printf(const char *fmt, va_list ap)
{
- va_list ap;
int diag;
int linecount;
int logging, saved_loglevel = 0;
+ int saved_trap_printk;
int got_printf_lock = 0;
int retlen = 0;
int fnd, len;
@@ -548,6 +549,9 @@ int kdb_printf(const char *fmt, ...)
unsigned long uninitialized_var(flags);

preempt_disable();
+ saved_trap_printk = kdb_trap_printk;
+ kdb_trap_printk = 0;
+
/* Serialize kdb_printf if multiple cpus try to write at once.
* But if any cpu goes recursive in kdb, just print the output,
* even if it is interleaved with any other text.
@@ -574,9 +578,7 @@ int kdb_printf(const char *fmt, ...)
next_avail = kdb_buffer;
size_avail = sizeof(kdb_buffer);
}
- va_start(ap, fmt);
vsnprintf(next_avail, size_avail, fmt, ap);
- va_end(ap);

/*
* If kdb_parse() found that the command was cmd xxx | grep yyy
@@ -804,6 +806,20 @@ kdb_print_out:
} else {
__release(kdb_printf_lock);
}
+ kdb_trap_printk = saved_trap_printk;
preempt_enable();
return retlen;
}
+
+int kdb_printf(const char *fmt, ...)
+{
+ va_list ap;
+ int r;
+
+ va_start(ap, fmt);
+ r = vkdb_printf(fmt, ap);
+ va_end(ap);
+
+ return r;
+}
+
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 59bb68d..852e003 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -1056,7 +1056,9 @@ static void kdb_dumpregs(struct pt_regs *regs)
{
int old_lvl = console_loglevel;
console_loglevel = 15;
+ kdb_trap_printk++;
show_regs(regs);
+ kdb_trap_printk--;
kdb_printf("\n");
console_loglevel = old_lvl;
}
@@ -1837,7 +1839,9 @@ static int kdb_sr(int argc, const char **argv)
__sysrq_enabled = 1;
}

+ kdb_trap_printk++;
handle_sysrq(*argv[1], NULL);
+ kdb_trap_printk--;

return 0;
}
diff --git a/kernel/printk.c b/kernel/printk.c
index 9bee02e..cd17a79 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -33,6 +33,7 @@
#include <linux/bootmem.h>
#include <linux/syscalls.h>
#include <linux/kexec.h>
+#include <linux/kdb.h>
#include <linux/ratelimit.h>
#include <linux/kmsg_dump.h>

@@ -609,6 +610,14 @@ asmlinkage int printk(const char *fmt, ...)
va_list args;
int r;

+#ifdef CONFIG_KGDB_KDB
+ if (unlikely(kdb_trap_printk)) {
+ va_start(args, fmt);
+ r = vkdb_printf(fmt, args);
+ va_end(args);
+ return r;
+ }
+#endif
va_start(args, fmt);
r = vprintk(fmt, args);
va_end(args);
--
1.6.3.1.9.g95405b


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