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Commit 04a41849 authored by Thomas Meyer's avatar Thomas Meyer Committed by Richard Weinberger
Browse files

um: add a kmsg_dumper 



Add a kmsg_dumper, that dumps the kmsg buffer to stdout, when no console
is available. This an enables the printing of early panic() calls
triggered in uml_postsetup().
When a panic() call happens so early in the UML kernel no
earlyprintk/console is available yet, but with a kmsg_dumper in place
the kernel message buffer will be outputted to the user, to give a
better hint, of what the failure was.

Signed-off-by: default avatarThomas Meyer <thomas@m3y3r.de>
Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
parent fc9bea0e

arch/um/kernel/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -13,7 +13,7 @@ clean-files := 
obj-y = config.o exec.o exitcode.o irq.o ksyms.o mem.o \

	physmem.o process.o ptrace.o reboot.o sigio.o \

	signal.o syscall.o sysrq.o time.o tlb.o trap.o \

	um_arch.o umid.o maccess.o skas/

	um_arch.o umid.o maccess.o kmsg_dump.o skas/



obj-$(CONFIG_BLK_DEV_INITRD) += initrd.o

obj-$(CONFIG_GPROF)	+= gprof_syms.o

arch/um/kernel/kmsg_dump.c

0 → 100644
+43 −0
Original line number Diff line number Diff line 
#include <linux/kmsg_dump.h>

#include <linux/console.h>

#include <shared/init.h>

#include <shared/kern.h>

#include <os.h>



static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,

				enum kmsg_dump_reason reason)

{

	static char line[1024];



	size_t len = 0;

	bool con_available = false;



	/* only dump kmsg when no console is available */

	if (!console_trylock())

		return;



	if (console_drivers != NULL)

		con_available = true;



	console_unlock();



	if (con_available == true)

		return;



	printf("kmsg_dump:\n");

	while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len)) {

		line[len] = '\0';

		printf("%s", line);

	}

}



static struct kmsg_dumper kmsg_dumper = {

	.dump = kmsg_dumper_stdout

};



int __init kmsg_dumper_stdout_init(void)

{

	return kmsg_dump_register(&kmsg_dumper);

}



__uml_postsetup(kmsg_dumper_stdout_init);

arch/um/kernel/um_arch.c

+2 −0
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ 
#include <linux/string.h>

#include <linux/utsname.h>

#include <linux/sched.h>

#include <linux/kmsg_dump.h>

#include <asm/pgtable.h>

#include <asm/processor.h>

#include <asm/sections.h>
@@ -211,6 +212,7 @@ static void __init uml_postsetup(void) 
static int panic_exit(struct notifier_block *self, unsigned long unused1,

		      void *unused2)

{

	kmsg_dump(KMSG_DUMP_PANIC);

	bust_spinlocks(1);

	bust_spinlocks(0);

	uml_exitcode = 1;