----- Original Message -----
> From: "Thomas Meyer" <tho...@m3y3r.de>
> To: "user-mode-linux-devel" <user-mode-linux-devel@lists.sourceforge.net>
> Cc: "Richard Weinberger" <rich...@nod.at>, "Daniel Walter" <d.wal...@0x90.at>
> Sent: Thursday, October 9, 2014 6:55:34 PM
> Subject: [PATCH 2/2] um: add a kmsg_dumper
>
>
> Add a kmsg_dumper, that dumps the kmsg buffer to stderr, when no
> console is available.
> This an enables the printing of early panic() calls triggered in
> uml_postsetup().
>
> Signed-off-by: Thomas Meyer <tho...@m3y3r.de>
> ---
> arch/um/drivers/ubd_kern.c | 5 +++--
> arch/um/include/shared/os.h | 1 +
> arch/um/kernel/Makefile | 2 +-
> arch/um/kernel/kmsg_dump.c | 44
> ++++++++++++++++++++++++++++++++++++++++++++
> arch/um/kernel/um_arch.c | 2 ++
> arch/um/os-Linux/util.c | 12 ++++++++++++
> 6 files changed, 63 insertions(+), 3 deletions(-)
> create mode 100644 arch/um/kernel/kmsg_dump.c
>
> diff --git a/arch/um/include/shared/os.h
> b/arch/um/include/shared/os.h
> index 08eec0b..36741f4 100644
> --- a/arch/um/include/shared/os.h
> +++ b/arch/um/include/shared/os.h
> @@ -238,6 +238,7 @@ extern void setup_hostinfo(char *buf, int len);
> extern void os_dump_core(void) __attribute__ ((noreturn));
> extern void um_early_printk(const char *s, unsigned int n);
> extern void os_fix_helper_signals(void);
> +extern int os_printf_stderr(const char *fmt, ...);
>
> /* time.c */
> extern void idle_sleep(unsigned long long nsecs);
> diff --git a/arch/um/kernel/Makefile b/arch/um/kernel/Makefile
> index d8b78a0..572e781 100644
> --- a/arch/um/kernel/Makefile
> +++ b/arch/um/kernel/Makefile
> @@ -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 smp.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
> diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
> new file mode 100644
> index 0000000..8047ca5a3
> --- /dev/null
> +++ b/arch/um/kernel/kmsg_dump.c
> @@ -0,0 +1,44 @@
> +#include <linux/kmsg_dump.h>
> +#include <linux/console.h>
> +#include <shared/init.h>
> +#include <shared/kern.h>
> +#include <os.h>
> +
> +static struct kmsg_dumper kmsg_dumper;
can you make this const ?
> +
> +static void kmsg_dumper_stderr(struct kmsg_dumper *dumper,
> + enum kmsg_dump_reason reason)
> +{
> + static char line[1024];
> +
> + size_t len = 0;
> + int con_count = 0;
> + struct console *con = NULL;
> +
> + /* only dump kmsg when no console is available */
> + if (!console_trylock()) {
> + return;
> + }
> + for_each_console(con) {
> + con_count++;
> + }
> + console_unlock();
> +
> + if (con_count > 0) {
> + return;
> + }
> +
Would it be sufficient to check if a console exists, instead of iterating
through all of
them and decide to return anyway as soon as one exists ? (I believe a check for
console_drivers != NULL should be sufficient)
> + os_printf_stderr("kmsg_dump:\n");
> + while (kmsg_dump_get_line(dumper, true, line, sizeof(line), &len))
> {
> + line[len] = '\0';
> + os_printf_stderr("%s", line);
> + }
> +}
> +
> +int __init kmsg_dumper_stderr_init(void)
> +{
> + kmsg_dumper.dump = kmsg_dumper_stderr;
> + return kmsg_dump_register(&kmsg_dumper);
> +}
> +
> +__uml_initcall(kmsg_dumper_stderr_init);
> diff --git a/arch/um/kernel/um_arch.c b/arch/um/kernel/um_arch.c
> index ab72560..4f6fc24 100644
> --- a/arch/um/kernel/um_arch.c
> +++ b/arch/um/kernel/um_arch.c
> @@ -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>
> @@ -234,6 +235,7 @@ 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;
> diff --git a/arch/um/os-Linux/util.c b/arch/um/os-Linux/util.c
> index faee55e..a4cc3a0 100644
> --- a/arch/um/os-Linux/util.c
> +++ b/arch/um/os-Linux/util.c
> @@ -152,3 +152,15 @@ void um_early_printk(const char *s, unsigned int
> n)
> {
> printf("%.*s", n, s);
> }
> +
> +int os_printf_stderr(const char *fmt, ...)
> +{
> + va_list list;
> + int rc;
> +
> + va_start(list, fmt);
> + rc = vfprintf(stderr, fmt, list);
> + va_end(list);
> +
> + return rc;
> +}
Is there a reason why you want the dump to be on stderr ? It seems
the rest of uml just prints to stdout ?
> --
> 1.9.3
>
>
>
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