[PATCH v11 0/5] x86/earlyprintk: setup serial earlyprintk as early as possible

Alexander Kuleshov
2015-06-09T11:11:10Z

The early_printk function is usable only after the setup_early_printk will
be executed. We pass 'earlyprintk' through the kernel command line. So, it
means that earlyprintk will be usable only after the 'parse_early_param'
will be executed or in another words earlyprintk is usable only during early
boot, kernel decompression and after call of the parse_early_param. But
there are many stuff after the kernel decompression and before the
parse_early_param will be called as memblock usage, early cpu initialization,
early ioremap initialization and etc... So earlyprintk allows us to see
what's going on there.

Patchset was tested for both x86 and x86_64 architectures with the qemu
and real hadware.

It provides call of the earlyprintk function right after the early
initialization of the serial console in the arch/x86/kernel/head{32,64.c},
so it must prints the debug string.

These patchset provides following changes:

Move handling of the builtin command line to the separate function
from the setup_arch. Now we can call it from the arch/x86/kernel/head{32,64}.c,
and find 'earlyprintk' kernel command line paramter there.

Provide setup_serial_console function to setup serial earlyprintk in the
arch/x86/kernel/head{32,64}.c

Changelog:

v11:
* setup_log_buf moved to the arch/x86/kernel/head{32,64.c} from
the arch/x86/kernel/setup.c to setup early log_buf for the earlyprintl
* Update log_buf in the early_printk function
* Added additional patch for testing earlyprintk

v10:
* Removed style issues which are not related to the patchset.

v9:
* Add call of the lockdep_init to the arch/x86/kernel/head{32,64}.c
before the serial console initialization to prevent:

[ 0.000000] WARNING: lockdep init error! lock-(console_sem).lock was acquiredbefore lockdep_init
[ 0.000000] Call stack leading to lockdep invocation was:
[ 0.000000] [] save_stack_trace+0x2f/0x50
[ 0.000000] [] __lock_acquire+0xa2c/0xf00
[ 0.000000] [] lock_acquire+0xdb/0x2b0
[ 0.000000] [] _raw_spin_lock_irqsave+0x53/0x90
[ 0.000000] [] down+0x16/0x50
[ 0.000000] [] console_lock+0x19/0x60
[ 0.000000] [] register_console+0x116/0x350
[ 0.000000] [] setup_early_printk+0x165/0x467
[ 0.000000] [] setup_early_serial_console+0x56/0x58
[ 0.000000] [] x86_64_start_kernel+0xce/0x110
[ 0.000000] [] 0xffffffffffffffff
[ 0.000000] ------------------------

during early serial console initialization.

* Add additional check to the earlyprintk initialization to protect double initialization
of the early_serial_console.
* Fixed comment.

v8:
* Fixed warning with the definition of the setup_early_serial_console in the
arch/x86/include/asm/setup.h

v7:
* Move setup_early_serial_console to the the arch/x86/include/setup.h
* Add ifdefs to prevent setup_serial_console if CONFIG_EARLY_PRINTK is not set.

v6:
* Style fixes.
* Call of the suetp_builtin_cmdline moved to the separate patch.

v5:
* Call setup_builtin_cmdline instead of setup_cmdline

v4:
* Move setup_early_serial_console from the include/linux/printk.h to the
arch/x86/include/asm/serial.h, because this function is only for x86 now.

v3:
* Call setup_cmdline before setup_early_printk;
* setup_early_printk call wrapped with the setup_early_serial_console which
checks that 'serial' given to the earlyprintk command line option. This prevents
call of the setup_early_printk with the given pciserial/dbgp/efi, because they
are using early_ioremap.

v2:
* Comment added before the setup_early_printk call;
* Added information about testing to the commit message.

Alexander Kuleshov (5):
x86/setup: introduce setup_bultin_cmdline
x86/setup: handle builtin command line as early as possible
x86/earlyprintk: Allocate log_buf as early as possible
x86/earlyprintk: setup earlyprintk as early as possible
x86/earlyprintk: Patch for testing earlyprintk

arch/x86/include/asm/setup.h | 7 +++++++
arch/x86/kernel/early_printk.c | 33 ++++++++++++++++++++++++++++++---
arch/x86/kernel/head32.c | 10 ++++++++++
arch/x86/kernel/head64.c | 11 +++++++++++
arch/x86/kernel/setup.c | 33 +++++++++++++++++----------------
init/main.c | 2 +-
kernel/printk/printk.c | 5 +++++
7 files changed, 81 insertions(+), 20 deletions(-)

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2.4.0.GIT