kmalloc before kmem_cache_init

Hi Sukanto,

On Sat, Jan 28, 2012 at 11:25 PM, Sukanto Ghosh
[off-list ref] wrote:

Hi Dave,

If you look into start_kernel() the call to parse_early_param()
precedes mm_init().
parse_early_param() eventually calls do_early_param().
do_early_param() parses for "earlycon" in kernel commandline and then calls the
setup_function associated with earlycon.

I have in my commandline: earlycon=uart8250,mmio32,0x10000000,9600

Call flow starting from drivers/tty/serial/8250_early.c will lead to kmalloc

early_param("early_con", setup_early_serial8250_console)
? setup_early_serial8250_console()
? ? ? early_serial8250_setup()
? ? ? ? ? parse_options()
? ? ? ? ? ? ? ioremap_nocache()
? ? ? ? ? ? ? ? ?... arch-specific-ioremap
? ? ? ? ? ? ? ? ? ? ? ?-- some form of arch specific __ioremap_caller
? ? ? ? ? ? ? ? ? ? ? ? ? ?--- get_vm_area_caller()
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?__get_vm_area_node
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? kzalloc_node
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? kmalloc_node
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?kmalloc

It looks like CONFIG_FIX_EARLYCON_MEM defaults to y (on x86 anyways),
so this would cause the path that doesn't call ioremam_nocache to be
taken.

I'm guessing that if you specify earycon, then you also need to ensure
that CONFIG_FIX_EARLYCON is set.

You didn't mention which architecture you were using. ARM has an
early_printk which is sort of like an early console.

-- 
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com