firmware: coreboot: Register bus in module init
The coreboot_table driver registers a coreboot bus while probing a "coreboot_table" device representing the coreboot table memory region. Probing this device (i.e., registering the bus) is a dependency for the module_init() functions of any driver for this bus (e.g., memconsole-coreboot.c / memconsole_driver_init()). With synchronous probe, this dependency works OK, as the link order in the Makefile ensures coreboot_table_driver_init() (and thus, coreboot_table_probe()) completes before a coreboot device driver tries to add itself to the bus. With asynchronous probe, however, coreboot_table_probe() may race with memconsole_driver_init(), and so we're liable to hit one of these two: 1. coreboot_driver_register() eventually hits "[...] the bus was not initialized.", and the memconsole driver fails to register; or 2. coreboot_driver_register() gets past #1, but still races with bus_register() and hits some other undefined/crashing behavior (e.g., in driver_find() [1]) We can resolve this by registering the bus in our initcall, and only deferring "device" work (scanning the coreboot memory region and creating sub-devices) to probe(). [1] Example failure, using 'driver_async_probe=*' kernel command line: [ 0.114217] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 ... [ 0.114307] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.1.0-rc1 #63 [ 0.114316] Hardware name: Google Scarlet (DT) ... [ 0.114488] Call trace: [ 0.114494] _raw_spin_lock+0x34/0x60 [ 0.114502] kset_find_obj+0x28/0x84 [ 0.114511] driver_find+0x30/0x50 [ 0.114520] driver_register+0x64/0x10c [ 0.114528] coreboot_driver_register+0x30/0x3c [ 0.114540] memconsole_driver_init+0x24/0x30 [ 0.114550] do_one_initcall+0x154/0x2e0 [ 0.114560] do_initcall_level+0x134/0x160 [ 0.114571] do_initcalls+0x60/0xa0 [ 0.114579] do_basic_setup+0x28/0x34 [ 0.114588] kernel_init_freeable+0xf8/0x150 [ 0.114596] kernel_init+0x2c/0x12c [ 0.114607] ret_from_fork+0x10/0x20 [ 0.114624] Code: 5280002b 1100054a b900092a f9800011 (885ffc01) [ 0.114631] ---[ end trace 0000000000000000 ]--- Fixes: b81e3140 ("firmware: coreboot: Make bus registration symmetric") Cc: <stable@vger.kernel.org> Signed-off-by: NBrian Norris <briannorris@chromium.org> Reviewed-by: NGuenter Roeck <linux@roeck-us.net> Reviewed-by: NStephen Boyd <swboyd@chromium.org> Link: https://lore.kernel.org/r/20221019180934.1.If29e167d8a4771b0bf4a39c89c6946ed764817b9@changeidSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
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