Messages in this thread | | | From | Saravana Kannan <> | Date | Tue, 30 Aug 2022 00:20:00 -0700 | Subject | Re: [PATCH v2] ARM: Add sanity check for dev->periphid in amba_probe() |
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On Mon, Aug 29, 2022 at 11:59 PM Zhen Lei <thunder.leizhen@huawei.com> wrote: > > Commit f2d3b9a46e0e ("ARM: 9220/1: amba: Remove deferred device addition") > forcibly invokes device_add() even if dev->periphid is not ready. Although > it will be remedied in amba_match(): dev->periphid will be initialized > if everything is in place; Otherwise, return -EPROBE_DEFER to block > __driver_attach() from further execution. But not all drivers have .match > hook, such as pl031, the dev->bus->probe will be called directly in > __driver_attach(). Unfortunately, if dev->periphid is still not > initialized, the following exception will be triggered. > > 8<--- cut here --- > Unable to handle kernel NULL pointer dereference at virtual address 00000008 > [00000008] *pgd=00000000 > Internal error: Oops: 5 [#1] SMP ARM > Modules linked in: > CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.0.0-rc2+ #7 > Hardware name: ARM-Versatile Express > PC is at pl031_probe+0x8/0x208 > LR is at amba_probe+0xf0/0x160 > pc : 80698df8 lr : 8050eb54 psr: 80000013 > sp : c0825df8 ip : 00000000 fp : 811fda38 > r10: 00000000 r9 : 80d72470 r8 : fffffdfb > r7 : 811fd800 r6 : be7eb330 r5 : 00000000 r4 : 811fd900 > r3 : 80698df0 r2 : 37000000 r1 : 00000000 r0 : 811fd800 > Flags: Nzcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none > Control: 10c5387d Table: 6000406a DAC: 00000051 > ... ... > pl031_probe from amba_probe+0xf0/0x160 > amba_probe from really_probe+0x118/0x290 > really_probe from __driver_probe_device+0x84/0xe4 > __driver_probe_device from driver_probe_device+0x30/0xd0 > driver_probe_device from __driver_attach+0x8c/0xfc > __driver_attach from bus_for_each_dev+0x70/0xb0 > bus_for_each_dev from bus_add_driver+0x168/0x1f4 > bus_add_driver from driver_register+0x7c/0x118 > driver_register from do_one_initcall+0x44/0x1ec > do_one_initcall from kernel_init_freeable+0x238/0x288 > kernel_init_freeable from kernel_init+0x18/0x12c > kernel_init from ret_from_fork+0x14/0x2c > ... ... > ---[ end trace 0000000000000000 ]--- > > Therefore, take the same action as in amba_match(): return -EPROBE_DEFER > if dev->periphid is not ready in amba_probe(). > > Fixes: f2d3b9a46e0e ("ARM: 9220/1: amba: Remove deferred device addition") > Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> > --- > KernelVersion: v6.0-rc3 > drivers/amba/bus.c | 24 +++++++++++++++++++++--- > 1 file changed, 21 insertions(+), 3 deletions(-) > > v1 --> v2: > 1. Update this patch based on: > https://lore.kernel.org/lkml/20220818172852.3548-1-isaacmanjarres@google.com/ > 2. Move the operations of sanity checking and reading dev->periphid, > updating uevent into new function amba_prepare_periphid(). > > diff --git a/drivers/amba/bus.c b/drivers/amba/bus.c > index 110a535648d2e1f..8e4c7e190880206 100644 > --- a/drivers/amba/bus.c > +++ b/drivers/amba/bus.c > @@ -204,10 +204,9 @@ static int amba_read_periphid(struct amba_device *dev) > return ret; > } > > -static int amba_match(struct device *dev, struct device_driver *drv) > +static int amba_prepare_periphid(struct device *dev) > { > struct amba_device *pcdev = to_amba_device(dev); > - struct amba_driver *pcdrv = to_amba_driver(drv); > > mutex_lock(&pcdev->periphid_lock); > if (!pcdev->periphid) { > @@ -228,6 +227,19 @@ static int amba_match(struct device *dev, struct device_driver *drv) > } > mutex_unlock(&pcdev->periphid_lock); > > + return 0; > +} > + > +static int amba_match(struct device *dev, struct device_driver *drv) > +{ > + struct amba_device *pcdev = to_amba_device(dev); > + struct amba_driver *pcdrv = to_amba_driver(drv); > + int ret; > + > + ret = amba_prepare_periphid(dev); > + if (ret) > + return ret; > + > /* When driver_override is set, only bind to the matching driver */ > if (pcdev->driver_override) > return !strcmp(pcdev->driver_override, drv->name); > @@ -278,9 +290,15 @@ static int amba_probe(struct device *dev) > { > struct amba_device *pcdev = to_amba_device(dev); > struct amba_driver *pcdrv = to_amba_driver(dev->driver); > - const struct amba_id *id = amba_lookup(pcdrv->id_table, pcdev); > + const struct amba_id *id; > int ret; > > + ret = amba_prepare_periphid(dev); > + if (ret) > + return ret; > + > + id = amba_lookup(pcdrv->id_table, pcdev); > + > do { > ret = of_amba_device_decode_irq(pcdev); > if (ret)
Let's wait for Isaac to review this. He has been looking at the locking issue for a bit and there were some tricky cases.
-Saravana
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