linux-kernel - Re: [PATCH 2/2] clk: bcm2835: Remove casting to bcm2835_clk

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Date:   Tue, 26 May 2020 16:42:09 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Michael Turquette <mturquette@...libre.com>,
        Nathan Chancellor <natechancellor@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        linux-clk@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>
Subject: Re: [PATCH 2/2] clk: bcm2835: Remove casting to bcm2835_clk_register

Quoting Nathan Chancellor (2020-05-16 01:08:07)
> There are four different callback functions that are used for the
> clk_register callback that all have different second parameter types.
> 
> bcm2835_register_pll -> struct bcm2835_pll_data
> bcm2835_register_pll_divider -> struct bcm2835_pll_divider_data
> bcm2835_register_clock -> struct bcm2835_clock_data
> bcm2835_register_date -> struct bcm2835_gate_data
> 
> These callbacks are cast to bcm2835_clk_register so that there is no
> error about incompatible pointer types. Unfortunately, this is a control
> flow integrity violation, which verifies that the callback function's
> types match the prototypes exactly before jumping.
> 
> [    0.857913] CFI failure (target: 0xffffff9334a81820):
> [    0.857977] WARNING: CPU: 3 PID: 35 at kernel/cfi.c:29 __cfi_check_fail+0x50/0x58
> [    0.857985] Modules linked in:
> [    0.858007] CPU: 3 PID: 35 Comm: kworker/3:1 Not tainted 4.19.123-v8-01301-gdbb48f16956e4-dirty #1
> [    0.858015] Hardware name: Raspberry Pi 3 Model B Rev 1.2 (DT)
> [    0.858031] Workqueue: events 0xffffff9334a925c8
> [    0.858046] pstate: 60000005 (nZCv daif -PAN -UAO)
> [    0.858058] pc : __cfi_check_fail+0x50/0x58
> [    0.858070] lr : __cfi_check_fail+0x50/0x58
> [    0.858078] sp : ffffff800814ba90
> [    0.858086] x29: ffffff800814ba90 x28: 000fffffffdfff3d
> [    0.858101] x27: 00000000002000c2 x26: ffffff93355fdb18
> [    0.858116] x25: 0000000000000000 x24: ffffff9334a81820
> [    0.858131] x23: ffffff93357f3580 x22: ffffff9334af1000
> [    0.858146] x21: a79b57e88f8ebc81 x20: ffffff93357f3580
> [    0.858161] x19: ffffff9334a81820 x18: fffffff679769070
> [    0.858175] x17: 0000000000000000 x16: 0000000000000000
> [    0.858190] x15: 0000000000000004 x14: 000000000000003c
> [    0.858205] x13: 0000000000003044 x12: 0000000000000000
> [    0.858220] x11: b57e91cd641bae00 x10: b57e91cd641bae00
> [    0.858235] x9 : b57e91cd641bae00 x8 : b57e91cd641bae00
> [    0.858250] x7 : 0000000000000000 x6 : ffffff933591d4e5
> [    0.858264] x5 : 0000000000000000 x4 : 0000000000000000
> [    0.858279] x3 : ffffff800814b718 x2 : ffffff9334a84818
> [    0.858293] x1 : ffffff9334bba66c x0 : 0000000000000029
> [    0.858308] Call trace:
> [    0.858321]  __cfi_check_fail+0x50/0x58
> [    0.858337]  __cfi_check+0x3ab3c/0x4467c
> [    0.858351]  bcm2835_clk_probe+0x210/0x2dc
> [    0.858369]  platform_drv_probe+0xb0/0xfc
> [    0.858380]  really_probe+0x4a0/0x5a8
> [    0.858391]  driver_probe_device+0x68/0x104
> [    0.858403]  __device_attach_driver+0x100/0x148
> [    0.858418]  bus_for_each_drv+0xb0/0x12c
> [    0.858431]  __device_attach.llvm.17225159516306086099+0xc0/0x168
> [    0.858443]  bus_probe_device+0x44/0xfc
> [    0.858455]  deferred_probe_work_func+0xa0/0xe0
> [    0.858472]  process_one_work+0x210/0x538
> [    0.858485]  worker_thread+0x2e8/0x478
> [    0.858500]  kthread+0x154/0x164
> [    0.858515]  ret_from_fork+0x10/0x18
> 
> To fix this, change the second parameter of all functions void * and use
> a local variable with the correct type so that everything works
> properly. With this, the only use of bcm2835_clk_register is in struct
> bcm2835_clk_desc so we can just remove it and use the type directly.
> 
> Fixes: 56eb3a2ed972 ("clk: bcm2835: remove use of BCM2835_CLOCK_COUNT in driver")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1028
> Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> ---

Applied to clk-next