Re: drivers/irqchip/irq-apple-aic.c:941 aic_of_ic_init() error: uninitialized symbol 'off'.

Marc Zyngier
2022-06-06T11:16:32Z

On Mon, 06 Jun 2022 12:08:03 +0100,
Dan Carpenter <dan.carpenter@oracle.com> wrote:
>
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 8ab2afa23bd197df47819a87f0265c0ac95c5b6a
> commit: dc97fd6fec009957e81026055fc99a03877ff3b8 irqchip/apple-aic: Dynamically compute register offsets
> config: arm64-randconfig-m031-20220530 (https://download.01.org/0day-ci/archive/20220601/202206010439.LRgjym7t-lkp@intel.com/config)
> compiler: aarch64-linux-gcc (GCC) 11.3.0
>
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>
> New smatch warnings:
> drivers/irqchip/irq-apple-aic.c:941 aic_of_ic_init() error: uninitialized symbol 'off'.
>
> vim +/off +941 drivers/irqchip/irq-apple-aic.c
>
> 76cde26394114f Hector Martin 2021-01-21 900 static int __init aic_of_ic_init(struct device_node *node, struct device_node *parent)
> 76cde26394114f Hector Martin 2021-01-21 901 {
> 76cde26394114f Hector Martin 2021-01-21 902 int i;
> dc97fd6fec0099 Hector Martin 2022-03-10 903 u32 off;
> 76cde26394114f Hector Martin 2021-01-21 904 void __iomem *regs;
> 76cde26394114f Hector Martin 2021-01-21 905 struct aic_irq_chip *irqc;
> 2cf68211664acd Hector Martin 2022-03-10 906 const struct of_device_id *match;
> 76cde26394114f Hector Martin 2021-01-21 907
> 76cde26394114f Hector Martin 2021-01-21 908 regs = of_iomap(node, 0);
> 76cde26394114f Hector Martin 2021-01-21 909 if (WARN_ON(!regs))
> 76cde26394114f Hector Martin 2021-01-21 910 return -EIO;
> 76cde26394114f Hector Martin 2021-01-21 911
> 76cde26394114f Hector Martin 2021-01-21 912 irqc = kzalloc(sizeof(*irqc), GFP_KERNEL);
> 76cde26394114f Hector Martin 2021-01-21 913 if (!irqc)
> 76cde26394114f Hector Martin 2021-01-21 914 return -ENOMEM;
> 76cde26394114f Hector Martin 2021-01-21 915
> 76cde26394114f Hector Martin 2021-01-21 916 irqc->base = regs;
> 76cde26394114f Hector Martin 2021-01-21 917
> 2cf68211664acd Hector Martin 2022-03-10 918 match = of_match_node(aic_info_match, node);
> 2cf68211664acd Hector Martin 2022-03-10 919 if (!match)
> 2cf68211664acd Hector Martin 2022-03-10 920 return -ENODEV;
> 2cf68211664acd Hector Martin 2022-03-10 921
> 2cf68211664acd Hector Martin 2022-03-10 922 irqc->info = *(struct aic_info *)match->data;
> 2cf68211664acd Hector Martin 2022-03-10 923
> 2cf68211664acd Hector Martin 2022-03-10 924 aic_irqc = irqc;
> 2cf68211664acd Hector Martin 2022-03-10 925
> dc97fd6fec0099 Hector Martin 2022-03-10 926 switch (irqc->info.version) {
> dc97fd6fec0099 Hector Martin 2022-03-10 927 case 1: {
> dc97fd6fec0099 Hector Martin 2022-03-10 928 u32 info;
> dc97fd6fec0099 Hector Martin 2022-03-10 929
> 76cde26394114f Hector Martin 2021-01-21 930 info = aic_ic_read(irqc, AIC_INFO);
> 7c841f5f6fa3f9 Hector Martin 2022-03-10 931 irqc->nr_irq = FIELD_GET(AIC_INFO_NR_IRQ, info);
> dc97fd6fec0099 Hector Martin 2022-03-10 932 irqc->max_irq = AIC_MAX_IRQ;
> dc97fd6fec0099 Hector Martin 2022-03-10 933
> dc97fd6fec0099 Hector Martin 2022-03-10 934 off = irqc->info.target_cpu;
> dc97fd6fec0099 Hector Martin 2022-03-10 935 off += sizeof(u32) * irqc->max_irq; /* TARGET_CPU */
> dc97fd6fec0099 Hector Martin 2022-03-10 936
> dc97fd6fec0099 Hector Martin 2022-03-10 937 break;
>
> "off" uninitialized if irqc->info.version != 1.

Which is pretty much impossible by construction, as as of this
particular commit, all the possible implementations have version == 1.

Subsequent patches do add cases where version == 2, and that gets
covered too.

So unless I'm missing something obvious, there is no bug here.

Thanks,

M.

--
Without deviation from the norm, progress is not possible.