Messages in this thread | | | From | (Krzysztof Hałasa) | Date | Wed, 27 May 2015 08:45:38 +0200 | Subject | Re: [PATCH] ARM: cns3xxx: pci: avoid potential stack overflow |
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Arnd Bergmann <arnd@arndb.de> writes:
> The cns3xxx_pcie_hw_init function uses excessive kernel > stack space because of a hack that puts a fake struct > pci_sys_data and struct pci_bus on the stack in order to > call the generic pci_bus_read_config accessors, which causes > a warning in ARM allmodconfig builds: > > arch/arm/mach-cns3xxx/pcie.c:266:1: warning: the frame size of 1080 bytes is larger than 1024 bytes > > This rewrites the code in question to use a private > implementation of the config space access for the same > purpose, getting rid of the local variables and the > warning in the process. As part of this, we have to > use an open-coded version of pci_bus_find_capability(), > which unfortunately complicates the implementation.
Wouldn't it be better to simply use static structs for this purpose? The hack isn't pretty, though.
> + regs = cnspci->cfg0_regs + (PCI_DEVFN(1, 0) << 12); > +
Some comment about would be helpful. Such as this:
> - bus.number = 1; /* directly connected PCIe device */ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> + pos = cns3xxx_pci_raw_read_config(regs, PCI_CAPABILITY_LIST, 1); > + while (cns3xxx_pci_raw_read_config(regs, pos, 1) != PCI_CAP_ID_EXP) > + pos = cns3xxx_pci_raw_read_config(regs, pos + PCI_CAP_LIST_NEXT, 1); > +
I wonder if this can fail (i.e., no PCI_CAP_ID_EXP capability).
> + dc = cns3xxx_pci_raw_read_config(regs, pos + PCI_EXP_DEVCTL, 2); > + dc &= ~(0x3 << 12); /* Clear Device Control Register [14:12] */ > + cns3xxx_pci_raw_write_config(regs, pos + PCI_EXP_DEVCTL, 2, dc); > + dc = cns3xxx_pci_raw_read_config(regs, pos + PCI_EXP_DEVCTL, 2); > + if (!(dc & (0x3 << 12))) > + pr_info("PCIe: Set Device Max_Read_Request_Size to 128 byte\n"); > +
This seems to revert 367dc4b75f4349d5363bc3ebdc030939db944786. Why do you want to do it? -- Krzysztof Halasa
Research Institute for Automation and Measurements PIAP Al. Jerozolimskie 202, 02-486 Warsaw, Poland
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