Messages in this thread | | | From | Daniel Gutson <> | Date | Thu, 30 Jul 2020 11:18:20 -0300 | Subject | Re: [PATCH] Module argument to control whether intel-spi-pci attempts to turn the SPI flash chip writeable |
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On Thu, Jul 30, 2020 at 11:09 AM Arnd Bergmann <arnd@arndb.de> wrote: > > On Thu, Jul 30, 2020 at 2:21 PM Daniel Gutson <daniel@eclypsium.com> wrote: > > El jue., 30 jul. 2020 2:31 a. m., Greg Kroah-Hartman <gregkh@linuxfoundation.org> escribió: > >> > >> Again, module parameters are working on a per-chunk-of-code basis, while > >> you want to work on a per-device basis, > > > > > > I think there is a misunderstanding. What I want is to control (turn on or off) is a very specific code snippet that provides the "functionality" of trying to turn the chip writable. The rest of the device driver is fine. > > I assume that the one that doesn't understand is me. > > > > I looked at the source code again and found that the existing module > parameter applies to both the platform and pci device front-ends, both > of which go through > > /* Prevent writes if not explicitly enabled */ > if (!ispi->writeable || !writeable) > ispi->nor.mtd.flags &= ~MTD_WRITEABLE; >
I think you missed https://elixir.bootlin.com/linux/latest/source/drivers/mtd/spi-nor/controllers/intel-spi-pci.c#L44
/* Try to make the chip read/write */ pci_read_config_dword(pdev, BCR, &bcr); if (!(bcr & BCR_WPD)) { bcr |= BCR_WPD; pci_write_config_dword(pdev, BCR, bcr); pci_read_config_dword(pdev, BCR, &bcr); }
in the probe function, and is executed always and unconditionally.
/* Try to make the chip read/write */ pci_read_config_dword(pdev, BCR, &bcr); if (!(bcr & BCR_WPD)) { bcr |= BCR_WPD; pci_write_config_dword(pdev, BCR, bcr); pci_read_config_dword(pdev, BCR, &bcr); }
> Setting the PCI device writable in hardware makes it possible to > actually write to it *only* if the module parameter is also set to '1'. > One might disagree with that design, but I don't think your patch > would make it any better, it just means one would have to set > two module parameters instead of one. > > Arnd
-- Daniel Gutson Argentina Site Director Enginieering Director Eclypsium
Below The Surface: Get the latest threat research and insights on firmware and supply chain threats from the research team at Eclypsium. https://eclypsium.com/research/#threatreport
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