On Tue, 20 Jan 2015, Javier Martinez Canillas wrote:
> Hello Lee,
>
> On 01/20/2015 05:36 PM, Lee Jones wrote:
> >> >
> >> > Is this safe? Are you sure it's okay to provide an interface from
> >> > userspace to read (kernel?) memory?
> >> >
> >>
> >> This interface is not to read any kernel memory but only the memory mapped
> >> I/O region for the Low Pin Count (LPC) bus. So user-space only can choose
> >> and offset and a number of bytes using the CROS_EC_DEV_IOCRDMEM ioctl cmd
> >> which uses the following structure as argument:
> >>
> >> /*
> >> * @offset: within EC_LPC_ADDR_MEMMAP region
> >> * @bytes: number of bytes to read. zero means "read a string" (including '\0')
> >> * (at most only EC_MEMMAP_SIZE bytes can be read)
> >> * @buffer: where to store the result
> >> * ioctl returns the number of bytes read, negative on error
> >> */
> >> struct cros_ec_readmem {
> >> uint32_t offset;
> >> uint32_t bytes;
> >> uint8_t buffer[EC_MEMMAP_SIZE];
> >> };
> >>
> >> The cros_ec_lpc_readmem() handler that the function pointer is set only
> >> reads bytes from EC_LPC_ADDR_MEMMAP + offset if offset < EC_MEMMAP_SIZE
> >> and the data is copied to the user-space buffer from the structure passed
> >> as argument with copy_to_user().
> >>
> >> So in that sense is similar to the spidev or i2c-dev interfaces that are
> >> used to access these buses from user-space.
> >
> > Very well. The purpose of my question was to be provocative and to
> > make you think about the interface. As long as you're sure it can't
> > be abused, then I'm happy.
> >
>
> Ok, thanks a lot. Does it mean I've your Acked-by for this patch too?
Yes: Acked-by: Lee Jones <lee.jones@xxxxxxxxxx>
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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