Re: [PATCH v8 1/3] devres: provide devm_krealloc()
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Date: 2020-08-21 11:04:14
Also in:
linux-iio, lkml
On Fri, Aug 21, 2020 at 01:51:19PM +0300, Andy Shevchenko wrote:
On Fri, Aug 21, 2020 at 10:59:19AM +0200, Bartosz Golaszewski wrote:quoted
On Fri, Aug 21, 2020 at 10:35 AM Andy Shevchenko [off-list ref] wrote:quoted
On Thu, Aug 20, 2020 at 08:51:08PM +0200, Bartosz Golaszewski wrote:
...
quoted
quoted
quoted
+static struct devres *to_devres(void *data) +{ + return data - ALIGN(sizeof(struct devres), ARCH_KMALLOC_MINALIGN); +} + +static size_t devres_data_size(size_t total_size) +{ + return total_size - ALIGN(sizeof(struct devres), ARCH_KMALLOC_MINALIGN); +}
quoted
The data pointer in struct devres is defined as: u8 __aligned(ARCH_KMALLOC_MINALIGN) data[]; And this value (assigned the value of ARCH_DMA_MINALIGN) varies from one arch to another. I wasn't really sure if offsetof() would work for every case so I went with something very explicit.I have checked with a small program simulating to_devres() with your variant, offsetof() and container_of(). The result is this: if MINALIGN < sizeof(long) and since struct is unpacked the offsetof(), and thus container_of(), gives correct result, while ALIGN() approach mistakenly moves pointer too back.
...
I think you need to change this to use container_of() and offsetof().
To be clear, there is probably no real problem, except unlikely possible MINALIGN=4 on 64-bit arch, but for sake of the correctness. -- With Best Regards, Andy Shevchenko _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel