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drm-shim: Support kernels with >4k pages

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mmap requires its offset is page aligned, but the current code only
guarantees 4k alignment, causing drm-shim to break badly on kernels with
>4k page sizes. This fixes drm-shim on my Apple M1, running bare metal
Linux with 16k pages. It probably also fixes exotic PowerPC systems with
64k pages.

Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Zoltan Boszormenyi <zboszor@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
Cc: mesa-stable
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12347>
This commit is contained in:
Alyssa Rosenzweig 2021-08-12 18:54:49 +00:00 committed by Marge Bot
parent 5f2dbd45f2
commit 38f39cc1e2
1 changed files with 21 additions and 2 deletions
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23
src/drm-shim/device.c
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@ -57,6 +57,8 @@ memfd_create(const char *name, unsigned int flags)
/* Global state for the shim shared between libc, core, and driver. */
struct shim_device shim_device;
long shim_page_size;
static uint32_t
uint_key_hash(const void *key)
{
@ -88,7 +90,21 @@ drm_shim_device_init(void)
ASSERTED int ret = ftruncate(shim_device.mem_fd, SHIM_MEM_SIZE);
assert(ret == 0);
util_vma_heap_init(&shim_device.mem_heap, 4096, SHIM_MEM_SIZE - 4096);
/* The man page for mmap() says
*
* offset must be a multiple of the page size as returned by
* sysconf(_SC_PAGE_SIZE).
*
* Depending on the configuration of the kernel, this may not be 4096. Get
* this page size once and use it as the page size throughout, ensuring that
* are offsets are page-size aligned as required. Otherwise, mmap will fail
* with EINVAL.
*/
shim_page_size = sysconf(_SC_PAGE_SIZE);
util_vma_heap_init(&shim_device.mem_heap, shim_page_size,
SHIM_MEM_SIZE - shim_page_size);
drm_shim_driver_init();
}
@ -270,7 +286,7 @@ drm_shim_bo_init(struct shim_bo *bo, size_t size)
{
mtx_lock(&shim_device.mem_lock);
bo->mem_addr = util_vma_heap_alloc(&shim_device.mem_heap, size, 4096);
bo->mem_addr = util_vma_heap_alloc(&shim_device.mem_heap, size, shim_page_size);
mtx_unlock(&shim_device.mem_lock);
assert(bo->mem_addr);
@ -361,5 +377,8 @@ drm_shim_mmap(struct shim_fd *shim_fd, size_t length, int prot, int flags,
{
struct shim_bo *bo = (void *)(uintptr_t)offset;
/* The offset we pass to mmap must be aligned to the page size */
assert((bo->mem_addr & (shim_page_size - 1)) == 0);
return mmap(NULL, length, prot, flags, shim_device.mem_fd, bo->mem_addr);
}