We've developed a PCIDriverKit driver for the capture card on macOS and have identified an issue: CreateMemoryDescriptorFromClient can only read data from the user space to the driver, but cannot write data back to the user.
typedef struct _MWCAP_EDID_DATA {
uint64_t size;
uint64_t uaddr;
} MWCAP_EDID_DATA;
// App
size_t xxx::GetEdid(void *buff, size_t size)
{
MWCAP_EDID_DATA edid;
edid.size = size;
edid.uaddr = (uint64_t)buff;
kr = IOConnectCallStructMethod(
connect,
kUserGetEdid,
&edid,
sizeof(MWCAP_EDID_DATA),
NULL,
NULL
);
// kr is 0. But However, the data in the buffer remains unchanged;
// it does not reflect the EDID copied from the DEXT.
return size;
}
// Driver
MWCAP_EDID_DATA *edid = (MWCAP_EDID_DATA *)input;
IOMemoryDescriptor *user_buf_mem = NULL;
IOAddressSegment segment;
segment.address = edid->uaddr;
segment.length = edid->size;
// We have verified that the values in edid->uaddr and edid->size are consistent with what was set by the application.
ret = CreateMemoryDescriptorFromClient(kIOMemoryDirectionOutIn, 1, &segment, &user_buf_mem);
if (ret != kIOReturnSuccess) {
os_log(OS_LOG_DEFAULT, "Failed to create memdesc with error: 0x%08x", ret);
break;
}
IOMemoryMap* user_buf_map = nullptr;
ret = user_buf_mem->CreateMapping(0, 0, 0, 0, 0, &user_buf_map);
if (ret != kIOReturnSuccess) {
os_log(OS_LOG_DEFAULT, "Failed to create mapping with error: 0x%08x", ret);
OSSafeReleaseNULL(user_buf_mem);
break;
}
// ... fill the user_buf_map with edid data ...
// For example:
// memcpy(user_buf_map->GetAddress(), source_edid_data, edid->size);
// At this point we have also verified the data in user_buf_map->GetAddress(), which matches our expectations.
OSSafeReleaseNULL(user_buf_map);
OSSafeReleaseNULL(user_buf_mem);
Please help take a look, thank you!
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