Commit 3d3539018d2c ("mm: create the new vm_fault_t type") in mainline
5.1-rc1 changed the definition of vm_fault_t type to unsigned to catch
vm_operations_struct::fault handlers which still have int as return value.
LinuxDriverFault() in vmmon module is one of those.
As handler return type was changed by commit 1c8f422059ae ("mm: change
return type to vm_fault_t") in 4.17-rc1, make LinuxDriverFault() always
return vm_fault_t and define vm_fault_t as int when building against
a pre-4.17 kernel.
Commit 736706bee329 ("get rid of legacy 'get_ds()' function") in v5.1-rc1
removed get_ds() helper. As this helper always returned KERNEL_DS on x86_64
since the architecture was introduced (and even on i386, it did so since
v2.1.0), simply use KERNEL_DS regardless of kernel version.
Since commit 96d4f267e40f ("Remove 'type' argument from access_ok()
function") in v5.0-rc1, the type argument of access_ok() was dropped.
The same commit also dropped macros VERIFY_READ and VERIFY_WRITE so check
for their existence on pre-5.0 kernels to allow build against kernels with
this change backported.
The do_gettimeofday() helper was removed by commit e4b92b108c6c
("timekeeping: remove obsolete time accessors") in v5.0-rc1. Bring it back
for users in vmmon-only/linux/hostif.c.
This feels like a quick and clumsy band aid to allow build with post-4.20
kernels. On a closer look, the whole gymnastics around uptimeState and
HostIFReadUptimeWork() with jiffies and wall time checking and correcting
each other seems to be a workaround for an absence of high resolution
monotonic time. Considering ktime_get_ts64() is available since 3.17 and
before that, ktime_get_ts() since 2.6.17, perhaps the time has come to
clean all this machinery up. But something like this would be beyond the
scope of this repository.
Since commit ca79b0c211af ("mm: convert totalram_pages and totalhigh_pages
variables to atomic") in v5.0-rc1, totalram_pages() is an accessor function
and the actual variable is an atomic.
Commit 11c5ad0ec441 ("eventpoll: switch to ->poll_mask") in v4.18-rc1, made
eventpoll switch from ->poll() to ->poll_mask(), resulting in a null
pointer dereference as vmmon calls the callback directly without checking
its availability.
Rather than calling the callback directly (which would result in null
pointer dereference), use vfs_poll() wrapper. As this wrapper is only
available since 4.18-rc1 cycle as well, provide a copy to use when building
against older kernels.
Note: even if the commit revealing the problem was reverted in 4.18-rc3
(and is unlikely to go back in the same form) so that vmmon no longer
crashes with 4.18 kernel, calling the callback without a check is a bad
practice so let's keep the patch in place.
Function declared with __attribute__((always_inline)) should also be
declared as inline, otherwise gcc issues a warning "always_inline function
might not be inlinable". It's just cosmetic but getting rid of known
harmless warnings makes it easier to spot actual problems. Use the
__always_inline macro for LinuxDriverSyncReadTSCs() as this is how always
inline functions should be declared in kernel code.
Michal Kubecek