minix/servers/vm/mem_shared.c

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/* This file implements the methods of shared memory. */
#include <assert.h>
#include "proto.h"
#include "vm.h"
#include "region.h"
#include "glo.h"
/* These functions are static so as to not pollute the
* global namespace, and are accessed through their function
* pointers.
*/
static int shared_unreference(struct phys_region *pr);
static int shared_pagefault(struct vmproc *vmp, struct vir_region *region,
struct phys_region *ph, int write, vfs_callback_t cb, void *state,
int len, int *io);
make vfs & filesystems use failable copying Change the kernel to add features to vircopy and safecopies so that transparent copy fixing won't happen to avoid deadlocks, and such copies fail with EFAULT. Transparently making copying work from filesystems (as normally done by the kernel & VM when copying fails because of missing/readonly memory) is problematic as it can happen that, for file-mapped ranges, that that same filesystem that is blocked on the copy request is needed to satisfy the memory range, leading to deadlock. Dito for VFS itself, if done with a blocking call. This change makes the copying done from a filesystem fail in such cases with EFAULT by VFS adding the CPF_TRY flag to the grants. If a FS call fails with EFAULT, VFS will then request the range to be made available to VM after the FS is unblocked, allowing it to be used to satisfy the range if need be in another VFS thread. Similarly, for datacopies that VFS itself does, it uses the failable vircopy variant and callers use a wrapper that talk to VM if necessary to get the copy to work. . kernel: add CPF_TRY flag to safecopies . kernel: only request writable ranges to VM for the target buffer when copying fails . do copying in VFS TRY-first . some fixes in VM to build SANITYCHECK mode . add regression test for the cases where - a FS system call needs memory mapped in a process that the FS itself must map. - such a range covers more than one file-mapped region. . add 'try' mode to vircopy, physcopy . add flags field to copy kernel call messages . if CP_FLAG_TRY is set, do not transparently try to fix memory ranges . for use by VFS when accessing user buffers to avoid deadlock . remove some obsolete backwards compatability assignments . VFS: let thread scheduling work for VM requests too Allows VFS to make calls to VM while suspending and resuming the currently running thread. Does currently not work for the main thread. . VM: add fix memory range call for use by VFS Change-Id: I295794269cea51a3163519a9cfe5901301d90b32
2014-01-16 14:22:13 +01:00
static int shared_sanitycheck(struct phys_region *pr, const char *file, int line);
static int shared_writable(struct phys_region *pr);
static void shared_delete(struct vir_region *region);
static u32_t shared_regionid(struct vir_region *region);
static int shared_copy(struct vir_region *vr, struct vir_region *newvr);
static int shared_refcount(struct vir_region *vr);
static int shared_pt_flags(struct vir_region *vr);
struct mem_type mem_type_shared = {
.name = "shared memory",
.ev_copy = shared_copy,
.ev_unreference = shared_unreference,
.ev_pagefault = shared_pagefault,
.ev_sanitycheck = shared_sanitycheck,
.ev_delete = shared_delete,
.regionid = shared_regionid,
.refcount = shared_refcount,
.writable = shared_writable,
.pt_flags = shared_pt_flags,
};
static int shared_pt_flags(struct vir_region *vr){
#if defined(__arm__)
return ARM_VM_PTE_CACHED;
#else
return 0;
#endif
}
static int shared_unreference(struct phys_region *pr)
{
return mem_type_anon.ev_unreference(pr);
}
static int getsrc(struct vir_region *region,
struct vmproc **vmp, struct vir_region **r)
{
int srcproc;
if(region->def_memtype != &mem_type_shared) {
printf("shared region hasn't shared type but %s.\n",
region->def_memtype->name);
return EINVAL;
}
if(!region->param.shared.ep || !region->param.shared.vaddr) {
printf("shared region has not defined source region.\n");
util_stacktrace();
return EINVAL;
}
if(vm_isokendpt((endpoint_t) region->param.shared.ep, &srcproc) != OK) {
printf("VM: shared memory with missing source process.\n");
util_stacktrace();
return EINVAL;
}
*vmp = &vmproc[srcproc];
if(!(*r=map_lookup(*vmp, region->param.shared.vaddr, NULL))) {
printf("VM: shared memory with missing vaddr 0x%lx.\n",
region->param.shared.vaddr);
return EINVAL;
}
if((*r)->def_memtype != &mem_type_anon) {
printf("source region hasn't anon type but %s.\n",
(*r)->def_memtype->name);
return EINVAL;
}
if(region->param.shared.id != (*r)->id) {
printf("source region has no matching id\n");
return EINVAL;
}
return OK;
}
static u32_t shared_regionid(struct vir_region *vr)
{
struct vir_region *src_region;
struct vmproc *src_vmp;
if(getsrc(vr, &src_vmp, &src_region) != OK)
return 0;
return src_region->id;
}
static void shared_delete(struct vir_region *region)
{
struct vir_region *src_region;
struct vmproc *src_vmp;
if(getsrc(region, &src_vmp, &src_region) != OK)
return;
assert(src_region->remaps > 0);
src_region->remaps--;
}
static int shared_pagefault(struct vmproc *vmp, struct vir_region *region,
struct phys_region *ph, int write, vfs_callback_t cb,
void *state, int statelen, int *io)
{
struct vir_region *src_region;
struct vmproc *src_vmp;
struct phys_region *pr;
if(getsrc(region, &src_vmp, &src_region) != OK) {
return EINVAL;
}
assert(ph->ph->phys == MAP_NONE);
pb_free(ph->ph);
if(!(pr = physblock_get(src_region, ph->offset))) {
int r;
if((r=map_pf(src_vmp, src_region, ph->offset, write,
NULL, NULL, 0, io)) != OK)
return r;
if(!(pr = physblock_get(src_region, ph->offset))) {
panic("missing region after pagefault handling");
}
}
pb_link(ph, pr->ph, ph->offset, region);
return OK;
}
make vfs & filesystems use failable copying Change the kernel to add features to vircopy and safecopies so that transparent copy fixing won't happen to avoid deadlocks, and such copies fail with EFAULT. Transparently making copying work from filesystems (as normally done by the kernel & VM when copying fails because of missing/readonly memory) is problematic as it can happen that, for file-mapped ranges, that that same filesystem that is blocked on the copy request is needed to satisfy the memory range, leading to deadlock. Dito for VFS itself, if done with a blocking call. This change makes the copying done from a filesystem fail in such cases with EFAULT by VFS adding the CPF_TRY flag to the grants. If a FS call fails with EFAULT, VFS will then request the range to be made available to VM after the FS is unblocked, allowing it to be used to satisfy the range if need be in another VFS thread. Similarly, for datacopies that VFS itself does, it uses the failable vircopy variant and callers use a wrapper that talk to VM if necessary to get the copy to work. . kernel: add CPF_TRY flag to safecopies . kernel: only request writable ranges to VM for the target buffer when copying fails . do copying in VFS TRY-first . some fixes in VM to build SANITYCHECK mode . add regression test for the cases where - a FS system call needs memory mapped in a process that the FS itself must map. - such a range covers more than one file-mapped region. . add 'try' mode to vircopy, physcopy . add flags field to copy kernel call messages . if CP_FLAG_TRY is set, do not transparently try to fix memory ranges . for use by VFS when accessing user buffers to avoid deadlock . remove some obsolete backwards compatability assignments . VFS: let thread scheduling work for VM requests too Allows VFS to make calls to VM while suspending and resuming the currently running thread. Does currently not work for the main thread. . VM: add fix memory range call for use by VFS Change-Id: I295794269cea51a3163519a9cfe5901301d90b32
2014-01-16 14:22:13 +01:00
static int shared_sanitycheck(struct phys_region *pr, const char *file, int line)
{
return OK;
}
static int shared_writable(struct phys_region *pr)
{
assert(pr->ph->refcount > 0);
return pr->ph->phys != MAP_NONE;
}
void shared_setsource(struct vir_region *vr, endpoint_t ep,
struct vir_region *src_vr)
{
struct vmproc *vmp;
struct vir_region *srcvr;
int id = src_vr->id;
vir_bytes vaddr = src_vr->vaddr;
assert(vr->def_memtype == &mem_type_shared);
if(!ep || !vaddr || !id) {
printf("VM: shared_setsource: zero ep/vaddr/id - ignoring\n");
return;
}
vr->param.shared.ep = ep;
vr->param.shared.vaddr = vaddr;
vr->param.shared.id = id;
if(getsrc(vr, &vmp, &srcvr) != OK)
panic("initial getsrc failed");
assert(srcvr == src_vr);
srcvr->remaps++;
}
static int shared_copy(struct vir_region *vr, struct vir_region *newvr)
{
struct vmproc *vmp;
struct vir_region *srcvr;
if(getsrc(vr, &vmp, &srcvr) != OK)
panic("copy: original getsrc failed");
shared_setsource(newvr, vr->param.shared.ep, srcvr);
return OK;
}
static int shared_refcount(struct vir_region *vr)
{
return 1 + vr->remaps;
}