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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3] x86/mm: Add mem access rights to NPT
> On Jul 2, 2018, at 8:42 AM, Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx> wrote:
>
> From: Isaila Alexandru <aisaila@xxxxxxxxxxxxxxx>
>
> This patch adds access rights for the NPT pages. The access rights are
> saved in a radix tree with the root saved in p2m_domain. The rights are
> manipulated through p2m_set_access()
> and p2m_get_access() functions.
> The patch follows the ept logic.
This description needs to be much more complete. Something like this:
---
This patch adds access control for NPT mode.
There aren’t enough extra bits to store the access rights in the NPT p2m table,
so we add a radix tree to store the rights. For efficiency, remove entries
which match the default permissions rather than continuing to store them.
Modify p2m-pt.c:p2m_type_to_flags() to mirror the ept version: taking an
access, and removing / adding RW or NX flags as appropriate.
---
>
> Note: It was tested with xen-access write
>
> Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
>
> ---
> Changes since V2:
> - Delete blak line
> - Add return if p2m_access_rwx = a
> - Delete the comment from p2m_pt_get_entry()
> - Moved radix_tree_init() to arch_monitor_init_domain().
> ---
> xen/arch/x86/mm/mem_access.c | 3 ++
> xen/arch/x86/mm/p2m-pt.c | 109 ++++++++++++++++++++++++++++++++++-----
> xen/arch/x86/mm/p2m.c | 6 +++
> xen/arch/x86/monitor.c | 13 +++++
> xen/include/asm-x86/mem_access.h | 2 +-
> xen/include/asm-x86/p2m.h | 6 +++
> 6 files changed, 124 insertions(+), 15 deletions(-)
>
> diff --git a/xen/arch/x86/mm/mem_access.c b/xen/arch/x86/mm/mem_access.c
> index c0cd017..d78c82c 100644
> --- a/xen/arch/x86/mm/mem_access.c
> +++ b/xen/arch/x86/mm/mem_access.c
> @@ -221,7 +221,10 @@ bool p2m_mem_access_check(paddr_t gpa, unsigned long gla,
> {
> req->u.mem_access.flags |= MEM_ACCESS_GLA_VALID;
> req->u.mem_access.gla = gla;
> + }
>
> + if ( npfec.gla_valid || cpu_has_svm )
> + {
I can’t immediately tell what this is about, which means it needs a comment.
It may also be (depending on why this is here) that “cpu_has_svm” makes this
more fragile — if this is really about having a radix tree, for instance, then
you should probably check for a radix tree.
> if ( npfec.kind == npfec_kind_with_gla )
> req->u.mem_access.flags |= MEM_ACCESS_FAULT_WITH_GLA;
> else if ( npfec.kind == npfec_kind_in_gpt )
> diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
> index b8c5d2e..4330d1f 100644
> --- a/xen/arch/x86/mm/p2m-pt.c
> +++ b/xen/arch/x86/mm/p2m-pt.c
> @@ -68,7 +68,8 @@
> static unsigned long p2m_type_to_flags(const struct p2m_domain *p2m,
> p2m_type_t t,
> mfn_t mfn,
> - unsigned int level)
> + unsigned int level,
> + p2m_access_t access)
> {
> unsigned long flags;
> /*
> @@ -87,23 +88,27 @@ static unsigned long p2m_type_to_flags(const struct
> p2m_domain *p2m,
> case p2m_ram_paged:
> case p2m_ram_paging_in:
> default:
> - return flags | _PAGE_NX_BIT;
> + flags |= P2M_BASE_FLAGS | _PAGE_NX_BIT;
> + break;
> case p2m_grant_map_ro:
> return flags | P2M_BASE_FLAGS | _PAGE_NX_BIT;
> case p2m_ioreq_server:
> flags |= P2M_BASE_FLAGS | _PAGE_RW | _PAGE_NX_BIT;
> if ( p2m->ioreq.flags & XEN_DMOP_IOREQ_MEM_ACCESS_WRITE )
> - return flags & ~_PAGE_RW;
> - return flags;
> + flags &= ~_PAGE_RW;
> + break;
> case p2m_ram_ro:
> case p2m_ram_logdirty:
> case p2m_ram_shared:
> - return flags | P2M_BASE_FLAGS;
> + flags |= P2M_BASE_FLAGS;
> + break;
> case p2m_ram_rw:
> - return flags | P2M_BASE_FLAGS | _PAGE_RW;
> + flags |= P2M_BASE_FLAGS | _PAGE_RW;
> + break;
> case p2m_grant_map_rw:
> case p2m_map_foreign:
> - return flags | P2M_BASE_FLAGS | _PAGE_RW | _PAGE_NX_BIT;
> + flags |= P2M_BASE_FLAGS | _PAGE_RW | _PAGE_NX_BIT;
> + break;
> case p2m_mmio_direct:
> if ( !rangeset_contains_singleton(mmio_ro_ranges, mfn_x(mfn)) )
> flags |= _PAGE_RW;
> @@ -112,8 +117,37 @@ static unsigned long p2m_type_to_flags(const struct
> p2m_domain *p2m,
> flags |= _PAGE_PWT;
> ASSERT(!level);
> }
> - return flags | P2M_BASE_FLAGS | _PAGE_PCD;
> + flags |= P2M_BASE_FLAGS | _PAGE_PCD;
> + break;
> + }
I think you want a blank line here.
> + switch ( access )
> + {
> + case p2m_access_r:
> + case p2m_access_w:
> + flags |= _PAGE_NX_BIT;
> + flags &= ~_PAGE_RW;
> + break;
> + case p2m_access_rw:
> + flags |= _PAGE_NX_BIT;
> + break;
> + case p2m_access_n:
> + case p2m_access_n2rwx:
> + flags |= _PAGE_NX_BIT;
> + flags &= ~_PAGE_RW;
> + break;
> + case p2m_access_rx:
> + case p2m_access_wx:
> + case p2m_access_rx2rw:
> + flags &= ~(_PAGE_NX_BIT | _PAGE_RW);
This looks like a mistake — this will unconditionally enable execution, even if
the underlying p2m type forbids it. ept_p2m_type_to_flags() doesn’t do that.
> + break;
> + case p2m_access_x:
> + flags &= ~_PAGE_RW;
> + break;
> + case p2m_access_rwx:
> + default:
> + break;
> }
I think you want another blank line here too.
Also, this doesn’t seem to capture the ‘r’ part of the equation — shouldn’t
p2m_access_n end up with a not-present p2m entry?
> + return flags;
> }
>
>
> @@ -174,6 +208,44 @@ static void p2m_add_iommu_flags(l1_pgentry_t *p2m_entry,
> l1e_add_flags(*p2m_entry, iommu_nlevel_to_flags(nlevel, flags));
> }
>
> +static p2m_access_t p2m_get_access(struct p2m_domain *p2m, unsigned long gfn)
> +{
> + void *ptr;
> +
> + if ( !p2m->mem_access_settings )
> + return p2m_access_rwx;
> +
> + ptr = radix_tree_lookup(p2m->mem_access_settings, gfn);
> + if ( !ptr )
> + return p2m_access_rwx;
> + else
> + return radix_tree_ptr_to_int(ptr);
> +}
> +
> +static void p2m_set_access(struct p2m_domain *p2m, unsigned long gfn,
> + p2m_access_t a)
> +{
> + int rc;
> +
> + if ( !p2m->mem_access_settings )
> + return;
> +
> + if ( p2m_access_rwx == a )
> + {
> + radix_tree_delete(p2m->mem_access_settings, gfn);
> + return;
> + }
> +
> + rc = radix_tree_insert(p2m->mem_access_settings, gfn,
> + radix_tree_int_to_ptr(a));
> + if ( rc == -EEXIST )
> + /* If a setting already exists, change it to the new one. */
> + radix_tree_replace_slot(
> + radix_tree_lookup_slot(
> + p2m->mem_access_settings, gfn),
> + radix_tree_int_to_ptr(a));
> +}
> +
> /* Returns: 0 for success, -errno for failure */
> static int
> p2m_next_level(struct p2m_domain *p2m, void **table,
> @@ -201,6 +273,7 @@ p2m_next_level(struct p2m_domain *p2m, void **table,
> new_entry = l1e_from_mfn(mfn, P2M_BASE_FLAGS | _PAGE_RW);
>
> p2m_add_iommu_flags(&new_entry, level,
> IOMMUF_readable|IOMMUF_writable);
> + p2m_set_access(p2m, gfn, p2m->default_access);
> p2m->write_p2m_entry(p2m, gfn, p2m_entry, new_entry, level + 1);
> }
> else if ( flags & _PAGE_PSE )
> @@ -249,6 +322,7 @@ p2m_next_level(struct p2m_domain *p2m, void **table,
> {
> new_entry = l1e_from_pfn(pfn | (i << ((level - 1) *
> PAGETABLE_ORDER)),
> flags);
> + p2m_set_access(p2m, gfn, p2m->default_access);
> p2m->write_p2m_entry(p2m, gfn, l1_entry + i, new_entry, level);
> }
>
> @@ -256,6 +330,7 @@ p2m_next_level(struct p2m_domain *p2m, void **table,
>
> new_entry = l1e_from_mfn(mfn, P2M_BASE_FLAGS | _PAGE_RW);
> p2m_add_iommu_flags(&new_entry, level,
> IOMMUF_readable|IOMMUF_writable);
> + p2m_set_access(p2m, gfn, p2m->default_access);
> p2m->write_p2m_entry(p2m, gfn, p2m_entry, new_entry, level + 1);
> }
> else
> @@ -420,8 +495,9 @@ static int do_recalc(struct p2m_domain *p2m, unsigned
> long gfn)
> if ( nt != ot )
> {
> unsigned long mfn = l1e_get_pfn(e);
> + p2m_access_t a = p2m_get_access(p2m, gfn);
> unsigned long flags = p2m_type_to_flags(p2m, nt,
> - _mfn(mfn), level);
> + _mfn(mfn), level, a);
>
> if ( level )
> {
> @@ -569,13 +645,14 @@ p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_,
> mfn_t mfn,
> ASSERT(!mfn_valid(mfn) || p2mt != p2m_mmio_direct);
> l3e_content = mfn_valid(mfn) || p2m_allows_invalid_mfn(p2mt)
> ? p2m_l3e_from_pfn(mfn_x(mfn),
> - p2m_type_to_flags(p2m, p2mt, mfn, 2))
> + p2m_type_to_flags(p2m, p2mt, mfn, 2, p2ma))
> : l3e_empty();
> entry_content.l1 = l3e_content.l3;
>
> if ( entry_content.l1 != 0 )
> p2m_add_iommu_flags(&entry_content, 0, iommu_pte_flags);
>
> + p2m_set_access(p2m, gfn, p2ma);
> p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 3);
> /* NB: paging_write_p2m_entry() handles tlb flushes properly */
> }
> @@ -608,7 +685,7 @@ p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_,
> mfn_t mfn,
>
> if ( mfn_valid(mfn) || p2m_allows_invalid_mfn(p2mt) )
> entry_content = p2m_l1e_from_pfn(mfn_x(mfn),
> - p2m_type_to_flags(p2m, p2mt, mfn,
> 0));
> + p2m_type_to_flags(p2m, p2mt, mfn,
> 0, p2ma));
> else
> entry_content = l1e_empty();
>
> @@ -630,6 +707,7 @@ p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_,
> mfn_t mfn,
> p2m->ioreq.entry_count--;
> }
>
> + p2m_set_access(p2m, gfn, p2ma);
> /* level 1 entry */
> p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 1);
> /* NB: paging_write_p2m_entry() handles tlb flushes properly */
> @@ -661,13 +739,14 @@ p2m_pt_set_entry(struct p2m_domain *p2m, gfn_t gfn_,
> mfn_t mfn,
> ASSERT(!mfn_valid(mfn) || p2mt != p2m_mmio_direct);
> l2e_content = mfn_valid(mfn) || p2m_allows_invalid_mfn(p2mt)
> ? p2m_l2e_from_pfn(mfn_x(mfn),
> - p2m_type_to_flags(p2m, p2mt, mfn, 1))
> + p2m_type_to_flags(p2m, p2mt, mfn, 1, p2ma))
> : l2e_empty();
> entry_content.l1 = l2e_content.l2;
>
> if ( entry_content.l1 != 0 )
> p2m_add_iommu_flags(&entry_content, 0, iommu_pte_flags);
>
> + p2m_set_access(p2m, gfn, p2ma);
> p2m->write_p2m_entry(p2m, gfn, p2m_entry, entry_content, 2);
> /* NB: paging_write_p2m_entry() handles tlb flushes properly */
> }
> @@ -749,8 +828,7 @@ p2m_pt_get_entry(struct p2m_domain *p2m, gfn_t gfn_,
> * XXX Once we start explicitly registering MMIO regions in the p2m
> * XXX we will return p2m_invalid for unmapped gfns */
> *t = p2m_mmio_dm;
> - /* Not implemented except with EPT */
> - *a = p2m_access_rwx;
> + *a = p2m_access_n;
>
> if ( gfn > p2m->max_mapped_pfn )
> {
> @@ -813,6 +891,7 @@ pod_retry_l3:
> l1_table_offset(addr));
> *t = p2m_recalc_type(recalc || _needs_recalc(flags),
> p2m_flags_to_type(flags), p2m, gfn);
> + *a = p2m_get_access(p2m, gfn);
> unmap_domain_page(l3e);
>
> ASSERT(mfn_valid(mfn) || !p2m_is_ram(*t));
> @@ -852,6 +931,7 @@ pod_retry_l2:
> mfn = _mfn(l2e_get_pfn(*l2e) + l1_table_offset(addr));
> *t = p2m_recalc_type(recalc || _needs_recalc(flags),
> p2m_flags_to_type(flags), p2m, gfn);
> + *a = p2m_get_access(p2m, gfn);
> unmap_domain_page(l2e);
>
> ASSERT(mfn_valid(mfn) || !p2m_is_ram(*t));
> @@ -888,6 +968,7 @@ pod_retry_l1:
> }
> mfn = l1e_get_mfn(*l1e);
> *t = p2m_recalc_type(recalc || _needs_recalc(flags), l1t, p2m, gfn);
> + *a = p2m_get_access(p2m, gfn);
> unmap_domain_page(l1e);
>
> ASSERT(mfn_valid(mfn) || !p2m_is_ram(*t) || p2m_is_paging(*t));
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index c53cab4..12e2d24 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -675,6 +675,12 @@ void p2m_teardown(struct p2m_domain *p2m)
>
> d = p2m->domain;
>
> + if ( p2m->mem_access_settings )
> + {
> + radix_tree_destroy(p2m->mem_access_settings, NULL);
> + xfree(p2m->mem_access_settings);
> + }
> +
> p2m_lock(p2m);
> ASSERT(atomic_read(&d->shr_pages) == 0);
> p2m->phys_table = pagetable_null();
> diff --git a/xen/arch/x86/monitor.c b/xen/arch/x86/monitor.c
> index 3fb6531..18b88a1 100644
> --- a/xen/arch/x86/monitor.c
> +++ b/xen/arch/x86/monitor.c
> @@ -20,10 +20,13 @@
> */
>
> #include <asm/monitor.h>
> +#include <asm/p2m.h>
> #include <public/vm_event.h>
>
> int arch_monitor_init_domain(struct domain *d)
> {
> + struct p2m_domain *p2m = p2m_get_hostp2m(d);
> +
> if ( !d->arch.monitor.msr_bitmap )
> d->arch.monitor.msr_bitmap = xzalloc_array(struct monitor_msr_bitmap,
> 2);
> @@ -31,6 +34,16 @@ int arch_monitor_init_domain(struct domain *d)
> if ( !d->arch.monitor.msr_bitmap )
> return -ENOMEM;
>
> + if ( cpu_has_svm && !p2m->mem_access_settings )
> + {
> + p2m->mem_access_settings = xmalloc(struct radix_tree_root);
> +
> + if( !p2m->mem_access_settings )
> + return -ENOMEM;
This will leak d->arch.monitor.msr_bitmap. You need to use the `goto
out_free:` pattern.
Everything else looks OK.
-George
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