[RFC PATCH v2 16/19] heki: x86: Update permissions counters when guest page permissions change
Mickaël Salaün
mic at digikod.net
Mon Nov 13 02:23:23 UTC 2023
From: Madhavan T. Venkataraman <madvenka at linux.microsoft.com>
When permissions are changed on an existing mapping, update the
permissions counters.
Cc: Borislav Petkov <bp at alien8.de>
Cc: Dave Hansen <dave.hansen at linux.intel.com>
Cc: H. Peter Anvin <hpa at zytor.com>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Kees Cook <keescook at chromium.org>
Cc: Madhavan T. Venkataraman <madvenka at linux.microsoft.com>
Cc: Mickaël Salaün <mic at digikod.net>
Cc: Paolo Bonzini <pbonzini at redhat.com>
Cc: Sean Christopherson <seanjc at google.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Vitaly Kuznetsov <vkuznets at redhat.com>
Cc: Wanpeng Li <wanpengli at tencent.com>
Signed-off-by: Madhavan T. Venkataraman <madvenka at linux.microsoft.com>
---
Changes since v1:
* New patch
---
arch/x86/mm/heki.c | 9 +++++++
arch/x86/mm/pat/set_memory.c | 51 ++++++++++++++++++++++++++++++++++++
include/linux/heki.h | 14 ++++++++++
virt/heki/counters.c | 23 ++++++++++++++++
4 files changed, 97 insertions(+)
diff --git a/arch/x86/mm/heki.c b/arch/x86/mm/heki.c
index c495df0d8772..c0eace9e343f 100644
--- a/arch/x86/mm/heki.c
+++ b/arch/x86/mm/heki.c
@@ -54,3 +54,12 @@ unsigned long heki_flags_to_permissions(unsigned long flags)
return permissions;
}
+
+void heki_pgprot_to_permissions(pgprot_t prot, unsigned long *set,
+ unsigned long *clear)
+{
+ if (pgprot_val(prot) & _PAGE_RW)
+ *set |= MEM_ATTR_WRITE;
+ if (pgprot_val(prot) & _PAGE_NX)
+ *clear |= MEM_ATTR_EXEC;
+}
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index bda9f129835e..6aaa1ce5692c 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -22,6 +22,7 @@
#include <linux/cc_platform.h>
#include <linux/set_memory.h>
#include <linux/memregion.h>
+#include <linux/heki.h>
#include <asm/e820/api.h>
#include <asm/processor.h>
@@ -2056,11 +2057,56 @@ int clear_mce_nospec(unsigned long pfn)
EXPORT_SYMBOL_GPL(clear_mce_nospec);
#endif /* CONFIG_X86_64 */
+#ifdef CONFIG_HEKI
+
+static void heki_change_page_attr_set(unsigned long va, int numpages,
+ pgprot_t set)
+{
+ unsigned long va_end;
+ unsigned long set_permissions = 0, clear_permissions = 0;
+
+ heki_pgprot_to_permissions(set, &set_permissions, &clear_permissions);
+ if (!(set_permissions | clear_permissions))
+ return;
+
+ va_end = va + (numpages << PAGE_SHIFT);
+ heki_update(va, va_end, set_permissions, clear_permissions);
+}
+
+static void heki_change_page_attr_clear(unsigned long va, int numpages,
+ pgprot_t clear)
+{
+ unsigned long va_end;
+ unsigned long set_permissions = 0, clear_permissions = 0;
+
+ heki_pgprot_to_permissions(clear, &clear_permissions, &set_permissions);
+ if (!(set_permissions | clear_permissions))
+ return;
+
+ va_end = va + (numpages << PAGE_SHIFT);
+ heki_update(va, va_end, set_permissions, clear_permissions);
+}
+
+#else /* !CONFIG_HEKI */
+
+static void heki_change_page_attr_set(unsigned long va, int numpages,
+ pgprot_t set)
+{
+}
+
+static void heki_change_page_attr_clear(unsigned long va, int numpages,
+ pgprot_t clear)
+{
+}
+
+#endif /* CONFIG_HEKI */
+
int set_memory_x(unsigned long addr, int numpages)
{
if (!(__supported_pte_mask & _PAGE_NX))
return 0;
+ heki_change_page_attr_clear(addr, numpages, __pgprot(_PAGE_NX));
return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_NX), 0);
}
@@ -2069,11 +2115,14 @@ int set_memory_nx(unsigned long addr, int numpages)
if (!(__supported_pte_mask & _PAGE_NX))
return 0;
+ heki_change_page_attr_set(addr, numpages, __pgprot(_PAGE_NX));
return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_NX), 0);
}
int set_memory_ro(unsigned long addr, int numpages)
{
+ // TODO: What about _PAGE_DIRTY?
+ heki_change_page_attr_clear(addr, numpages, __pgprot(_PAGE_RW));
return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_RW | _PAGE_DIRTY), 0);
}
@@ -2084,11 +2133,13 @@ int set_memory_rox(unsigned long addr, int numpages)
if (__supported_pte_mask & _PAGE_NX)
clr.pgprot |= _PAGE_NX;
+ heki_change_page_attr_clear(addr, numpages, clr);
return change_page_attr_clear(&addr, numpages, clr, 0);
}
int set_memory_rw(unsigned long addr, int numpages)
{
+ heki_change_page_attr_set(addr, numpages, __pgprot(_PAGE_RW));
return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_RW), 0);
}
diff --git a/include/linux/heki.h b/include/linux/heki.h
index d660994d34d0..079b34af07f0 100644
--- a/include/linux/heki.h
+++ b/include/linux/heki.h
@@ -73,6 +73,7 @@ struct heki_hypervisor {
*
* - a page is mapped into the kernel address space
* - a page is unmapped from the kernel address space
+ * - permissions are changed for a mapped page
*/
struct heki {
struct heki_hypervisor *hypervisor;
@@ -81,6 +82,7 @@ struct heki {
enum heki_cmd {
HEKI_MAP,
+ HEKI_UPDATE,
HEKI_UNMAP,
};
@@ -98,6 +100,10 @@ struct heki_args {
/* Command passed by caller. */
enum heki_cmd cmd;
+
+ /* Permissions passed by heki_update(). */
+ unsigned long set;
+ unsigned long clear;
};
/* Callback function called by the table walker. */
@@ -114,11 +120,15 @@ void heki_counters_init(void);
void heki_walk(unsigned long va, unsigned long va_end, heki_func_t func,
struct heki_args *args);
void heki_map(unsigned long va, unsigned long end);
+void heki_update(unsigned long va, unsigned long end, unsigned long set,
+ unsigned long clear);
void heki_unmap(unsigned long va, unsigned long end);
/* Arch-specific functions. */
void heki_arch_early_init(void);
unsigned long heki_flags_to_permissions(unsigned long flags);
+void heki_pgprot_to_permissions(pgprot_t prot, unsigned long *set,
+ unsigned long *clear);
#else /* !CONFIG_HEKI */
@@ -131,6 +141,10 @@ static inline void heki_late_init(void)
static inline void heki_map(unsigned long va, unsigned long end)
{
}
+static inline void heki_update(unsigned long va, unsigned long end,
+ unsigned long set, unsigned long clear)
+{
+}
static inline void heki_unmap(unsigned long va, unsigned long end)
{
}
diff --git a/virt/heki/counters.c b/virt/heki/counters.c
index adc8d566b8a9..d0f830b0775a 100644
--- a/virt/heki/counters.c
+++ b/virt/heki/counters.c
@@ -88,6 +88,13 @@ void heki_callback(struct heki_args *args)
heki_update_counters(counters, 0, permissions, 0);
break;
+ case HEKI_UPDATE:
+ if (!counters)
+ continue;
+ heki_update_counters(counters, permissions, args->set,
+ args->clear);
+ break;
+
case HEKI_UNMAP:
if (WARN_ON_ONCE(!counters))
break;
@@ -131,6 +138,22 @@ void heki_map(unsigned long va, unsigned long end)
heki_func(va, end, &args);
}
+/*
+ * Find the mappings in the given range and update permission counters for
+ * them. Apply permissions in the host page table.
+ */
+void heki_update(unsigned long va, unsigned long end, unsigned long set,
+ unsigned long clear)
+{
+ struct heki_args args = {
+ .cmd = HEKI_UPDATE,
+ .set = set,
+ .clear = clear,
+ };
+
+ heki_func(va, end, &args);
+}
+
/*
* Find the mappings in the given range and revert the permission counters for
* them.
--
2.42.1
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