[RFC v2 16/26] mm/asi: Option to map current task into ASI

[Alexandre Chartre]

Add an option to map the current task into an ASI page-table.
The task is mapped when entering isolation and unmapped on
abort/exit.

Signed-off-by: Alexandre Chartre <alexandre.char...@oracle.com>
---
 arch/x86/include/asm/asi.h  |    2 ++
 arch/x86/mm/asi.c           |   25 +++++++++++++++++++++----
 arch/x86/mm/asi_pagetable.c |    4 ++--
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h
index 1ac8fd3..a277e43 100644
--- a/arch/x86/include/asm/asi.h
+++ b/arch/x86/include/asm/asi.h
@@ -17,6 +17,7 @@
  */
 #define ASI_MAP_STACK_CANARY   0x01    /* map stack canary */
 #define ASI_MAP_CPU_PTR                0x02    /* for 
get_cpu_var()/this_cpu_ptr() */
+#define ASI_MAP_CURRENT_TASK   0x04    /* map the current task */
 
 enum page_table_level {
        PGT_LEVEL_PTE,
@@ -31,6 +32,7 @@ enum page_table_level {
 struct asi {
        spinlock_t              lock;           /* protect all attributes */
        pgd_t                   *pgd;           /* ASI page-table */
+       int                     mapping_flags;  /* map flags */
        struct list_head        mapping_list;   /* list of VA range mapping */
 
        /*
diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c
index f049438..acd1135 100644
--- a/arch/x86/mm/asi.c
+++ b/arch/x86/mm/asi.c
@@ -28,6 +28,7 @@ struct asi_map_option {
 struct asi_map_option asi_map_percpu_options[] = {
        { ASI_MAP_STACK_CANARY, &fixed_percpu_data, sizeof(fixed_percpu_data) },
        { ASI_MAP_CPU_PTR, &this_cpu_off, sizeof(this_cpu_off) },
+       { ASI_MAP_CURRENT_TASK, &current_task, sizeof(current_task) },
 };
 
 static void asi_log_fault(struct asi *asi, struct pt_regs *regs,
@@ -96,8 +97,9 @@ bool asi_fault(struct pt_regs *regs, unsigned long error_code,
        return true;
 }
 
-static int asi_init_mapping(struct asi *asi, int flags)
+static int asi_init_mapping(struct asi *asi)
 {
+       int flags = asi->mapping_flags;
        struct asi_map_option *option;
        int i, err;
 
@@ -164,8 +166,9 @@ struct asi *asi_create(int map_flags)
        spin_lock_init(&asi->lock);
        spin_lock_init(&asi->fault_lock);
        asi_init_backend(asi);
+       asi->mapping_flags = map_flags;
 
-       err = asi_init_mapping(asi, map_flags);
+       err = asi_init_mapping(asi);
        if (err)
                goto error;
 
@@ -248,6 +251,15 @@ int asi_enter(struct asi *asi)
                goto err_clear_asi;
 
        /*
+        * Optionally, also map the current task.
+        */
+       if (asi->mapping_flags & ASI_MAP_CURRENT_TASK) {
+               err = asi_map(asi, current, sizeof(struct task_struct));
+               if (err)
+                       goto err_unmap_stack;
+       }
+
+       /*
         * Instructions ordering is important here because we should be
         * able to deal with any interrupt/exception which will abort
         * the isolation and restore CR3 to its original value:
@@ -269,7 +281,7 @@ int asi_enter(struct asi *asi)
        if (!original_cr3) {
                WARN_ON(1);
                err = -EINVAL;
-               goto err_unmap_stack;
+               goto err_unmap_task;
        }
        asi_session->original_cr3 = original_cr3;
 
@@ -286,6 +298,9 @@ int asi_enter(struct asi *asi)
 
        return 0;
 
+err_unmap_task:
+       if (asi->mapping_flags & ASI_MAP_CURRENT_TASK)
+               asi_unmap(asi, current);
 err_unmap_stack:
        asi_unmap(asi, current->stack);
 err_clear_asi:
@@ -345,8 +360,10 @@ void asi_exit(struct asi *asi)
         */
        asi_session->abort_depth = 0;
 
-       /* unmap stack */
+       /* unmap stack and task */
        asi_unmap(asi, current->stack);
+       if (asi->mapping_flags & ASI_MAP_CURRENT_TASK)
+               asi_unmap(asi, current);
 }
 EXPORT_SYMBOL(asi_exit);
 
diff --git a/arch/x86/mm/asi_pagetable.c b/arch/x86/mm/asi_pagetable.c
index bcc95f2..8076626 100644
--- a/arch/x86/mm/asi_pagetable.c
+++ b/arch/x86/mm/asi_pagetable.c
@@ -714,7 +714,7 @@ int asi_map_range(struct asi *asi, void *ptr, size_t size,
         * Don't log info the current stack because it is mapped/unmapped
         * everytime we enter/exit isolation.
         */
-       if (ptr != current->stack) {
+       if (ptr != current->stack && ptr != current) {
                pr_debug("ASI %p: MAP %px/%lx/%d -> %lx-%lx\n",
                         asi, ptr, size, level, map_addr, map_end);
                if (map_addr < addr)
@@ -1001,7 +1001,7 @@ void asi_unmap(struct asi *asi, void *ptr)
         * Don't log info the current stack because it is mapped/unmapped
         * everytime we enter/exit isolation.
         */
-       if (ptr != current->stack) {
+       if (ptr != current->stack && ptr != current) {
                pr_debug("ASI %p: UNMAP %px/%lx/%d\n", asi, ptr,
                         range_mapping->size, range_mapping->level);
        }
-- 
1.7.1