Re: [PATCH v4 07/34] arm/x86: Use struct virtual_region to do bug, symbol, and (x86) exception tables

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

. snip..
> > +struct virtual_region kernel_text = {
> 
> static
> 
> > +    .list = LIST_HEAD_INIT(kernel_text.list),
> > +    .start = (unsigned long)_stext,
> > +    .end = (unsigned long)_etext,
> > +#ifdef CONFIG_X86
> > +    .ex = (struct exception_table_entry *)__start___ex_table,
> > +    .ex_end = (struct exception_table_entry *)__stop___ex_table,
> > +#endif
> 
> Is this together with ...
> 
> > +/*
> > + * Becomes irrelevant when __init sections are cleared.
> > + */
> > +struct virtual_region kernel_inittext  = {
> > +    .list = LIST_HEAD_INIT(kernel_inittext.list),
> > +    .skip = ignore_if_active,
> > +    .start = (unsigned long)_sinittext,
> > +    .end = (unsigned long)_einittext,
> > +#ifdef CONFIG_X86
> > +    /* Even if they are __init their exception entry still gets stuck here. */
> > +    .ex = (struct exception_table_entry *)__start___ex_table,
> > +    .ex_end = (struct exception_table_entry *)__stop___ex_table,
> > +#endif
> 
> ... this really a good idea? I.e. are there not going to be any
> odd side effects because of that redundancy?

None. If the EIP falls within _stext and _etext then its 'ex' table
will be scanned. If _inittext and _einittext then this one. Both of
them end up scanning the same exact exception table (which is kind
silly) - but there are no side-effect.

It would be good to only have __init related exceptions on the __inittext
(and also ditch the __init exception tables once the boot is completed)
but I am not exactly sure how to automatically make the macros resolve
what sections it should go in. That is a further TODO though.
> 
> Also note that the comment preceding this object is a single line one.
> 
> > +/*
> > + * No locking. Additions are done either at startup (when there is only
> > + * one CPU) or when all CPUs are running without IRQs.
> > + *
> > + * Deletions are big tricky. We MUST make sure all but one CPU
> > + * are running cpu_relax().
> > + *
> > + */
> > +LIST_HEAD(virtual_region_list);
> 
> I wonder whether this wouldn't better be static, with the iterator
> that the various parties need getting put here as an out-of-line
> function (instead of getting open coded in a couple of places).

There are three users of this list:
 * search_exception_table - which ends up calling search_one_table
    if within start->end and if region->ex is defined.
 * do_invalid_trap (x86 and ARM) - where both scan start->end.
 * symbols_lookup - where we scan start->end.

The last two could be unified in a:

struct virtual_region search_virtual_region(unsigned long addr);

And the first one can use this and then check if region->ex is set as well.

[trying it out]

.. snip..
> > @@ -108,13 +127,17 @@ const char *symbols_lookup(unsigned long addr,
> >  {
> >      unsigned long i, low, high, mid;
> >      unsigned long symbol_end = 0;
> > +    symbols_lookup_t symbol_lookup = NULL;
> 
> Pointless initializer.

I believe we need it. That is the contents on the stack can be garbage
and the __is_active_kernel_text won't update symbol_lookup unless
it finds a match. Ah, and also the compiler is unhappy:

symbols.c: In function ‘symbols_lookup’:
symbols.c:136:8: error: ‘symbol_lookup’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
     if (symbol_lookup)
        ^
cc1: all warnings being treated as errors

> 
> >      namebuf[KSYM_NAME_LEN] = 0;
> >      namebuf[0] = 0;
> >  
> > -    if (!is_active_kernel_text(addr))
> > +    if (!__is_active_kernel_text(addr, &symbol_lookup))
> >          return NULL;
> >  
> > +    if (symbol_lookup)
> > +        return (symbol_lookup)(addr, symbolsize, offset, namebuf);
> 
> Note that there are few coding style issues here (missing blanks,
> superfluous parentheses).

That file uses a different StyleGuide. The Linux one. Which reminds me
that __is_active_kernel_text needs to adhere to different StyleGuide.

> 
> > --- /dev/null
> > +++ b/xen/include/xen/bug_ex_symbols.h
> > @@ -0,0 +1,74 @@
> > +/*
> > + * Copyright (c) 2016 Oracle and/or its affiliates. All rights reserved.
> > + *
> > + */
> > +
> > +#ifndef __BUG_EX_SYMBOL_LIST__
> > +#define __BUG_EX_SYMBOL_LIST__
> > +
> > +#include <xen/config.h>
> > +#include <xen/list.h>
> > +#include <xen/symbols.h>
> > +
> > +#ifdef CONFIG_X86
> > +#include <asm/uaccess.h>
> > +#endif
> 
> Why?

Otherwise the compilation will fail on ARM as they do not have exceptions
(and no asm/uaccess.h file)
> 
> > +#include <asm/bug.h>
> > +
> > +struct virtual_region
> > +{
> > +    struct list_head list;
> > +
> > +#define CHECKING_SYMBOL         (1<<1)
> > +#define CHECKING_BUG_FRAME      (1<<2)
> > +#define CHECKING_EXCEPTION      (1<<3)
> > +    /*
> > +     * Whether to skip this region for particular searches. The flag
> > +     * can be CHECKING_[SYMBOL|BUG_FRAMES|EXCEPTION].
> > +     *
> > +     * If the function returns 1 this region will be skipped.
> > +     */
> > +    bool_t (*skip)(unsigned int flag, unsigned long priv);
> > +
> > +    unsigned long start;        /* Virtual address start. */
> > +    unsigned long end;          /* Virtual address start. */
> > +
> > +    /*
> > +     * If ->skip returns false for CHECKING_SYMBOL we will use
> > +     * 'symbols_lookup' callback to retrieve the name of the
> > +     * addr between start and end. If this is NULL the
> > +     * default lookup mechanism is used (the skip value is
> > +     * ignored).
> > +     */
> > +    symbols_lookup_t symbols_lookup;
> > +
> > +    struct {
> > +        struct bug_frame *bugs; /* The pointer to array of bug frames. */
> > +        ssize_t n_bugs;         /* The number of them. */
> > +    } frame[BUGFRAME_NR];
> > +
> > +#ifdef CONFIG_X86
> > +    struct exception_table_entry *ex;
> > +    struct exception_table_entry *ex_end;
> > +#endif
> 
> The bug frame and exception related data are kind of odd to be
> placed in a structure with this name. Would that not better be
> accessed through ...
> 
> > +    unsigned long priv;         /* To be used by above funcionts if need to. */
> 
> ... this by the interested parties?

This had been re-worked with Andrew's suggestions and yours. Pls see:


From d542ae2b6de421c5402888519d4d11a09abe8d46 Mon Sep 17 00:00:00 2001
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Thu, 10 Mar 2016 16:35:50 -0500
Subject: [PATCH] arm/x86: Use struct virtual_region to do bug, symbol, and
 (x86) exception tables lookup.

During execution of the hypervisor we have two regions of
executable code - stext -> _etext, and _sinittext -> _einitext.

The later is not needed after bootup.

We also have various built-in macros and functions to search
in between those two swaths depending on the state of the system.

That is either for bug_frames, exceptions (x86) or symbol
names for the instruction.

With xSplice in the picture - we need a mechansim for new payloads
to searched as well for all of this.

Originally we had extra 'if (xsplice)...' but that gets
a bit tiring and does not hook up nicely.

This 'struct virtual_region' and virtual_region_list provide a
mechanism to search for the bug_frames, exception table,
and symbol names entries without having various calls in
other sub-components in the system.

Code which wishes to participate in bug_frames and exception table
entries search has to only use two public APIs:
 - register_virtual_region
 - unregister_virtual_region

to let the core code know.

If the ->lookup_symbol is not then the default internal symbol lookup
mechanism is used.

Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

---
Cc: Stefano Stabellini <stefano.stabellini@citrix.com>
Cc: Julien Grall <julien.grall@arm.com>
Cc: Keir Fraser <keir@xen.org>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>

v4: New patch.
v5:
 - Rename to virtual_region.
 - Ditch the 'skip' function.
 - Remove the _stext.
 - Use RCU lists.
 - Add a search function.
---
---
 xen/arch/arm/setup.c             |   4 ++
 xen/arch/arm/traps.c             |  39 ++++++----
 xen/arch/x86/extable.c           |  12 +++-
 xen/arch/x86/setup.c             |   6 ++
 xen/arch/x86/traps.c             |  40 ++++++-----
 xen/common/Makefile              |   1 +
 xen/common/symbols.c             |  11 ++-
 xen/common/virtual_region.c      | 151 +++++++++++++++++++++++++++++++++++++++
 xen/include/xen/symbols.h        |   9 +++
 xen/include/xen/virtual_region.h |  56 +++++++++++++++
 10 files changed, 292 insertions(+), 37 deletions(-)
 create mode 100644 xen/common/virtual_region.c
 create mode 100644 xen/include/xen/virtual_region.h

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 6d205a9..09ff1ea 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -34,6 +34,7 @@
 #include <xen/keyhandler.h>
 #include <xen/cpu.h>
 #include <xen/pfn.h>
+#include <xen/virtual_region.h>
 #include <xen/vmap.h>
 #include <xen/libfdt/libfdt.h>
 #include <xen/acpi.h>
@@ -860,6 +861,9 @@ void __init start_xen(unsigned long boot_phys_offset,
 
     system_state = SYS_STATE_active;
 
+    /* Must be done past setting system_state. */
+    unregister_init_virtual_region();
+
     domain_unpause_by_systemcontroller(dom0);
 
     /* Switch on to the dynamically allocated stack for the idle vcpu
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 31d2115..97e40bb 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -31,6 +31,7 @@
 #include <xen/softirq.h>
 #include <xen/domain_page.h>
 #include <xen/perfc.h>
+#include <xen/virtual_region.h>
 #include <public/sched.h>
 #include <public/xen.h>
 #include <asm/debugger.h>
@@ -101,6 +102,8 @@ integer_param("debug_stack_lines", debug_stack_lines);
 
 void init_traps(void)
 {
+    setup_virtual_regions();
+
     /* Setup Hyp vector base */
     WRITE_SYSREG((vaddr_t)hyp_traps_vector, VBAR_EL2);
 
@@ -1077,27 +1080,33 @@ void do_unexpected_trap(const char *msg, struct cpu_user_regs *regs)
 
 int do_bug_frame(struct cpu_user_regs *regs, vaddr_t pc)
 {
-    const struct bug_frame *bug;
+    const struct bug_frame *bug = NULL;
     const char *prefix = "", *filename, *predicate;
     unsigned long fixup;
-    int id, lineno;
-    static const struct bug_frame *const stop_frames[] = {
-        __stop_bug_frames_0,
-        __stop_bug_frames_1,
-        __stop_bug_frames_2,
-        NULL
-    };
+    int id = -1, lineno;
+    struct virtual_region *region;
 
-    for ( bug = __start_bug_frames, id = 0; stop_frames[id]; ++bug )
+    region = search_virtual_regions(pc);
+    if ( region )
     {
-        while ( unlikely(bug == stop_frames[id]) )
-            ++id;
+        for ( id = 0; id < BUGFRAME_NR; id++ )
+        {
+            const struct bug_frame *b;
+            unsigned int i;
 
-        if ( ((vaddr_t)bug_loc(bug)) == pc )
-            break;
+            for ( i = 0, b = region->frame[id].bugs;
+                  i < region->frame[id].n_bugs; b++, i++ )
+            {
+                if ( ((vaddr_t)bug_loc(b)) == pc )
+                {
+                    bug = b;
+                    goto found;
+                }
+            }
+        }
     }
-
-    if ( !stop_frames[id] )
+ found:
+    if ( !bug )
         return -ENOENT;
 
     /* WARN, BUG or ASSERT: decode the filename pointer and line number. */
diff --git a/xen/arch/x86/extable.c b/xen/arch/x86/extable.c
index 89b5bcb..d0f1361 100644
--- a/xen/arch/x86/extable.c
+++ b/xen/arch/x86/extable.c
@@ -1,10 +1,12 @@
 
-#include <xen/config.h>
 #include <xen/init.h>
+#include <xen/list.h>
 #include <xen/perfc.h>
+#include <xen/rcupdate.h>
 #include <xen/sort.h>
 #include <xen/spinlock.h>
 #include <asm/uaccess.h>
+#include <xen/virtual_region.h>
 
 #define EX_FIELD(ptr, field) ((unsigned long)&(ptr)->field + (ptr)->field)
 
@@ -80,8 +82,12 @@ search_one_table(const struct exception_table_entry *first,
 unsigned long
 search_exception_table(unsigned long addr)
 {
-    return search_one_table(
-        __start___ex_table, __stop___ex_table-1, addr);
+    struct virtual_region *region = search_virtual_regions(addr);
+
+    if ( region && region->ex )
+        return search_one_table(region->ex, region->ex_end-1, addr);
+
+    return 0;
 }
 
 unsigned long
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 1876a28..20cd9b3 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -26,6 +26,7 @@
 #include <xen/pfn.h>
 #include <xen/nodemask.h>
 #include <xen/tmem_xen.h>
+#include <xen/virtual_region.h>
 #include <xen/watchdog.h>
 #include <public/version.h>
 #include <compat/platform.h>
@@ -514,6 +515,9 @@ static void noinline init_done(void)
 
     system_state = SYS_STATE_active;
 
+    /* MUST be done prior to removing .init data. */
+    unregister_init_virtual_region();
+
     domain_unpause_by_systemcontroller(hardware_domain);
 
     /* Zero the .init code and data. */
@@ -616,6 +620,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     smp_prepare_boot_cpu();
     sort_exception_tables();
 
+    setup_virtual_regions();
+
     /* Full exception support from here on in. */
 
     loader = (mbi->flags & MBI_LOADERNAME)
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 6fbb1cf..f90d6ac 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -48,6 +48,7 @@
 #include <xen/kexec.h>
 #include <xen/trace.h>
 #include <xen/paging.h>
+#include <xen/virtual_region.h>
 #include <xen/watchdog.h>
 #include <asm/system.h>
 #include <asm/io.h>
@@ -1132,18 +1133,12 @@ static int emulate_forced_invalid_op(struct cpu_user_regs *regs)
 
 void do_invalid_op(struct cpu_user_regs *regs)
 {
-    const struct bug_frame *bug;
+    const struct bug_frame *bug = NULL;
     u8 bug_insn[2];
     const char *prefix = "", *filename, *predicate, *eip = (char *)regs->eip;
     unsigned long fixup;
-    int id, lineno;
-    static const struct bug_frame *const stop_frames[] = {
-        __stop_bug_frames_0,
-        __stop_bug_frames_1,
-        __stop_bug_frames_2,
-        __stop_bug_frames_3,
-        NULL
-    };
+    int id = -1, lineno;
+    struct virtual_region *region;
 
     DEBUGGER_trap_entry(TRAP_invalid_op, regs);
 
@@ -1160,16 +1155,29 @@ void do_invalid_op(struct cpu_user_regs *regs)
          memcmp(bug_insn, "\xf\xb", sizeof(bug_insn)) )
         goto die;
 
-    for ( bug = __start_bug_frames, id = 0; stop_frames[id]; ++bug )
+    region = search_virtual_regions(regs->eip);
+    if ( region )
     {
-        while ( unlikely(bug == stop_frames[id]) )
-            ++id;
-        if ( bug_loc(bug) == eip )
-            break;
+        for ( id = 0; id < BUGFRAME_NR; id++ )
+        {
+            const struct bug_frame *b;
+            unsigned int i;
+
+            for ( i = 0, b = region->frame[id].bugs;
+                  i < region->frame[id].n_bugs; b++, i++ )
+            {
+                if ( bug_loc(b) == eip )
+                {
+                    bug = b;
+                    goto found;
+                }
+            }
+        }
     }
-    if ( !stop_frames[id] )
-        goto die;
 
+ found:
+    if ( !bug )
+        goto die;
     eip += sizeof(bug_insn);
     if ( id == BUGFRAME_run_fn )
     {
diff --git a/xen/common/Makefile b/xen/common/Makefile
index 77de27e..e43ec49 100644
--- a/xen/common/Makefile
+++ b/xen/common/Makefile
@@ -51,6 +51,7 @@ obj-y += time.o
 obj-y += timer.o
 obj-y += trace.o
 obj-y += version.o
+obj-y += virtual_region.o
 obj-y += vm_event.o
 obj-y += vmap.o
 obj-y += vsprintf.o
diff --git a/xen/common/symbols.c b/xen/common/symbols.c
index a59c59d..bba0f2e 100644
--- a/xen/common/symbols.c
+++ b/xen/common/symbols.c
@@ -17,6 +17,7 @@
 #include <xen/lib.h>
 #include <xen/string.h>
 #include <xen/spinlock.h>
+#include <xen/virtual_region.h>
 #include <public/platform.h>
 #include <xen/guest_access.h>
 
@@ -97,8 +98,7 @@ static unsigned int get_symbol_offset(unsigned long pos)
 
 bool_t is_active_kernel_text(unsigned long addr)
 {
-    return (is_kernel_text(addr) ||
-            (system_state < SYS_STATE_active && is_kernel_inittext(addr)));
+    return !!search_virtual_regions(addr);
 }
 
 const char *symbols_lookup(unsigned long addr,
@@ -108,13 +108,18 @@ const char *symbols_lookup(unsigned long addr,
 {
     unsigned long i, low, high, mid;
     unsigned long symbol_end = 0;
+    struct virtual_region *region;
 
     namebuf[KSYM_NAME_LEN] = 0;
     namebuf[0] = 0;
 
-    if (!is_active_kernel_text(addr))
+    region = search_virtual_regions(addr);
+    if (!region)
         return NULL;
 
+    if (region->symbols_lookup)
+        return region->symbols_lookup(addr, symbolsize, offset, namebuf);
+
         /* do a binary search on the sorted symbols_addresses array */
     low = 0;
     high = symbols_num_syms;
diff --git a/xen/common/virtual_region.c b/xen/common/virtual_region.c
new file mode 100644
index 0000000..618a312
--- /dev/null
+++ b/xen/common/virtual_region.c
@@ -0,0 +1,151 @@
+/*
+ * Copyright (c) 2016 Oracle and/or its affiliates. All rights reserved.
+ *
+ */
+
+#include <xen/config.h>
+#include <xen/init.h>
+#include <xen/kernel.h>
+#include <xen/rcupdate.h>
+#include <xen/spinlock.h>
+#include <xen/virtual_region.h>
+
+static struct virtual_region compiled = {
+    .list = LIST_HEAD_INIT(compiled.list),
+    .start = (unsigned long)_stext,
+    .end = (unsigned long)_etext,
+#ifdef CONFIG_X86
+    .ex = (struct exception_table_entry *)__start___ex_table,
+    .ex_end = (struct exception_table_entry *)__stop___ex_table,
+#endif
+};
+
+/* Becomes irrelevant when __init sections are cleared. */
+static struct virtual_region compiled_init __initdata = {
+    .list = LIST_HEAD_INIT(compiled_init.list),
+    .start = (unsigned long)_sinittext,
+    .end = (unsigned long)_einittext,
+#ifdef CONFIG_X86
+    /* Even if they are __init their exception entry still gets stuck here. */
+    .ex = (struct exception_table_entry *)__start___ex_table,
+    .ex_end = (struct exception_table_entry *)__stop___ex_table,
+#endif
+};
+
+/*
+ * RCU locking. Additions are done either at startup (when there is only
+ * one CPU) or when all CPUs are running without IRQs.
+ *
+ * Deletions are big tricky. We do it when xSplicing (all CPUs running
+ * without IRQs) or during bootup (when clearing the init).
+ *
+ * Hence we use list_del_rcu (which sports an memory fence) and a spinlock
+ * on deletion.
+ *
+ * All readers of virtual_region_list MUST use list list_for_each_entry_rcu.
+ *
+ */
+static LIST_HEAD(virtual_region_list);
+static DEFINE_SPINLOCK(virtual_region_lock);
+
+struct virtual_region* search_virtual_regions(unsigned long addr)
+{
+    struct virtual_region *region;
+
+    list_for_each_entry_rcu( region, &virtual_region_list, list )
+    {
+        if ( addr >= region->start && addr < region->end )
+            return region;
+    }
+
+    return NULL;
+}
+
+int register_virtual_region(struct virtual_region *r)
+{
+    ASSERT(!local_irq_is_enabled());
+
+    list_add_tail_rcu(&r->list, &virtual_region_list);
+
+    return 0;
+}
+
+static void __unregister_virtual_region(struct virtual_region *r)
+{
+    unsigned long flags;
+
+    spin_lock_irqsave(&virtual_region_lock, flags);
+    list_del_rcu(&r->list);
+    spin_unlock_irqrestore(&virtual_region_lock, flags);
+    /*
+     * We do not need to invoke call_rcu.
+     *
+     * This is due to the fact that on the deletion we have made sure
+     * to use spinlocks (to guard against somebody else calling
+     * unregister_virtual_region) and list_deletion spiced with an memory
+     * barrier - which will flush out the cache lines in other CPUs.
+     *
+     * That protects us from corrupting the list as the readers all
+     * use list_for_each_entry_rcu which is safe against concurrent
+     * deletions.
+     */
+}
+
+void unregister_virtual_region(struct virtual_region *r)
+{
+    /* Expected to be called from xSplice - which has IRQs disabled. */
+    ASSERT(!local_irq_is_enabled());
+
+    __unregister_virtual_region(r);
+}
+
+void unregister_init_virtual_region(void)
+{
+    BUG_ON(system_state != SYS_STATE_active);
+
+    __unregister_virtual_region(&compiled_init);
+}
+
+void __init setup_virtual_regions(void)
+{
+    ssize_t sz;
+    unsigned int i;
+    static const struct bug_frame *const stop_frames[] = {
+        __start_bug_frames,
+        __stop_bug_frames_0,
+        __stop_bug_frames_1,
+        __stop_bug_frames_2,
+#ifdef CONFIG_X86
+        __stop_bug_frames_3,
+#endif
+        NULL
+    };
+
+    /* N.B. idx != i */
+    for ( i = 1; stop_frames[i]; i++ )
+    {
+        const struct bug_frame *s;
+
+        s = stop_frames[i-1];
+        sz = stop_frames[i] - s;
+
+        compiled.frame[i-1].n_bugs = sz;
+        compiled.frame[i-1].bugs = s;
+
+        compiled_init.frame[i-1].n_bugs = sz;
+        compiled_init.frame[i-1].bugs = s;
+    }
+
+    register_virtual_region(&compiled_init);
+    register_virtual_region(&compiled);
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/include/xen/symbols.h b/xen/include/xen/symbols.h
index 1fa0537..fa353f8 100644
--- a/xen/include/xen/symbols.h
+++ b/xen/include/xen/symbols.h
@@ -5,6 +5,15 @@
 
 #define KSYM_NAME_LEN 127
 
+/*
+ * Typedef for the callback functions that symbols_lookup
+ * can call if virtual_region_list has an callback for it.
+ */
+typedef const char *(symbols_lookup_t)(unsigned long addr,
+                                       unsigned long *symbolsize,
+                                       unsigned long *offset,
+                                       char *namebuf);
+
 /* Lookup an address. */
 const char *symbols_lookup(unsigned long addr,
                            unsigned long *symbolsize,
diff --git a/xen/include/xen/virtual_region.h b/xen/include/xen/virtual_region.h
new file mode 100644
index 0000000..bf15fe9
--- /dev/null
+++ b/xen/include/xen/virtual_region.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2016 Oracle and/or its affiliates. All rights reserved.
+ *
+ */
+
+#ifndef __BUG_EX_SYMBOL_LIST__
+#define __BUG_EX_SYMBOL_LIST__
+
+#include <xen/config.h>
+#include <xen/list.h>
+#include <xen/symbols.h>
+
+#ifdef CONFIG_X86
+#include <asm/uaccess.h>
+#endif
+#include <asm/bug.h>
+
+struct virtual_region
+{
+    struct list_head list;
+    unsigned long start;        /* Virtual address start. */
+    unsigned long end;          /* Virtual address start. */
+
+    /*
+     * If this is NULL the default lookup mechanism is used.
+     */
+    symbols_lookup_t *symbols_lookup;
+
+    struct {
+        const struct bug_frame *bugs; /* The pointer to array of bug frames. */
+        ssize_t n_bugs;         /* The number of them. */
+    } frame[BUGFRAME_NR];
+
+#ifdef CONFIG_X86
+    struct exception_table_entry *ex;
+    struct exception_table_entry *ex_end;
+#endif
+};
+
+extern struct virtual_region *search_virtual_regions(unsigned long addr);
+extern void setup_virtual_regions(void);
+extern void unregister_init_virtual_region(void);
+extern int register_virtual_region(struct virtual_region *r);
+extern void unregister_virtual_region(struct virtual_region *r);
+
+#endif /* __BUG_EX_SYMBOL_LIST__ */
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.5.0



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