xsplice: Add support for exception tables.

Add support for exception tables contained within xSplice payloads. If an
exception occurs search either the main exception table or a particular
active payload's exception table depending on the instruction pointer.

Also we add an test-case to make sure we have an exception that
is handled.

To not grow the code-base if xSplice is not compiled in we add
certain #define to help in determining if code needs to be __init
or not.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/xen/arch/x86/extable.c b/xen/arch/x86/extable.c
index 2a06ccaaf533640bf255fd46dc2be546ab26f6ed..349df7944cbdcba89891b4f3156cb634693f00db 100644 (file)
--- a/xen/arch/x86/extable.c
+++ b/xen/arch/x86/extable.c
@@ -7,6 +7,7 @@
 #include <xen/spinlock.h>
 #include <asm/uaccess.h>
 #include <xen/virtual_region.h>
+#include <xen/xsplice.h>
 
 #define EX_FIELD(ptr, field) ((unsigned long)&(ptr)->field + (ptr)->field)
 
@@ -20,7 +21,7 @@ static inline unsigned long ex_cont(const struct exception_table_entry *x)
        return EX_FIELD(x, cont);
 }
 
-static int __init cmp_ex(const void *a, const void *b)
+static int init_or_xsplice cmp_ex(const void *a, const void *b)
 {
        const struct exception_table_entry *l = a, *r = b;
        unsigned long lip = ex_addr(l);
@@ -35,7 +36,7 @@ static int __init cmp_ex(const void *a, const void *b)
 }
 
 #ifndef swap_ex
-static void __init swap_ex(void *a, void *b, int size)
+static void init_or_xsplice swap_ex(void *a, void *b, int size)
 {
        struct exception_table_entry *l = a, *r = b, tmp;
        long delta = b - a;
@@ -48,19 +49,23 @@ static void __init swap_ex(void *a, void *b, int size)
 }
 #endif
 
-void __init sort_exception_tables(void)
+void init_or_xsplice sort_exception_table(struct exception_table_entry *start,
+                                 const struct exception_table_entry *stop)
 {
-    sort(__start___ex_table, __stop___ex_table - __start___ex_table,
-         sizeof(struct exception_table_entry), cmp_ex, swap_ex);
-    sort(__start___pre_ex_table,
-         __stop___pre_ex_table - __start___pre_ex_table,
+    sort(start, stop - start,
          sizeof(struct exception_table_entry), cmp_ex, swap_ex);
 }
 
-static inline unsigned long
-search_one_table(const struct exception_table_entry *first,
-                 const struct exception_table_entry *last,
-                 unsigned long value)
+void __init sort_exception_tables(void)
+{
+    sort_exception_table(__start___ex_table, __stop___ex_table);
+    sort_exception_table(__start___pre_ex_table, __stop___pre_ex_table);
+}
+
+unsigned long
+search_one_extable(const struct exception_table_entry *first,
+                   const struct exception_table_entry *last,
+                   unsigned long value)
 {
     const struct exception_table_entry *mid;
     long diff;
@@ -85,7 +90,7 @@ search_exception_table(unsigned long addr)
     const struct virtual_region *region = find_text_region(addr);
 
     if ( region && region->ex )
-        return search_one_table(region->ex, region->ex_end - 1, addr);
+        return search_one_extable(region->ex, region->ex_end - 1, addr);
 
     return 0;
 }
@@ -94,7 +99,7 @@ unsigned long
 search_pre_exception_table(struct cpu_user_regs *regs)
 {
     unsigned long addr = (unsigned long)regs->eip;
-    unsigned long fixup = search_one_table(
+    unsigned long fixup = search_one_extable(
         __start___pre_ex_table, __stop___pre_ex_table-1, addr);
     if ( fixup )
     {

diff --git a/xen/arch/x86/test/xen_hello_world_func.c b/xen/arch/x86/test/xen_hello_world_func.c
index 1ad002a19348e02135569378875bb6c64873f58a..2e4af9c556a64241a3824e6965a3252b153954b0 100644 (file)
--- a/xen/arch/x86/test/xen_hello_world_func.c
+++ b/xen/arch/x86/test/xen_hello_world_func.c
@@ -5,9 +5,22 @@
 
 #include <xen/types.h>
 
+#include <asm/uaccess.h>
+
+static unsigned long *non_canonical_addr = (unsigned long *)0xdead000000000000ULL;
+
 /* Our replacement function for xen_extra_version. */
 const char *xen_hello_world(void)
 {
+    unsigned long tmp;
+    int rc;
+    /*
+     * Any BUG, or WARN_ON will contain symbol and payload name. Furthermore
+     * exceptions will be caught and processed properly.
+     */
+    rc = __get_user(tmp, non_canonical_addr);
+    BUG_ON(rc != -EFAULT);
+
     return "Hello World";
 }
 

diff --git a/xen/common/xsplice.c b/xen/common/xsplice.c
index 92117463375a5d2410f66d9b466f0a59af7a49a7..f5505657608019cbccbf7b47ca2e37b0779fbb4a 100644 (file)
--- a/xen/common/xsplice.c
+++ b/xen/common/xsplice.c
@@ -531,6 +531,31 @@ static int prepare_payload(struct payload *payload,
                                   sizeof(*region->frame[i].bugs);
     }
 
+#ifndef CONFIG_ARM
+    sec = xsplice_elf_sec_by_name(elf, ".ex_table");
+    if ( sec )
+    {
+        struct exception_table_entry *s, *e;
+
+        if ( !sec->sec->sh_size ||
+             (sec->sec->sh_size % sizeof(*region->ex)) )
+        {
+            dprintk(XENLOG_ERR, XSPLICE "%s: Wrong size of .ex_table (exp:%lu vs %lu)!\n",
+                    elf->name, sizeof(*region->ex),
+                    sec->sec->sh_size);
+            return -EINVAL;
+        }
+
+        s = sec->load_addr;
+        e = sec->load_addr + sec->sec->sh_size;
+
+        sort_exception_table(s ,e);
+
+        region->ex = s;
+        region->ex_end = e;
+    }
+#endif
+
     return 0;
 }
 

diff --git a/xen/include/asm-x86/uaccess.h b/xen/include/asm-x86/uaccess.h
index 947470d9dfaf81d7c675eb29df24feb01737dc3b..5df26c2ffa1984ac1d7d2cb37ad563acf991d4f8 100644 (file)
--- a/xen/include/asm-x86/uaccess.h
+++ b/xen/include/asm-x86/uaccess.h
@@ -277,5 +277,7 @@ extern struct exception_table_entry __stop___pre_ex_table[];
 
 extern unsigned long search_exception_table(unsigned long);
 extern void sort_exception_tables(void);
+extern void sort_exception_table(struct exception_table_entry *start,
+                                 const struct exception_table_entry *stop);
 
 #endif /* __X86_UACCESS_H__ */

diff --git a/xen/include/xen/xsplice.h b/xen/include/xen/xsplice.h
index 84d782b62b4e34621875344b65a525cfd4e97937..849f58c839ac1c2f53a5134f56b33cda05d7cc0d 100644 (file)
--- a/xen/include/xen/xsplice.h
+++ b/xen/include/xen/xsplice.h
@@ -14,6 +14,16 @@ struct xen_sysctl_xsplice_op;
 #include <xen/elfstructs.h>
 #ifdef CONFIG_XSPLICE
 
+/*
+ * We use alternative and exception table code - which by default are __init
+ * only, however we need them during runtime. These macros allows us to build
+ * the image with these functions built-in. (See the #else below).
+ */
+#define init_or_xsplice_const
+#define init_or_xsplice_constrel
+#define init_or_xsplice_data
+#define init_or_xsplice
+
 /* Convenience define for printk. */
 #define XSPLICE             "xsplice: "
 /* ELF payload special section names. */
@@ -70,6 +80,15 @@ void arch_xsplice_mask(void);
 void arch_xsplice_unmask(void);
 #else
 
+/*
+ * If not compiling with xSplice certain functionality should stay as
+ * __init.
+ */
+#define init_or_xsplice_const       __initconst
+#define init_or_xsplice_constrel    __initconstrel
+#define init_or_xsplice_data        __initdata
+#define init_or_xsplice             __init
+
 #include <xen/errno.h> /* For -ENOSYS */
 static inline int xsplice_op(struct xen_sysctl_xsplice_op *op)
 {