[Xen-devel] [PATCH v9 17/27] xsplice: Add support for bug frames.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

Add support for handling bug frames contained with xsplice modules. If a
trap occurs search either the kernel bug table or an applied payload's
bug table depending on the instruction pointer.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

v2:- s/module/payload/
   - add build time check in case amount of bug frames expands.
   - add define for the number of bug-frames.
v3:
  - add missing BUGFRAME_NR, squash s/core_size/core/ in earlier patch.
  - Moved code around.
  - Changed per Andrew's recommendation.
  - Fixed style changes.
  - Made it compile under ARM (PRIu32,PRIu64)
v4: Use 'struct virtual_region'
  - Rip more of the is_active_text code.
  - Use one function for the ->skip
  - Include test-case
v5: Rip out the ->skip function.
v7: Add a text check as well.
    Add Andrew's Reviewed-by.
v8: Changed dprintk XENLOG_DEBUG to XENLOG_ERR
v9: Removed pointless check on the side of conditional (sec->sec->sh_size)
  - Added const.
  - Use RCU list.
---
---
 xen/arch/x86/traps.c      |  5 +++--
 xen/common/xsplice.c      | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 xen/include/xen/xsplice.h |  5 +++++
 3 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index f73f7f3..8384158 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -50,6 +50,7 @@
 #include <xen/paging.h>
 #include <xen/virtual_region.h>
 #include <xen/watchdog.h>
+#include <xen/xsplice.h>
 #include <asm/system.h>
 #include <asm/io.h>
 #include <asm/atomic.h>
@@ -1287,7 +1288,7 @@ void do_invalid_op(struct cpu_user_regs *regs)
 
     /* WARN, BUG or ASSERT: decode the filename pointer and line number. */
     filename = bug_ptr(bug);
-    if ( !is_kernel(filename) )
+    if ( !is_kernel(filename) && !is_patch(filename) )
         goto die;
     fixup = strlen(filename);
     if ( fixup > 50 )
@@ -1314,7 +1315,7 @@ void do_invalid_op(struct cpu_user_regs *regs)
     case BUGFRAME_assert:
         /* ASSERT: decode the predicate string pointer. */
         predicate = bug_msg(bug);
-        if ( !is_kernel(predicate) )
+        if ( !is_kernel(predicate) && !is_patch(predicate) )
             predicate = "<unknown>";
 
         printk("Assertion '%s' failed at %s%s:%d\n",
diff --git a/xen/common/xsplice.c b/xen/common/xsplice.c
index 72a3b88..11b19dd 100644
--- a/xen/common/xsplice.c
+++ b/xen/common/xsplice.c
@@ -123,6 +123,35 @@ static int verify_payload(const 
xen_sysctl_xsplice_upload_t *upload, char *n)
     return 0;
 }
 
+bool_t is_patch(const void *ptr)
+{
+    const struct payload *data;
+    bool_t r = 0;
+
+    /*
+     * Only RCU locking since this list is only ever changed during apply
+     * or revert context. And in case it dies there we need an safe list.
+     */
+    rcu_read_lock(&rcu_applied_lock);
+    list_for_each_entry_rcu ( data, &applied_list, applied_list )
+    {
+        if ( (ptr >= data->rw_addr &&
+              ptr < (data->rw_addr + data->rw_size)) ||
+             (ptr >= data->ro_addr &&
+              ptr < (data->ro_addr + data->ro_size)) ||
+             (ptr >= data->text_addr &&
+              ptr < (data->text_addr + data->text_size)) )
+        {
+            r = 1;
+            break;
+        }
+
+    }
+    rcu_read_unlock(&rcu_applied_lock);
+
+    return r;
+}
+
 void *xsplice_symbols_lookup_by_name(const char *symname)
 {
     const struct payload *data;
@@ -482,6 +511,28 @@ static int prepare_payload(struct payload *payload,
     region->start = payload->text_addr;
     region->end = payload->text_addr + payload->text_size;
 
+    /* Optional sections. */
+    for ( i = 0; i < BUGFRAME_NR; i++ )
+    {
+        char str[14];
+
+        snprintf(str, sizeof(str), ".bug_frames.%u", i);
+        sec = xsplice_elf_sec_by_name(elf, str);
+        if ( !sec )
+            continue;
+
+        if ( sec->sec->sh_size % sizeof(*region->frame[i].bugs) )
+        {
+            dprintk(XENLOG_ERR, XSPLICE "%s: Wrong size of .bug_frames.%u!\n",
+                    elf->name, i);
+            return -EINVAL;
+        }
+
+        region->frame[i].bugs = sec->load_addr;
+        region->frame[i].n_bugs = sec->sec->sh_size /
+                                  sizeof(*region->frame[i].bugs);
+    }
+
     return 0;
 }
 
diff --git a/xen/include/xen/xsplice.h b/xen/include/xen/xsplice.h
index bb8baee..7f4c8f7 100644
--- a/xen/include/xen/xsplice.h
+++ b/xen/include/xen/xsplice.h
@@ -29,6 +29,7 @@ struct xsplice_symbol {
 int xsplice_op(struct xen_sysctl_xsplice_op *);
 void check_for_xsplice_work(void);
 void *xsplice_symbols_lookup_by_name(const char *symname);
+bool_t is_patch(const void *addr);
 
 /* Arch hooks. */
 int arch_xsplice_verify_elf(const struct xsplice_elf *elf);
@@ -76,6 +77,10 @@ static inline int xsplice_op(struct xen_sysctl_xsplice_op 
*op)
 }
 
 static inline void check_for_xsplice_work(void) { };
+static inline bool_t is_patch(const void *addr)
+{
+    return 0;
+}
 #endif /* CONFIG_XSPLICE */
 
 #endif /* __XEN_XSPLICE_H__ */
-- 
2.5.0


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