[Xen-devel] [PATCH v10 5/6] xen/common: use DEFINE_SYMBOL as required

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Use DEFINE_SYMBOL and the two static inline functions that come with it
for comparisons and subtractions of:

__note_gnu_build_id_start, __note_gnu_build_id_end,
__lock_profile_start, __lock_profile_end, __initcall_start,
__initcall_end, __presmp_initcall_end, __ctors_start, __ctors_end,
__end_schedulers_array, __start_schedulers_array, __start_bug_frames,
__stop_bug_frames_0, __stop_bug_frames_1, __stop_bug_frames_2,
__stop_bug_frames_3,

Use explicit casts to uintptr_t when it is not possible to use the
provided static inline functions.

M3CM: Rule-18.2: Subtraction between pointers shall only be applied to
pointers that address elements of the same array

Since we are changing the body of is_kernel_text and friends, take the
opportunity to remove the leading underscores in the local variables
names, which are violationg namespace rules. Also make the local p__
variable const.

https://wiki.sei.cmu.edu/confluence/display/c/ARR36-C.+Do+not+subtract+or+compare+two+pointers+that+do+not+refer+to+the+same+array

QAVerify: 2761
Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>
CC: JBeulich@xxxxxxxx
CC: andrew.cooper3@xxxxxxxxxx
---
Changes in v10:
- use DEFINE_SYMBOL
- move changes for _start, _end, _stext, _etext, _srodata, _erodata,
  _sinittext, _einittext to a different patch

Changes in v9:
- use SYMBOLS_SUBTRACT and SYMBOLS_COMPARE
---
 xen/common/kernel.c         | 12 ++++++++++--
 xen/common/lib.c            |  7 +++++--
 xen/common/schedule.c       |  6 ++++--
 xen/common/spinlock.c       |  8 +++++---
 xen/common/version.c        |  9 +++++----
 xen/common/virtual_region.c |  4 +++-
 6 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index 5766a0f..f6c8d80 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -306,20 +306,28 @@ void add_taint(unsigned int flag)
     tainted |= flag;
 }
 
+/*
+ * We cannot use DEFINE_SYMBOL because we have three variables instead
+ * of two
+ */
 extern const initcall_t __initcall_start[], __presmp_initcall_end[],
     __initcall_end[];
 
 void __init do_presmp_initcalls(void)
 {
     const initcall_t *call;
-    for ( call = __initcall_start; call < __presmp_initcall_end; call++ )
+    for ( call = __initcall_start;
+          (uintptr_t)call < (uintptr_t)__presmp_initcall_end;
+          call++ )
         (*call)();
 }
 
 void __init do_initcalls(void)
 {
     const initcall_t *call;
-    for ( call = __presmp_initcall_end; call < __initcall_end; call++ )
+    for ( call = __presmp_initcall_end;
+          (uintptr_t)call < (uintptr_t)__initcall_end;
+          call++ )
         (*call)();
 }
 
diff --git a/xen/common/lib.c b/xen/common/lib.c
index 8ebec81..0b2105a 100644
--- a/xen/common/lib.c
+++ b/xen/common/lib.c
@@ -492,12 +492,15 @@ unsigned long long parse_size_and_unit(const char *s, 
const char **ps)
 }
 
 typedef void (*ctor_func_t)(void);
-extern const ctor_func_t __ctors_start[], __ctors_end[];
+DEFINE_SYMBOL(ctor_func_t, ctor_func, __ctors_start, __ctors_end);
 
 void __init init_constructors(void)
 {
     const ctor_func_t *f;
-    for ( f = __ctors_start; f < __ctors_end; ++f )
+
+    for ( f = __ctors_start;
+          ctor_func_lt(f, __ctors_end);
+          ++f )
         (*f)();
 
     /* Putting this here seems as good (or bad) as any other place. */
diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index a957c5e..ac3f9af 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -67,8 +67,10 @@ DEFINE_PER_CPU(struct scheduler *, scheduler);
 /* Scratch space for cpumasks. */
 DEFINE_PER_CPU(cpumask_t, cpumask_scratch);
 
-extern const struct scheduler *__start_schedulers_array[], 
*__end_schedulers_array[];
-#define NUM_SCHEDULERS (__end_schedulers_array - __start_schedulers_array)
+DEFINE_SYMBOL(struct scheduler *, schedulers, __start_schedulers_array,
+              __end_schedulers_array);
+#define NUM_SCHEDULERS (schedulers_diff(__start_schedulers_array, \
+                                        __end_schedulers_array))
 #define schedulers __start_schedulers_array
 
 static struct scheduler __read_mostly ops;
diff --git a/xen/common/spinlock.c b/xen/common/spinlock.c
index 6bc52d7..2d04bf8 100644
--- a/xen/common/spinlock.c
+++ b/xen/common/spinlock.c
@@ -318,8 +318,8 @@ struct lock_profile_anc {
 typedef void lock_profile_subfunc(
     struct lock_profile *, int32_t, int32_t, void *);
 
-extern struct lock_profile *__lock_profile_start;
-extern struct lock_profile *__lock_profile_end;
+DEFINE_SYMBOL(struct lock_profile *, lock_profile, __lock_profile_start,
+              __lock_profile_end);
 
 static s_time_t lock_profile_start;
 static struct lock_profile_anc lock_profile_ancs[LOCKPROF_TYPE_N];
@@ -474,7 +474,9 @@ static int __init lock_prof_init(void)
 {
     struct lock_profile **q;
 
-    for ( q = &__lock_profile_start; q < &__lock_profile_end; q++ )
+    for ( q = &__lock_profile_start;
+          lock_profile_lt(q, &__lock_profile_end);
+          q++ )
     {
         (*q)->next = lock_profile_glb_q.elem_q;
         lock_profile_glb_q.elem_q = *q;
diff --git a/xen/common/version.c b/xen/common/version.c
index 223cb52..1303fe7 100644
--- a/xen/common/version.c
+++ b/xen/common/version.c
@@ -86,7 +86,8 @@ int xen_build_id(const void **p, unsigned int *len)
 
 #ifdef BUILD_ID
 /* Defined in linker script. */
-extern const Elf_Note __note_gnu_build_id_start[], __note_gnu_build_id_end[];
+DEFINE_SYMBOL(const Elf_Note, elf_note, __note_gnu_build_id_start,
+              __note_gnu_build_id_end);
 
 int xen_build_id_check(const Elf_Note *n, unsigned int n_sz,
                        const void **p, unsigned int *len)
@@ -147,14 +148,14 @@ static int __init xen_build_init(void)
     int rc;
 
     /* --build-id invoked with wrong parameters. */
-    if ( __note_gnu_build_id_end <= &n[0] )
+    if ( !elf_note_lt(&n[0], __note_gnu_build_id_end) )
         return -ENODATA;
 
     /* Check for full Note header. */
-    if ( &n[1] >= __note_gnu_build_id_end )
+    if ( !elf_note_lt(&n[1], __note_gnu_build_id_end) )
         return -ENODATA;
 
-    sz = (void *)__note_gnu_build_id_end - (void *)n;
+    sz = (uintptr_t)__note_gnu_build_id_end - (uintptr_t)n;
 
     rc = xen_build_id_check(n, sz, &build_id_p, &build_id_len);
 
diff --git a/xen/common/virtual_region.c b/xen/common/virtual_region.c
index aa23918..87ef33a 100644
--- a/xen/common/virtual_region.c
+++ b/xen/common/virtual_region.c
@@ -119,7 +119,9 @@ void __init setup_virtual_regions(const struct 
exception_table_entry *start,
         const struct bug_frame *s;
 
         s = bug_frames[i - 1];
-        sz = bug_frames[i] - s;
+        /* bug_frame[i] and s are pointers to different objects. */
+        sz = ((uintptr_t)bug_frames[i] - (uintptr_t)s) /
+             sizeof(struct bug_frame);
 
         core.frame[i - 1].n_bugs = sz;
         core.frame[i - 1].bugs = s;
-- 
1.9.1


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