[Xen-devel] [PATCH v9 5/5] xen/common: use SYMBOLS_SUBTRACT and SYMBOLS_COMPARE as required

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Use SYMBOLS_SUBTRACT and SYMBOLS_COMPARE in cases of comparisons and
subtractions of:

_start, _end, _stext, _etext, _srodata, _erodata, _sinittext,
_einittext, __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,

as by the C standard [1].

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.

[1] 
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>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
CC: JBeulich@xxxxxxxx
CC: andrew.cooper3@xxxxxxxxxx
---
Changes in v9:
- use SYMBOLS_SUBTRACT and SYMBOLS_COMPARE
---
 xen/common/kernel.c         |  8 ++++++--
 xen/common/lib.c            |  5 ++++-
 xen/common/schedule.c       |  6 ++++--
 xen/common/spinlock.c       |  4 +++-
 xen/common/version.c        |  6 +++---
 xen/common/virtual_region.c |  3 ++-
 xen/include/xen/kernel.h    | 28 ++++++++++++++++------------
 7 files changed, 38 insertions(+), 22 deletions(-)

diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index 5766a0f..b1122a1 100644
--- a/xen/common/kernel.c
+++ b/xen/common/kernel.c
@@ -312,14 +312,18 @@ extern const initcall_t __initcall_start[], 
__presmp_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;
+          SYMBOLS_COMPARE(call, __presmp_initcall_end) < 0;
+          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;
+          SYMBOLS_COMPARE(call, __initcall_end) < 0;
+          call++ )
         (*call)();
 }
 
diff --git a/xen/common/lib.c b/xen/common/lib.c
index 8ebec81..ea32367 100644
--- a/xen/common/lib.c
+++ b/xen/common/lib.c
@@ -497,7 +497,10 @@ extern const ctor_func_t __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;
+          SYMBOLS_COMPARE(f, __ctors_end) < 0;
+          ++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..0181275 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)
+extern const struct scheduler *__start_schedulers_array[],
+                              *__end_schedulers_array[];
+#define NUM_SCHEDULERS (SYMBOLS_SUBTRACT(__end_schedulers_array, \
+                                         __start_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..1fe292f 100644
--- a/xen/common/spinlock.c
+++ b/xen/common/spinlock.c
@@ -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;
+          SYMBOLS_COMPARE(q, &__lock_profile_end) < 0;
+          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..cdf2e56 100644
--- a/xen/common/version.c
+++ b/xen/common/version.c
@@ -147,14 +147,14 @@ static int __init xen_build_init(void)
     int rc;
 
     /* --build-id invoked with wrong parameters. */
-    if ( __note_gnu_build_id_end <= &n[0] )
+    if ( SYMBOLS_COMPARE(__note_gnu_build_id_end, &n[0]) <= 0 )
         return -ENODATA;
 
     /* Check for full Note header. */
-    if ( &n[1] >= __note_gnu_build_id_end )
+    if ( SYMBOLS_COMPARE(&n[1], __note_gnu_build_id_end) >= 0 )
         return -ENODATA;
 
-    sz = (void *)__note_gnu_build_id_end - (void *)n;
+    sz = SYMBOLS_SUBTRACT(__note_gnu_build_id_end, (void *)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..b3afcb9 100644
--- a/xen/common/virtual_region.c
+++ b/xen/common/virtual_region.c
@@ -119,7 +119,8 @@ 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 = SYMBOLS_SUBTRACT(bug_frames[i], s);
 
         core.frame[i - 1].n_bugs = sz;
         core.frame[i - 1].bugs = s;
diff --git a/xen/include/xen/kernel.h b/xen/include/xen/kernel.h
index 548b64d..826fc32 100644
--- a/xen/include/xen/kernel.h
+++ b/xen/include/xen/kernel.h
@@ -66,27 +66,31 @@
 })
 
 extern char _start[], _end[], start[];
-#define is_kernel(p) ({                         \
-    char *__p = (char *)(unsigned long)(p);     \
-    (__p >= _start) && (__p < _end);            \
+#define is_kernel(p) ({                                             \
+    const char *p__ = (const char *)(unsigned long)(p);             \
+    (SYMBOLS_COMPARE(p__, _start) >= 0 &&                           \
+    SYMBOLS_COMPARE(p__, _end) < 0);                                \
 })
 
 extern char _stext[], _etext[];
-#define is_kernel_text(p) ({                    \
-    char *__p = (char *)(unsigned long)(p);     \
-    (__p >= _stext) && (__p < _etext);          \
+#define is_kernel_text(p) ({                                        \
+    const char *p__ = (const char *)(unsigned long)(p);             \
+    (SYMBOLS_COMPARE(p__, _stext) >= 0 &&                           \
+    SYMBOLS_COMPARE(p__, _etext) < 0);                              \
 })
 
 extern const char _srodata[], _erodata[];
-#define is_kernel_rodata(p) ({                  \
-    const char *__p = (const char *)(unsigned long)(p);     \
-    (__p >= _srodata) && (__p < _erodata);      \
+#define is_kernel_rodata(p) ({                                      \
+    const char *p__ = (const char *)(unsigned long)(p);             \
+    (SYMBOLS_COMPARE(p__, _srodata) >= 0 &&                         \
+    SYMBOLS_COMPARE(p__, _erodata) < 0);                            \
 })
 
 extern char _sinittext[], _einittext[];
-#define is_kernel_inittext(p) ({                \
-    char *__p = (char *)(unsigned long)(p);     \
-    (__p >= _sinittext) && (__p < _einittext);  \
+#define is_kernel_inittext(p) ({                                    \
+    const char *p__ = (const char *)(unsigned long)(p);             \
+    (SYMBOLS_COMPARE(p__, _sinittext) >= 0 &&                       \
+    SYMBOLS_COMPARE(p__, _einittext) < 0);                          \
 })
 
 extern enum system_state {
-- 
1.9.1


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