[Xen-devel] [PATCH v5 4/4] xen/common: use SYMBOL when required

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Use SYMBOL in cases of comparisons and subtractions of:

_start, _end, __init_begin, __init_end,  __2M_text_end,
__2M_rodata_start, __2M_rodata_end, __2M_init_start,__2M_init_end,
__2M_rwdata_start, __2M_rwdata_end, _stext, _etext, _srodata, _erodata,
__end_vpci_array, __start_vpci_array, _sinittext, _einittext,
_stextentry, _etextentry, __start_bug_frames, __stop_bug_frames_0,
__stop_bug_frames_1, __stop_bug_frames_2,__stop_bug_frames_3,
__note_gnu_build_id_start, __note_gnu_build_id_end, __start___ex_table,
__stop___ex_table, __start___pre_ex_table, __stop___pre_ex_table,
__lock_profile_start, __lock_profile_end, __param_start,
__param_end, __setup_start, __setup_end, __initcall_start,
__initcall_end, __presmp_initcall_end, __trampoline_rel_start,
__trampoline_rel_stop, __trampoline_seg_start, __trampoline_seg_stop
__alt_instructions, __alt_instructions_end, __ctors_start, __ctors_end,
__end_schedulers_array, __start_schedulers_array, __bss_start,
__bss_end, __per_cpu_start, __per_cpu_data_end, _splatform, _eplatform,
_sdevice, _edevice, _asdevice, _aedevice, __proc_info_start,
__proc_info_end, _sdtb


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

[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>
CC: JBeulich@xxxxxxxx
CC: andrew.cooper3@xxxxxxxxxx
---
Changes in v5:
- remove two spurious changes
- split into three patches
- remove SYMBOL() from derived variables
---
 xen/common/kernel.c         |  8 ++++++--
 xen/common/lib.c            |  2 +-
 xen/common/schedule.c       |  2 +-
 xen/common/spinlock.c       |  4 +++-
 xen/common/version.c        |  6 +++---
 xen/common/virtual_region.c |  6 +++++-
 xen/include/xen/kernel.h    | 24 ++++++++++++------------
 7 files changed, 31 insertions(+), 21 deletions(-)

diff --git a/xen/common/kernel.c b/xen/common/kernel.c
index 5766a0f..97eb648 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;
+                 (unsigned long)call < SYMBOL(__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;
+                 (unsigned long)call < SYMBOL(__initcall_end);
+                 call++ )
         (*call)();
 }
 
diff --git a/xen/common/lib.c b/xen/common/lib.c
index 8ebec81..c1d2c96 100644
--- a/xen/common/lib.c
+++ b/xen/common/lib.c
@@ -497,7 +497,7 @@ 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; (unsigned long)f < SYMBOL(__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..063086e 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -68,7 +68,7 @@ DEFINE_PER_CPU(struct scheduler *, scheduler);
 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 NUM_SCHEDULERS (SYMBOL(__end_schedulers_array) - 
SYMBOL(__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..00a3a86 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;
+                 (unsigned long)q < SYMBOL(&__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..0726c14 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 ( SYMBOL(__note_gnu_build_id_end) <= (unsigned long)&n[0] )
         return -ENODATA;
 
     /* Check for full Note header. */
-    if ( &n[1] >= __note_gnu_build_id_end )
+    if ( (unsigned long)&n[1] >= SYMBOL(__note_gnu_build_id_end) )
         return -ENODATA;
 
-    sz = (void *)__note_gnu_build_id_end - (void *)n;
+    sz = SYMBOL(__note_gnu_build_id_end) - (unsigned long)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..111c6fd 100644
--- a/xen/common/virtual_region.c
+++ b/xen/common/virtual_region.c
@@ -119,7 +119,11 @@ 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;
+        /*
+         * Cast to unsigned long to calculate the size to avoid
+         * subtractions between pointers pointing to different objects.
+         */
+        sz = (unsigned long)bug_frames[i] - (unsigned long)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..cd27030 100644
--- a/xen/include/xen/kernel.h
+++ b/xen/include/xen/kernel.h
@@ -66,27 +66,27 @@
 })
 
 extern char _start[], _end[], start[];
-#define is_kernel(p) ({                         \
-    char *__p = (char *)(unsigned long)(p);     \
-    (__p >= _start) && (__p < _end);            \
+#define is_kernel(p) ({                                             \
+    const unsigned long __p = (unsigned long)(p);                   \
+    (__p >= SYMBOL(_start)) && (__p < SYMBOL(_end));            \
 })
 
 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 unsigned long __p = (unsigned long)(p);                   \
+    (__p >= SYMBOL(_stext)) && (__p < SYMBOL(_etext));          \
 })
 
 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 unsigned long __p = (unsigned long)(p);                   \
+    (__p >= SYMBOL(_srodata)) && (__p < SYMBOL(_erodata));      \
 })
 
 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 unsigned long __p = (unsigned long)(p);                   \
+    (__p >= SYMBOL(_sinittext)) && (__p < SYMBOL(_einittext));  \
 })
 
 extern enum system_state {
-- 
1.9.1


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