[Xen-devel] [PATCH v6 3/4] xen/x86: use SYMBOL when required

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Use SYMBOL in cases of comparisons and subtractions of:

_start, _end, __2M_rwdata_start, __2M_rwdata_end, _stext, _etext,
__end_vpci_array, __start_vpci_array, _stextentry, _etextentry,
__trampoline_rel_start, __trampoline_rel_stop, __trampoline_seg_start,
__trampoline_seg_stop __per_cpu_start, __per_cpu_data_end

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 v6:
- more accurate commit message
- remove uneeded extra newline
- only use SYMBOL on problematic symbols in alternatives.c
- use new SYMBOL macro that returns the native type

Changes in v5:
- remove two spurious changes
- split into three patches
- remove SYMBOL() from derived variables
---
 xen/arch/x86/alternative.c  | 3 ++-
 xen/arch/x86/efi/efi-boot.h | 8 ++++----
 xen/arch/x86/percpu.c       | 8 ++++----
 xen/arch/x86/setup.c        | 8 +++++---
 xen/arch/x86/smpboot.c      | 5 +++--
 xen/drivers/vpci/vpci.c     | 2 +-
 6 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
index b8c819a..92c54eb 100644
--- a/xen/arch/x86/alternative.c
+++ b/xen/arch/x86/alternative.c
@@ -273,7 +273,8 @@ static int __init nmi_apply_alternatives(const struct 
cpu_user_regs *regs,
         /* Disable WP to allow patching read-only pages. */
         write_cr0(cr0 & ~X86_CR0_WP);
 
-        apply_alternatives(__alt_instructions, __alt_instructions_end);
+        apply_alternatives(SYMBOL(__alt_instructions),
+                           SYMBOL(__alt_instructions_end));
 
         write_cr0(cr0);
 
diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index 5789d2c..8dcd981 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -111,12 +111,12 @@ static void __init relocate_trampoline(unsigned long phys)
         return;
 
     /* Apply relocations to trampoline. */
-    for ( trampoline_ptr = __trampoline_rel_start;
-          trampoline_ptr < __trampoline_rel_stop;
+    for ( trampoline_ptr = SYMBOL(__trampoline_rel_start);
+          trampoline_ptr < SYMBOL(__trampoline_rel_stop);
           ++trampoline_ptr )
         *(u32 *)(*trampoline_ptr + (long)trampoline_ptr) += phys;
-    for ( trampoline_ptr = __trampoline_seg_start;
-          trampoline_ptr < __trampoline_seg_stop;
+    for ( trampoline_ptr = SYMBOL(__trampoline_seg_start);
+          trampoline_ptr < SYMBOL(__trampoline_seg_stop);
           ++trampoline_ptr )
         *(u16 *)(*trampoline_ptr + (long)trampoline_ptr) = phys >> 4;
 }
diff --git a/xen/arch/x86/percpu.c b/xen/arch/x86/percpu.c
index 8be4ebd..920bb78 100644
--- a/xen/arch/x86/percpu.c
+++ b/xen/arch/x86/percpu.c
@@ -13,7 +13,7 @@ unsigned long __per_cpu_offset[NR_CPUS];
  * context of PV guests.
  */
 #define INVALID_PERCPU_AREA (0x8000000000000000L - (long)__per_cpu_start)
-#define PERCPU_ORDER get_order_from_bytes(__per_cpu_data_end - __per_cpu_start)
+#define PERCPU_ORDER get_order_from_bytes(SYMBOL(__per_cpu_data_end) - 
SYMBOL(__per_cpu_start))
 
 void __init percpu_init_areas(void)
 {
@@ -33,8 +33,8 @@ static int init_percpu_area(unsigned int cpu)
     if ( (p = alloc_xenheap_pages(PERCPU_ORDER, 0)) == NULL )
         return -ENOMEM;
 
-    memset(p, 0, __per_cpu_data_end - __per_cpu_start);
-    __per_cpu_offset[cpu] = p - __per_cpu_start;
+    memset(p, 0, SYMBOL(__per_cpu_data_end) - SYMBOL(__per_cpu_start));
+    __per_cpu_offset[cpu] = p - SYMBOL(__per_cpu_start);
 
     return 0;
 }
@@ -49,7 +49,7 @@ static void _free_percpu_area(struct rcu_head *head)
 {
     struct free_info *info = container_of(head, struct free_info, rcu);
     unsigned int cpu = info->cpu;
-    char *p = __per_cpu_start + __per_cpu_offset[cpu];
+    char *p = SYMBOL(__per_cpu_start) + __per_cpu_offset[cpu];
 
     free_xenheap_pages(p, PERCPU_ORDER);
     __per_cpu_offset[cpu] = INVALID_PERCPU_AREA;
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 06eb483..5c35826 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -972,7 +972,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
          * respective reserve_e820_ram() invocation below.
          */
         mod[mbi->mods_count].mod_start = virt_to_mfn(_stext);
-        mod[mbi->mods_count].mod_end = __2M_rwdata_end - _stext;
+        mod[mbi->mods_count].mod_end = SYMBOL(__2M_rwdata_end) - 
SYMBOL(_stext);
     }
 
     modules_headroom = bzimage_headroom(bootstrap_map(mod), mod->mod_end);
@@ -1067,7 +1067,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
              * data until after we have switched to the relocated pagetables!
              */
             barrier();
-            move_memory(e + XEN_IMG_OFFSET, XEN_IMG_OFFSET, _end - _start, 1);
+            move_memory(e + XEN_IMG_OFFSET, XEN_IMG_OFFSET,
+                        SYMBOL(_end) - SYMBOL(_start), 1);
 
             /* Walk initial pagetables, relocating page directory entries. */
             pl4e = __va(__pa(idle_pg_table));
@@ -1382,7 +1383,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
     }
 #endif
 
-    xen_virt_end = ((unsigned long)_end + (1UL << L2_PAGETABLE_SHIFT) - 1) &
+    xen_virt_end = ((unsigned long)SYMBOL(_end) +
+                    (1UL << L2_PAGETABLE_SHIFT) - 1) &
                    ~((1UL << L2_PAGETABLE_SHIFT) - 1);
     destroy_xen_mappings(xen_virt_end, XEN_VIRT_START + BOOTSTRAP_MAP_BASE);
 
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 7d1226d..9b008b9 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -810,8 +810,9 @@ static int setup_cpu_root_pgt(unsigned int cpu)
     {
         const char *ptr;
 
-        for ( rc = 0, ptr = _stextentry;
-              !rc && ptr < _etextentry; ptr += PAGE_SIZE )
+        for ( rc = 0, ptr = SYMBOL(_stextentry);
+              !rc && ptr < SYMBOL(_etextentry);
+              ptr += PAGE_SIZE )
             rc = clone_mapping(ptr, rpt);
 
         if ( rc )
diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
index 82607bd..bc0cca6 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -33,7 +33,7 @@ struct vpci_register {
 #ifdef __XEN__
 extern vpci_register_init_t *const __start_vpci_array[];
 extern vpci_register_init_t *const __end_vpci_array[];
-#define NUM_VPCI_INIT (__end_vpci_array - __start_vpci_array)
+#define NUM_VPCI_INIT (SYMBOL(__end_vpci_array) - SYMBOL(__start_vpci_array))
 
 void vpci_remove_device(struct pci_dev *pdev)
 {
-- 
1.9.1


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