[OpenBIOS] PPC: QEMU breaks static variables in OpenBIOS

[Alexander Graf]

On 05.01.2013, at 23:26, Alexander Graf wrote:

> 
> On 05.01.2013, at 23:13, Alexander Graf wrote:
> 
>> 
>> On 05.01.2013, at 22:47, Mark Cave-Ayland wrote:
>> 
>>> On 05/01/13 21:23, Alexander Graf wrote:
>>> 
>>>>> I thought about that, but figured that because it was a hot-path I'd do it inline to save some cycles invoking another function. Since it uses the same OF_* constants as those functions then it should just work.
>>>> 
>>>> If the calculation function was provided through a static inline function in a header, this'd be a no-issue.
>>>> 
>>>> Alex
>>> 
>>> va2pa() looks like a good candidate for this, however it isn't marked as static inline because it's called from ofmem_common.c in libopenbios.
>>> 
>>> Then again I'm not sure this is important as I've heard in several places that most optimising compilers ignore the inline keyword, and will just inline whatever they think will run fastest based upon the current optimisation level.
>>> 
>>> Anyway let me know which way you'd prefer.
>> 
>> 
>> Does the patch below work?
> 
> It looks pretty broken still:

The problem is that .bss is beyond OF_CODE_START + OF_CODE_SIZE. Too bad.
This version seems to compile into something sane. It's essentially the same as Mark's latest one though, just slightly more readable IMHO :).


Alex

diff --git a/arch/ppc/qemu/ofmem.c b/arch/ppc/qemu/ofmem.c
index 25555a0..bd4e112 100644
--- a/arch/ppc/qemu/ofmem.c
+++ b/arch/ppc/qemu/ofmem.c
@@ -311,10 +311,32 @@ ea_to_phys(unsigned long ea, ucell *mode)
     return phys;
 }
 
+/* Converts a global variable (from .data or .bss) into a pointer that
+   can be accessed from real mode */
+static void *
+global_ptr_real(void *p)
+{
+    return (void*)((uintptr_t)p - OF_CODE_START + get_rom_base());
+}
+
+/* Return the next slot to evict, in the range of [0..7] */
+static int
+next_evicted_slot(void)
+{
+    static int next_grab_slot;
+    int *next_grab_slot_va;
+    int r;
+
+    next_grab_slot_va = global_ptr_real(&next_grab_slot);
+    r = *next_grab_slot_va;
+    *next_grab_slot_va = (r + 1) % 8;
+
+    return r;
+}
+
 static void
 hash_page_64(unsigned long ea, phys_addr_t phys, ucell mode)
 {
-    static int next_grab_slot = 0;
     uint64_t vsid_mask, page_mask, pgidx, hash;
     uint64_t htab_mask, mask, avpn;
     unsigned long pgaddr;
@@ -349,10 +371,8 @@ hash_page_64(unsigned long ea, phys_addr_t phys, ucell mode)
             found = 1;
 
     /* out of slots, just evict one */
-    if (!found) {
-        i = next_grab_slot + 1;
-        next_grab_slot = (next_grab_slot + 1) % 8;
-    }
+    if (!found)
+        i = next_evicted_slot() + 1;
     i--;
     {
     mPTE_64_t p = {
@@ -381,7 +401,6 @@ static void
 hash_page_32(unsigned long ea, phys_addr_t phys, ucell mode)
 {
 #ifndef __powerpc64__
-    static int next_grab_slot = 0;
     unsigned long *upte, cmp, hash1;
     int i, vsid, found;
     mPTE_t *pp;
@@ -407,10 +426,8 @@ hash_page_32(unsigned long ea, phys_addr_t phys, ucell mode)
             found = 1;
 
     /* out of slots, just evict one */
-    if (!found) {
-        i = next_grab_slot + 1;
-        next_grab_slot = (next_grab_slot + 1) % 8;
-    }
+    if (!found)
+        i = next_evicted_slot() + 1;
     i--;
     upte[i * 2] = cmp;
     upte[i * 2 + 1] = (phys & ~0xfff) | mode;