[POWERPC] 4xx: Deal with 44x virtually tagged icache

The 44x family has an interesting "feature" which is a virtually
tagged instruction cache (yuck !). So far, we haven't dealt with
it properly, which means we've been mostly lucky or people didn't
report the problems, unless people have been running custom patches
in their distro...

This is an attempt at fixing it properly. I chose to do it by
setting a global flag whenever we change a PTE that was previously
marked executable, and flush the entire instruction cache upon
return to user space when that happens.

This is a bit heavy handed, but it's hard to do more fine grained
flushes as the icbi instruction, on those processor, for some very
strange reasons (since the cache is virtually mapped) still requires
a valid TLB entry for reading in the target address space, which
isn't something I want to deal with.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/include/asm-powerpc/pgtable-ppc32.h b/include/asm-powerpc/pgtable-ppc32.h
index 86a54a4a8a2a..fea2d8ff1e73 100644
--- a/include/asm-powerpc/pgtable-ppc32.h
+++ b/include/asm-powerpc/pgtable-ppc32.h
@@ -11,6 +11,11 @@
 extern unsigned long va_to_phys(unsigned long address);
 extern pte_t *va_to_pte(unsigned long address);
 extern unsigned long ioremap_bot, ioremap_base;
+
+#ifdef CONFIG_44x
+extern int icache_44x_need_flush;
+#endif
+
 #endif /* __ASSEMBLY__ */
 
 /*
@@ -562,6 +567,10 @@ static inline unsigned long pte_update(pte_t *p, unsigned long clr,
         : "=&r" (old), "=&r" (tmp), "=m" (*p)
         : "r" (p), "r" (clr), "r" (set), "m" (*p)
         : "cc" );
+#ifdef CONFIG_44x
+        if ((old & _PAGE_USER) && (old & _PAGE_HWEXEC))
+                icache_44x_need_flush = 1;
+#endif
         return old;
 }
 #else
@@ -582,6 +591,10 @@ static inline unsigned long long pte_update(pte_t *p, unsigned long clr,
         : "=&r" (old), "=&r" (tmp), "=m" (*p)
         : "r" (p), "r" ((unsigned long)(p) + 4), "r" (clr), "r" (set), "m" (*p)
         : "cc" );
+#ifdef CONFIG_44x
+        if ((old & _PAGE_USER) && (old & _PAGE_HWEXEC))
+                icache_44x_need_flush = 1;
+#endif
         return old;
 }
 #endif