[PATCH] x86_64: Support alternative() in vsyscalls

The real vsyscall .text addresses are not mapped when the alternative()
replacement runs early, so use some black magic to access them using
the direct mapping.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index e7a4d2cd3968699b79fda9d41993f9c5f7f21d48..8090a0a4688271649cb562491655b2b7983e85fe 100644 (file)
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -478,6 +478,8 @@ static unsigned char *k8_nops[ASM_NOP_MAX+1] = {
      k8nops + 1 + 2 + 3 + 4 + 5 + 6 + 7,
 }; 
 
+extern char __vsyscall_0;
+
 /* Replace instructions with better alternatives for this CPU type.
 
    This runs before SMP is initialized to avoid SMP problems with
@@ -489,11 +491,17 @@ void apply_alternatives(void *start, void *end)
        struct alt_instr *a; 
        int diff, i, k;
        for (a = start; (void *)a < end; a++) { 
+               u8 *instr;
+
                if (!boot_cpu_has(a->cpuid))
                        continue;
 
                BUG_ON(a->replacementlen > a->instrlen); 
-               __inline_memcpy(a->instr, a->replacement, a->replacementlen); 
+               instr = a->instr;
+               /* vsyscall code is not mapped yet. resolve it manually. */
+               if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END)
+                       instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0));
+               __inline_memcpy(instr, a->replacement, a->replacementlen);
                diff = a->instrlen - a->replacementlen; 
 
                /* Pad the rest with nops */
@@ -501,7 +509,7 @@ void apply_alternatives(void *start, void *end)
                        k = diff;
                        if (k > ASM_NOP_MAX)
                                k = ASM_NOP_MAX;
-                       __inline_memcpy(a->instr + i, k8_nops[k], k); 
+                       __inline_memcpy(instr + i, k8_nops[k], k);
                } 
        }
 }