x86: Add text_poke_smp for SMP cross modifying code

[deliverable/linux.git] / arch / x86 / kernel / alternative.c

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index de7353c0ce9ca5bbb029e513bd55773a6c2396d5..c41f13c15e8fcafad1b5f6ce34ac4a2e38b8c325 100644 (file)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -7,6 +7,7 @@
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <linux/memory.h>
+#include <linux/stop_machine.h>
 #include <asm/alternative.h>
 #include <asm/sections.h>
 #include <asm/pgtable.h>
@@ -390,6 +391,24 @@ void alternatives_smp_switch(int smp)
        mutex_unlock(&smp_alt);
 }
 
+/* Return 1 if the address range is reserved for smp-alternatives */
+int alternatives_text_reserved(void *start, void *end)
+{
+       struct smp_alt_module *mod;
+       u8 **ptr;
+       u8 *text_start = start;
+       u8 *text_end = end;
+
+       list_for_each_entry(mod, &smp_alt_modules, next) {
+               if (mod->text > text_end || mod->text_end < text_start)
+                       continue;
+               for (ptr = mod->locks; ptr < mod->locks_end; ptr++)
+                       if (text_start <= *ptr && text_end >= *ptr)
+                               return 1;
+       }
+
+       return 0;
+}
 #endif
 
 #ifdef CONFIG_PARAVIRT
@@ -552,3 +571,62 @@ void *__kprobes text_poke(void *addr, const void *opcode, size_t len)
        local_irq_restore(flags);
        return addr;
 }
+
+/*
+ * Cross-modifying kernel text with stop_machine().
+ * This code originally comes from immediate value.
+ */
+static atomic_t stop_machine_first;
+static int wrote_text;
+
+struct text_poke_params {
+       void *addr;
+       const void *opcode;
+       size_t len;
+};
+
+static int __kprobes stop_machine_text_poke(void *data)
+{
+       struct text_poke_params *tpp = data;
+
+       if (atomic_dec_and_test(&stop_machine_first)) {
+               text_poke(tpp->addr, tpp->opcode, tpp->len);
+               smp_wmb();      /* Make sure other cpus see that this has run */
+               wrote_text = 1;
+       } else {
+               while (!wrote_text)
+                       smp_rmb();
+               sync_core();
+       }
+
+       flush_icache_range((unsigned long)tpp->addr,
+                          (unsigned long)tpp->addr + tpp->len);
+       return 0;
+}
+
+/**
+ * text_poke_smp - Update instructions on a live kernel on SMP
+ * @addr: address to modify
+ * @opcode: source of the copy
+ * @len: length to copy
+ *
+ * Modify multi-byte instruction by using stop_machine() on SMP. This allows
+ * user to poke/set multi-byte text on SMP. Only non-NMI/MCE code modifying
+ * should be allowed, since stop_machine() does _not_ protect code against
+ * NMI and MCE.
+ *
+ * Note: Must be called under get_online_cpus() and text_mutex.
+ */
+void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len)
+{
+       struct text_poke_params tpp;
+
+       tpp.addr = addr;
+       tpp.opcode = opcode;
+       tpp.len = len;
+       atomic_set(&stop_machine_first, 1);
+       wrote_text = 0;
+       stop_machine(stop_machine_text_poke, (void *)&tpp, NULL);
+       return addr;
+}
+