1 files changed, 107 insertions, 18 deletions

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index de7353c0ce9c..f65ab8b014c4 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -7,6 +7,8 @@
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <linux/memory.h>
+#include <linux/stop_machine.h>
+#include <linux/slab.h>
 #include <asm/alternative.h>
 #include <asm/sections.h>
 #include <asm/pgtable.h>
@@ -192,7 +194,7 @@ static void __init_or_module add_nops(void *insns, unsigned int len)
 }
 
 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
-extern u8 *__smp_locks[], *__smp_locks_end[];
+extern s32 __smp_locks[], __smp_locks_end[];
 static void *text_poke_early(void *addr, const void *opcode, size_t len);
 
 /* Replace instructions with better alternatives for this CPU type.
@@ -205,13 +207,14 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
                                          struct alt_instr *end)
 {
         struct alt_instr *a;
-        char insnbuf[MAX_PATCH_LEN];
+        u8 insnbuf[MAX_PATCH_LEN];
 
         DPRINTK("%s: alt table %p -> %p\n", __func__, start, end);
         for (a = start; a < end; a++) {
                 u8 *instr = a->instr;
                 BUG_ON(a->replacementlen > a->instrlen);
                 BUG_ON(a->instrlen > sizeof(insnbuf));
+                BUG_ON(a->cpuid >= NCAPINTS*32);
                 if (!boot_cpu_has(a->cpuid))
                         continue;
 #ifdef CONFIG_X86_64
@@ -223,6 +226,8 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
                 }
 #endif
                 memcpy(insnbuf, a->replacement, a->replacementlen);
+                if (*insnbuf == 0xe8 && a->replacementlen == 5)
+                    *(s32 *)(insnbuf + 1) += a->replacement - a->instr;
                 add_nops(insnbuf + a->replacementlen,
                          a->instrlen - a->replacementlen);
                 text_poke_early(instr, insnbuf, a->instrlen);
@@ -231,37 +236,41 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
 
 #ifdef CONFIG_SMP
 
-static void alternatives_smp_lock(u8 **start, u8 **end, u8 *text, u8 *text_end)
+static void alternatives_smp_lock(const s32 *start, const s32 *end,
+                                  u8 *text, u8 *text_end)
 {
-        u8 **ptr;
+        const s32 *poff;
 
         mutex_lock(&text_mutex);
-        for (ptr = start; ptr < end; ptr++) {
-                if (*ptr < text)
-                        continue;
-                if (*ptr > text_end)
+        for (poff = start; poff < end; poff++) {
+                u8 *ptr = (u8 *)poff + *poff;
+
+                if (!*poff || ptr < text || ptr >= text_end)
                         continue;
                 /* turn DS segment override prefix into lock prefix */
-                text_poke(*ptr, ((unsigned char []){0xf0}), 1);
+                if (*ptr == 0x3e)
+                        text_poke(ptr, ((unsigned char []){0xf0}), 1);
         };
         mutex_unlock(&text_mutex);
 }
 
-static void alternatives_smp_unlock(u8 **start, u8 **end, u8 *text, u8 *text_end)
+static void alternatives_smp_unlock(const s32 *start, const s32 *end,
+                                    u8 *text, u8 *text_end)
 {
-        u8 **ptr;
+        const s32 *poff;
 
         if (noreplace_smp)
                 return;
 
         mutex_lock(&text_mutex);
-        for (ptr = start; ptr < end; ptr++) {
-                if (*ptr < text)
-                        continue;
-                if (*ptr > text_end)
+        for (poff = start; poff < end; poff++) {
+                u8 *ptr = (u8 *)poff + *poff;
+
+                if (!*poff || ptr < text || ptr >= text_end)
                         continue;
                 /* turn lock prefix into DS segment override prefix */
-                text_poke(*ptr, ((unsigned char []){0x3E}), 1);
+                if (*ptr == 0xf0)
+                        text_poke(ptr, ((unsigned char []){0x3E}), 1);
         };
         mutex_unlock(&text_mutex);
 }
@@ -272,8 +281,8 @@ struct smp_alt_module {
         char            *name;
 
         /* ptrs to lock prefixes */
-        u8              **locks;
-        u8              **locks_end;
+        const s32       *locks;
+        const s32       *locks_end;
 
         /* .text segment, needed to avoid patching init code ;) */
         u8              *text;
@@ -390,6 +399,27 @@ 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;
+        const s32 *poff;
+        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 (poff = mod->locks; poff < mod->locks_end; poff++) {
+                        const u8 *ptr = (const u8 *)poff + *poff;
+
+                        if (text_start <= ptr && text_end > ptr)
+                                return 1;
+                }
+        }
+
+        return 0;
+}
 #endif
 
 #ifdef CONFIG_PARAVIRT
@@ -552,3 +582,62 @@ 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)
+                        cpu_relax();
+                smp_mb();       /* Load wrote_text before following execution */
+        }
+
+        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;
+}
+