1 files changed, 268 insertions, 10 deletions

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 1adfbb268d8e..1aec559bdfcb 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -10,22 +10,29 @@
 #include <linux/spinlock.h>
 #include <linux/hardirq.h>
 #include <linux/uaccess.h>
+#include <linux/module.h>
 #include <linux/ftrace.h>
 #include <linux/percpu.h>
 #include <linux/init.h>
 #include <linux/list.h>
 
 #include <asm/cacheflush.h>
+#include <asm/code-patching.h>
 #include <asm/ftrace.h>
 
+#if 0
+#define DEBUGP printk
+#else
+#define DEBUGP(fmt , ...)       do { } while (0)
+#endif
 
-static unsigned int ftrace_nop = 0x60000000;
+static unsigned int ftrace_nop = PPC_NOP_INSTR;
 
 #ifdef CONFIG_PPC32
 # define GET_ADDR(addr) addr
 #else
 /* PowerPC64's functions are data that points to the functions */
-# define GET_ADDR(addr) *(unsigned long *)addr
+# define GET_ADDR(addr) (*(unsigned long *)addr)
 #endif
 
 
@@ -102,6 +109,9 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
         return 0;
 }
 
+/*
+ * Helper functions that are the same for both PPC64 and PPC32.
+ */
 static int test_24bit_addr(unsigned long ip, unsigned long addr)
 {
         long diff;
@@ -119,43 +129,292 @@ static int test_24bit_addr(unsigned long ip, unsigned long addr)
         return (diff < (1 << 25)) && (diff > (-1 << 26));
 }
 
+static int is_bl_op(unsigned int op)
+{
+        return (op & 0xfc000003) == 0x48000001;
+}
+
+static int test_offset(unsigned long offset)
+{
+        return (offset + 0x2000000 > 0x3ffffff) || ((offset & 3) != 0);
+}
+
+static unsigned long find_bl_target(unsigned long ip, unsigned int op)
+{
+        static int offset;
+
+        offset = (op & 0x03fffffc);
+        /* make it signed */
+        if (offset & 0x02000000)
+                offset |= 0xfe000000;
+
+        return ip + (long)offset;
+}
+
+static unsigned int branch_offset(unsigned long offset)
+{
+        /* return "bl ip+offset" */
+        return 0x48000001 | (offset & 0x03fffffc);
+}
+
+#ifdef CONFIG_PPC64
+static int
+__ftrace_make_nop(struct module *mod,
+                  struct dyn_ftrace *rec, unsigned long addr)
+{
+        unsigned char replaced[MCOUNT_INSN_SIZE * 2];
+        unsigned int *op = (unsigned *)&replaced;
+        unsigned char jmp[8];
+        unsigned long *ptr = (unsigned long *)&jmp;
+        unsigned long ip = rec->ip;
+        unsigned long tramp;
+        int offset;
+
+        /* read where this goes */
+        if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
+                return -EFAULT;
+
+        /* Make sure that that this is still a 24bit jump */
+        if (!is_bl_op(*op)) {
+                printk(KERN_ERR "Not expected bl: opcode is %x\n", *op);
+                return -EINVAL;
+        }
+
+        /* lets find where the pointer goes */
+        tramp = find_bl_target(ip, *op);
+
+        /*
+         * On PPC64 the trampoline looks like:
+         * 0x3d, 0x82, 0x00, 0x00,    addis   r12,r2, <high>
+         * 0x39, 0x8c, 0x00, 0x00,    addi    r12,r12, <low>
+         *   Where the bytes 2,3,6 and 7 make up the 32bit offset
+         *   to the TOC that holds the pointer.
+         *   to jump to.
+         * 0xf8, 0x41, 0x00, 0x28,    std     r2,40(r1)
+         * 0xe9, 0x6c, 0x00, 0x20,    ld      r11,32(r12)
+         *   The actually address is 32 bytes from the offset
+         *   into the TOC.
+         * 0xe8, 0x4c, 0x00, 0x28,    ld      r2,40(r12)
+         */
+
+        DEBUGP("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);
+
+        /* Find where the trampoline jumps to */
+        if (probe_kernel_read(jmp, (void *)tramp, 8)) {
+                printk(KERN_ERR "Failed to read %lx\n", tramp);
+                return -EFAULT;
+        }
+
+        DEBUGP(" %08x %08x",
+               (unsigned)(*ptr >> 32),
+               (unsigned)*ptr);
+
+        offset = (unsigned)jmp[2] << 24 |
+                (unsigned)jmp[3] << 16 |
+                (unsigned)jmp[6] << 8 |
+                (unsigned)jmp[7];
+
+        DEBUGP(" %x ", offset);
+
+        /* get the address this jumps too */
+        tramp = mod->arch.toc + offset + 32;
+        DEBUGP("toc: %lx", tramp);
+
+        if (probe_kernel_read(jmp, (void *)tramp, 8)) {
+                printk(KERN_ERR "Failed to read %lx\n", tramp);
+                return -EFAULT;
+        }
+
+        DEBUGP(" %08x %08x\n",
+               (unsigned)(*ptr >> 32),
+               (unsigned)*ptr);
+
+        /* This should match what was called */
+        if (*ptr != GET_ADDR(addr)) {
+                printk(KERN_ERR "addr does not match %lx\n", *ptr);
+                return -EINVAL;
+        }
+
+        /*
+         * We want to nop the line, but the next line is
+         *  0xe8, 0x41, 0x00, 0x28   ld r2,40(r1)
+         * This needs to be turned to a nop too.
+         */
+        if (probe_kernel_read(replaced, (void *)(ip+4), MCOUNT_INSN_SIZE))
+                return -EFAULT;
+
+        if (*op != 0xe8410028) {
+                printk(KERN_ERR "Next line is not ld! (%08x)\n", *op);
+                return -EINVAL;
+        }
+
+        /*
+         * Milton Miller pointed out that we can not blindly do nops.
+         * If a task was preempted when calling a trace function,
+         * the nops will remove the way to restore the TOC in r2
+         * and the r2 TOC will get corrupted.
+         */
+
+        /*
+         * Replace:
+         *   bl <tramp>  <==== will be replaced with "b 1f"
+         *   ld r2,40(r1)
+         *  1:
+         */
+        op[0] = 0x48000008;     /* b +8 */
+
+        if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))
+                return -EPERM;
+
+        return 0;
+}
+
+#else /* !PPC64 */
+static int
+__ftrace_make_nop(struct module *mod,
+                  struct dyn_ftrace *rec, unsigned long addr)
+{
+        /* Ignore modules for PPC32 (for now) */
+        return 0;
+}
+#endif /* PPC64 */
+
 int ftrace_make_nop(struct module *mod,
                     struct dyn_ftrace *rec, unsigned long addr)
 {
         unsigned char *old, *new;
+        unsigned long ip = rec->ip;
 
         /*
          * If the calling address is more that 24 bits away,
          * then we had to use a trampoline to make the call.
          * Otherwise just update the call site.
          */
-        if (test_24bit_addr(rec->ip, addr)) {
+        if (test_24bit_addr(ip, addr)) {
                 /* within range */
-                old = ftrace_call_replace(rec->ip, addr);
+                old = ftrace_call_replace(ip, addr);
                 new = ftrace_nop_replace();
-                return ftrace_modify_code(rec->ip, old, new);
+                return ftrace_modify_code(ip, old, new);
+        }
+
+#ifdef CONFIG_PPC64
+        /*
+         * Out of range jumps are called from modules.
+         * We should either already have a pointer to the module
+         * or it has been passed in.
+         */
+        if (!rec->arch.mod) {
+                if (!mod) {
+                        printk(KERN_ERR "No module loaded addr=%lx\n",
+                               addr);
+                        return -EFAULT;
+                }
+                rec->arch.mod = mod;
+        } else if (mod) {
+                if (mod != rec->arch.mod) {
+                        printk(KERN_ERR
+                               "Record mod %p not equal to passed in mod %p\n",
+                               rec->arch.mod, mod);
+                        return -EINVAL;
+                }
+                /* nothing to do if mod == rec->arch.mod */
+        } else
+                mod = rec->arch.mod;
+#endif /* CONFIG_PPC64 */
+
+        return __ftrace_make_nop(mod, rec, addr);
+
+}
+
+#ifdef CONFIG_PPC64
+static int
+__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+        unsigned char replaced[MCOUNT_INSN_SIZE * 2];
+        unsigned int *op = (unsigned *)&replaced;
+        unsigned long ip = rec->ip;
+        unsigned long offset;
+
+        /* read where this goes */
+        if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE * 2))
+                return -EFAULT;
+
+        /*
+         * It should be pointing to two nops or
+         *  b +8; ld r2,40(r1)
+         */
+        if (((op[0] != 0x48000008) || (op[1] != 0xe8410028)) &&
+            ((op[0] != PPC_NOP_INSTR) || (op[1] != PPC_NOP_INSTR))) {
+                printk(KERN_ERR "Expected NOPs but have %x %x\n", op[0], op[1]);
+                return -EINVAL;
+        }
+
+        /* If we never set up a trampoline to ftrace_caller, then bail */
+        if (!rec->arch.mod->arch.tramp) {
+                printk(KERN_ERR "No ftrace trampoline\n");
+                return -EINVAL;
+        }
+
+        /* now calculate a jump to the ftrace caller trampoline */
+        offset = rec->arch.mod->arch.tramp - ip;
+
+        if (test_offset(offset)) {
+                printk(KERN_ERR "REL24 %li out of range!\n",
+                       (long int)offset);
+                return -EINVAL;
         }
 
+        /* Set to "bl addr" */
+        op[0] = branch_offset(offset);
+        /* ld r2,40(r1) */
+        op[1] = 0xe8410028;
+
+        DEBUGP("write to %lx\n", rec->ip);
+
+        if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE * 2))
+                return -EPERM;
+
         return 0;
 }
+#else
+static int
+__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+        /* PPC32 ignores modules for now */
+        return 0;
+}
+#endif /* CONFIG_PPC64 */
 
 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
         unsigned char *old, *new;
+        unsigned long ip = rec->ip;
 
         /*
          * If the calling address is more that 24 bits away,
          * then we had to use a trampoline to make the call.
          * Otherwise just update the call site.
          */
-        if (test_24bit_addr(rec->ip, addr)) {
+        if (test_24bit_addr(ip, addr)) {
                 /* within range */
                 old = ftrace_nop_replace();
-                new = ftrace_call_replace(rec->ip, addr);
-                return ftrace_modify_code(rec->ip, old, new);
+                new = ftrace_call_replace(ip, addr);
+                return ftrace_modify_code(ip, old, new);
         }
 
-        return 0;
+#ifdef CONFIG_PPC64
+        /*
+         * Out of range jumps are called from modules.
+         * Being that we are converting from nop, it had better
+         * already have a module defined.
+         */
+        if (!rec->arch.mod) {
+                printk(KERN_ERR "No module loaded\n");
+                return -EINVAL;
+        }
+#endif
+
+        return __ftrace_make_call(rec, addr);
 }
 
 int ftrace_update_ftrace_func(ftrace_func_t func)
@@ -180,4 +439,3 @@ int __init ftrace_dyn_arch_init(void *data)
 
         return 0;
 }
-