powerpc/ppc32: ftrace, dynamic ftrace to handle modules

Impact: add ability to trace modules on 32 bit PowerPC

This patch performs the necessary trampoline calls to handle
modules with dynamic ftrace on 32 bit PowerPC.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
index 340bc69..0845488 100644 (file)
--- a/arch/powerpc/include/asm/module.h
+++ b/arch/powerpc/include/asm/module.h
@@ -39,11 +39,14 @@ struct mod_arch_specific {
        unsigned long tramp;
 #endif
 
-#else
+#else /* powerpc64 */
        /* Indices of PLT sections within module. */
        unsigned int core_plt_section;
        unsigned int init_plt_section;
+#ifdef CONFIG_DYNAMIC_FTRACE
+       unsigned long tramp;
 #endif
+#endif /* powerpc64 */
 
        /* List of BUG addresses, source line numbers and filenames */
        struct list_head bug_list;

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index 1aec559..3271cd6 100644 (file)
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -274,7 +274,63 @@ static int
 __ftrace_make_nop(struct module *mod,
                  struct dyn_ftrace *rec, unsigned long addr)
 {
-       /* Ignore modules for PPC32 (for now) */
+       unsigned char replaced[MCOUNT_INSN_SIZE];
+       unsigned int *op = (unsigned *)&replaced;
+       unsigned char jmp[8];
+       unsigned int *ptr = (unsigned int *)&jmp;
+       unsigned long ip = rec->ip;
+       unsigned long tramp;
+       int offset;
+
+       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 PPC32 the trampoline looks like:
+        * lis r11,sym@ha
+        * addi r11,r11,sym@l
+        * mtctr r11
+        * bctr
+        */
+
+       DEBUGP("ip:%lx jumps to %lx", ip, tramp);
+
+       /* 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 ", ptr[0], ptr[1]);
+
+       tramp = (ptr[1] & 0xffff) |
+               ((ptr[0] & 0xffff) << 16);
+       if (tramp & 0x8000)
+               tramp -= 0x10000;
+
+       DEBUGP(" %x ", tramp);
+
+       if (tramp != addr) {
+               printk(KERN_ERR
+                      "Trampoline location %08lx does not match addr\n",
+                      tramp);
+               return -EINVAL;
+       }
+
+       op[0] = PPC_NOP_INSTR;
+
+       if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))
+               return -EPERM;
+
        return 0;
 }
 #endif /* PPC64 */
@@ -297,7 +353,6 @@ int ftrace_make_nop(struct module *mod,
                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
@@ -320,7 +375,6 @@ int ftrace_make_nop(struct module *mod,
                /* nothing to do if mod == rec->arch.mod */
        } else
                mod = rec->arch.mod;
-#endif /* CONFIG_PPC64 */
 
        return __ftrace_make_nop(mod, rec, addr);
 
@@ -380,7 +434,44 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 static int
 __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
-       /* PPC32 ignores modules for now */
+       unsigned char replaced[MCOUNT_INSN_SIZE];
+       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))
+               return -EFAULT;
+
+       /* It should be pointing to a nop */
+       if (op[0] != PPC_NOP_INSTR) {
+               printk(KERN_ERR "Expected NOP but have %x\n", op[0]);
+               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);
+
+       DEBUGP("write to %lx\n", rec->ip);
+
+       if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))
+               return -EPERM;
+
        return 0;
 }
 #endif /* CONFIG_PPC64 */
@@ -402,7 +493,6 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
                return ftrace_modify_code(ip, old, new);
        }
 
-#ifdef CONFIG_PPC64
        /*
         * Out of range jumps are called from modules.
         * Being that we are converting from nop, it had better
@@ -412,7 +502,6 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
                printk(KERN_ERR "No module loaded\n");
                return -EINVAL;
        }
-#endif
 
        return __ftrace_make_call(rec, addr);
 }

diff --git a/arch/powerpc/kernel/module_32.c b/arch/powerpc/kernel/module_32.c
index 2df91a0..f832773 100644 (file)
--- a/arch/powerpc/kernel/module_32.c
+++ b/arch/powerpc/kernel/module_32.c
@@ -22,6 +22,7 @@
 #include <linux/fs.h>
 #include <linux/string.h>
 #include <linux/kernel.h>
+#include <linux/ftrace.h>
 #include <linux/cache.h>
 #include <linux/bug.h>
 #include <linux/sort.h>
@@ -53,6 +54,9 @@ static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
                        r_addend = rela[i].r_addend;
                }
 
+#ifdef CONFIG_DYNAMIC_FTRACE
+       _count_relocs++;        /* add one for ftrace_caller */
+#endif
        return _count_relocs;
 }
 
@@ -306,5 +310,11 @@ int apply_relocate_add(Elf32_Shdr *sechdrs,
                        return -ENOEXEC;
                }
        }
+#ifdef CONFIG_DYNAMIC_FTRACE
+       module->arch.tramp =
+               do_plt_call(module->module_core,
+                           (unsigned long)ftrace_caller,
+                           sechdrs, module);
+#endif
        return 0;
 }