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Subject[PATCH 7/7] ftrace,ppc32: dynamic ftrace to handle modules
Impact: enable modules for dynamic ftrace on PPC32

This patch performs the necessary trampoline calls to handle
modules with dynamic ftrace.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
arch/powerpc/include/asm/ftrace.h | 1 -
arch/powerpc/include/asm/module.h | 5 +-
arch/powerpc/kernel/ftrace.c | 219 +++++++++++++++++++++++++++++++-----
arch/powerpc/kernel/module_32.c | 10 ++
4 files changed, 202 insertions(+), 33 deletions(-)

diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index d57f5bc..e5f2ae8 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -17,7 +17,6 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)

struct dyn_arch_ftrace {
struct module *mod;
- unsigned long tramp;
};
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* __ASSEMBLY__ */
diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h
index 340bc69..0845488 100644
--- 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 acbec66..57fdda8 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -119,36 +119,20 @@ static int test_24bit_addr(unsigned long ip, unsigned long addr)
return !(diff & ((unsigned long)-1 << 24));
}

-int ftrace_make_nop(struct module *mod,
- struct dyn_ftrace *rec, unsigned long addr)
+#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 char *old, *new;
unsigned long ip = rec->ip;
unsigned long tramp;
int offset;

/*
- * 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(ip, addr)) {
- /* within range */
- old = ftrace_call_replace(ip, addr);
- new = ftrace_nop_replace();
- return ftrace_modify_code(ip, old, new);
- }
-
-#ifndef CONFIG_PPC64
- /* only supported for PPC64 for now */
- return 0;
-#else
-
- /*
* Out of range jumps are called from modules.
* We should either already have a pointer to the module
* or it has been passed in.
@@ -258,16 +242,105 @@ int ftrace_make_nop(struct module *mod,
return -EPERM;

return 0;
-#endif /* CONFIG_PPC64 */
}

-int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+#else /* !PPC64 */
+static int
+__ftrace_make_nop(struct module *mod,
+ struct dyn_ftrace *rec, unsigned long addr)
{
- unsigned char replaced[MCOUNT_INSN_SIZE * 2];
+ 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;
+
+ /*
+ * 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) {
+ printk(KERN_ERR
+ "Record mod %p not equal to passed in mod %p\n",
+ rec->arch.mod, mod);
+ return -EINVAL;
+ } else
+ mod = rec->arch.mod;
+
+ /* 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 ((*op & 0xff000000) != 0x48000000) {
+ printk(KERN_ERR "Not expected bl: opcode is %x\n", *op);
+ return -EINVAL;
+ }
+
+ /* lets find where the pointer goes */
+ offset = (*op & 0x03fffffc);
+ /* make it signed */
+ if (offset & 0x02000000)
+ offset |= 0xfe000000;
+
+ tramp = ip + (long)offset;
+
+ /*
+ * 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 */
+
+int ftrace_make_nop(struct module *mod,
+ struct dyn_ftrace *rec, unsigned long addr)
+{
unsigned char *old, *new;
unsigned long ip = rec->ip;
- unsigned long offset;

/*
* If the calling address is more that 24 bits away,
@@ -276,15 +349,23 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
*/
if (test_24bit_addr(ip, addr)) {
/* within range */
- old = ftrace_nop_replace();
- new = ftrace_call_replace(ip, addr);
+ old = ftrace_call_replace(ip, addr);
+ new = ftrace_nop_replace();
return ftrace_modify_code(ip, old, new);
}

-#ifndef CONFIG_PPC64
- /* only supported for PPC64 for now */
- return 0;
-#else
+ 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;

/*
* Out of range jumps are called from modules.
@@ -334,7 +415,83 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
return -EPERM;

return 0;
-#endif /* CONFIG_PPC64 */
+}
+#else
+static int
+__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+ unsigned char replaced[MCOUNT_INSN_SIZE];
+ unsigned int *op = (unsigned *)&replaced;
+ unsigned long ip = rec->ip;
+ unsigned long offset;
+
+ /*
+ * 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;
+ }
+
+ /* 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 (offset + 0x2000000 > 0x3ffffff || (offset & 3) != 0) {
+ printk(KERN_ERR "REL24 %li out of range!\n",
+ (long int)offset);
+ return -EINVAL;
+ }
+
+
+ /* Set to "bl addr" */
+ op[0] = 0x48000001 | (offset & 0x03fffffc);
+
+ DEBUGP("write to %lx\n", rec->ip);
+
+ if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))
+ return -EPERM;
+
+ return 0;
+}
+#endif
+
+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(ip, addr)) {
+ /* within range */
+ old = ftrace_nop_replace();
+ new = ftrace_call_replace(ip, addr);
+ return ftrace_modify_code(ip, old, new);
+ }
+
+ return __ftrace_make_call(rec, addr);
+
}

int ftrace_update_ftrace_func(ftrace_func_t func)
diff --git a/arch/powerpc/kernel/module_32.c b/arch/powerpc/kernel/module_32.c
index 2df91a0..f832773 100644
--- 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;
}
--
1.5.6.5
--


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