linux/arch/powerpc/kernel/ftrace.c

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/*
* Code for replacing ftrace calls with jumps.
*
* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
*
* Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
*
*/
#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 = 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)
#endif
static unsigned int ftrace_calc_offset(long ip, long addr)
{
return (int)(addr - ip);
}
static unsigned char *ftrace_nop_replace(void)
{
return (char *)&ftrace_nop;
}
static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
{
static unsigned int op;
/*
* It would be nice to just use create_function_call, but that will
* update the code itself. Here we need to just return the
* instruction that is going to be modified, without modifying the
* code.
*/
addr = GET_ADDR(addr);
/* Set to "bl addr" */
op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
/*
* No locking needed, this must be called via kstop_machine
* which in essence is like running on a uniprocessor machine.
*/
return (unsigned char *)&op;
}
#ifdef CONFIG_PPC64
# define _ASM_ALIGN " .align 3 "
# define _ASM_PTR " .llong "
#else
# define _ASM_ALIGN " .align 2 "
# define _ASM_PTR " .long "
#endif
static int
ftrace_modify_code(unsigned long ip, unsigned char *old_code,
unsigned char *new_code)
{
unsigned char replaced[MCOUNT_INSN_SIZE];
/*
* Note: Due to modules and __init, code can
* disappear and change, we need to protect against faulting
* as well as code changing. We do this by using the
* probe_kernel_* functions.
*
* No real locking needed, this code is run through
* kstop_machine, or before SMP starts.
*/
/* read the text we want to modify */
if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))
return -EFAULT;
/* Make sure it is what we expect it to be */
if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
return -EINVAL;
/* replace the text with the new text */
if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
return -EPERM;
flush_icache_range(ip, ip + 8);
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;
/*
* Can we get to addr from ip in 24 bits?
* (26 really, since we mulitply by 4 for 4 byte alignment)
*/
diff = addr - ip;
/*
* Return true if diff is less than 1 << 25
* and greater than -1 << 26.
*/
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(ip, addr)) {
/* within range */
old = ftrace_call_replace(ip, addr);
new = ftrace_nop_replace();
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(ip, addr)) {
/* within range */
old = ftrace_nop_replace();
new = ftrace_call_replace(ip, 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
* 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)
{
unsigned long ip = (unsigned long)(&ftrace_call);
unsigned char old[MCOUNT_INSN_SIZE], *new;
int ret;
memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
new = ftrace_call_replace(ip, (unsigned long)func);
ret = ftrace_modify_code(ip, old, new);
return ret;
}
int __init ftrace_dyn_arch_init(void *data)
{
/* caller expects data to be zero */
unsigned long *p = data;
*p = 0;
return 0;
}