/*
* 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.
*
* Added function graph tracer code, taken from x86 that was written
* by Frederic Weisbecker, and ported to PPC by Steven Rostedt.
*
*/
#define pr_fmt(fmt) "ftrace-powerpc: " fmt
#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>
#include <asm/syscall.h>
#ifdef CONFIG_DYNAMIC_FTRACE
static unsigned int
ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
{
unsigned int op;
addr = ppc_function_entry((void *)addr);
/* if (link) set op to 'bl' else 'b' */
op = create_branch((unsigned int *)ip, addr, link ? 1 : 0);
return op;
}
static int
ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
{
unsigned int replaced;
/*
* 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 (replaced != old)
return -EINVAL;
/* replace the text with the new text */
if (patch_instruction((unsigned int *)ip, new))
return -EPERM;
return 0;
}
/*
* Helper functions that are the same for both PPC64 and PPC32.
*/
static int test_24bit_addr(unsigned long ip, unsigned long addr)
{
addr = ppc_function_entry((void *)addr);
/* use the create_branch to verify that this offset can be branched */
return create_branch((unsigned int *)ip, addr, 0);
}
#ifdef CONFIG_MODULES
static int is_bl_op(unsigned int op)
{
return (op & 0xfc000003) == 0x48000001;
}
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;
}
#ifdef CONFIG_PPC64
static int
__ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int op;
unsigned long entry, ptr;
unsigned long ip = rec->ip;
void *tramp;
/* read where this goes */
if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
return -EFAULT;
/* Make sure that that this is still a 24bit jump */
if (!is_bl_op(op)) {
pr_err("Not expected bl: opcode is %x\n", op);
return -EINVAL;
}
/* lets find where the pointer goes */
tramp = (void *)find_bl_target(ip, op);
pr_devel("ip:%lx jumps to %p", ip, tramp);
if (!is_module_trampoline(tramp)) {
pr_err("Not a trampoline\n");
return -EINVAL;
}
if (module_trampoline_target(mod, tramp, &ptr)) {
pr_err("Failed to get trampoline target\n");
return -EFAULT;
}
pr_devel("trampoline target %lx", ptr);
entry = ppc_global_function_entry((void *)addr);
/* This should match what was called */
if (ptr != entry) {
pr_err("addr %lx does not match expected %lx\n", ptr, entry);
return -EINVAL;
}
/*
* Our original call site looks like:
*
* bl <tramp>
* ld r2,XX(r1)
*
* Milton Miller pointed out that we can not simply nop the branch.
* 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.
*
* Use a b +8 to jump over the load.
*/
op = 0x48000008; /* b +8 */
if (patch_instruction((unsigned int *)ip, op))
return -EPERM;
return 0;
}
#else /* !PPC64 */
static int
__ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int op;
unsigned int jmp[4];
unsigned long ip = rec->ip;
unsigned long tramp;
if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
return -EFAULT;
/* Make sure that that this is still a 24bit jump */
if (!is_bl_op(op)) {
pr_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:
* 0x3d, 0x80, 0x00, 0x00 lis r12,sym@ha
* 0x39, 0x8c, 0x00, 0x00 addi r12,r12,sym@l
* 0x7d, 0x89, 0x03, 0xa6 mtctr r12
* 0x4e, 0x80, 0x04, 0x20 bctr
*/
pr_devel("ip:%lx jumps to %lx", ip, tramp);
/* Find where the trampoline jumps to */
if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
pr_err("Failed to read %lx\n", tramp);
return -EFAULT;
}
pr_devel(" %08x %08x ", jmp[0], jmp[1]);
/* verify that this is what we expect it to be */
if (((jmp[0] & 0xffff0000) != 0x3d800000) ||
((jmp[1] & 0xffff0000) != 0x398c0000) ||
(jmp[2] != 0x7d8903a6) ||
(jmp[3] != 0x4e800420)) {
pr_err("Not a trampoline\n");
return -EINVAL;
}
tramp = (jmp[1] & 0xffff) |
((jmp[0] & 0xffff) << 16);
if (tramp & 0x8000)
tramp -= 0x10000;
pr_devel(" %lx ", tramp);
if (tramp != addr) {
pr_err("Trampoline location %08lx does not match addr\n",
tramp);
return -EINVAL;
}
op = PPC_INST_NOP;
if (patch_instruction((unsigned int *)ip, op))
return -EPERM;
return 0;
}
#endif /* PPC64 */
#endif /* CONFIG_MODULES */
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
unsigned int old, new;
/*
* 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, 1);
new = PPC_INST_NOP;
return ftrace_modify_code(ip, old, new);
}
#ifdef CONFIG_MODULES
/*
* 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) {
pr_err("No module loaded addr=%lx\n", addr);
return -EFAULT;
}
rec->arch.mod = mod;
} else if (mod) {
if (mod != rec->arch.mod) {
pr_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;
return __ftrace_make_nop(mod, rec, addr);
#else
/* We should not get here without modules */
return -EINVAL;
#endif /* CONFIG_MODULES */
}
#ifdef CONFIG_MODULES
#ifdef CONFIG_PPC64
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int op[2];
void *ip = (void *)rec->ip;
/* read where this goes */
if (probe_kernel_read(op, ip, sizeof(op)))
return -EFAULT;
/*
* We expect to see:
*
* b +8
* ld r2,XX(r1)
*
* The load offset is different depending on the ABI. For simplicity
* just mask it out when doing the compare.
*/
if ((op[0] != 0x48000008) || ((op[1] & 0xffff0000) != 0xe8410000)) {
pr_err("Unexpected call sequence: %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) {
pr_err("No ftrace trampoline\n");
return -EINVAL;
}
/* Ensure branch is within 24 bits */
if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
pr_err("Branch out of range\n");
return -EINVAL;
}
if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
pr_err("REL24 out of range!\n");
return -EINVAL;
}
return 0;
}
#else
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int op;
unsigned long ip = rec->ip;
/* read where this goes */
if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
return -EFAULT;
/* It should be pointing to a nop */
if (op != PPC_INST_NOP) {
pr_err("Expected NOP but have %x\n", op);
return -EINVAL;
}
/* If we never set up a trampoline to ftrace_caller, then bail */
if (!rec->arch.mod->arch.tramp) {
pr_err("No ftrace trampoline\n");
return -EINVAL;
}
/* create the branch to the trampoline */
op = create_branch((unsigned int *)ip,
rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
if (!op) {
pr_err("REL24 out of range!\n");
return -EINVAL;
}
pr_devel("write to %lx\n", rec->ip);
if (patch_instruction((unsigned int *)ip, op))
return -EPERM;
return 0;
}
#endif /* CONFIG_PPC64 */
#endif /* CONFIG_MODULES */
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long ip = rec->ip;
unsigned int old, new;
/*
* 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 = PPC_INST_NOP;
new = ftrace_call_replace(ip, addr, 1);
return ftrace_modify_code(ip, old, new);
}
#ifdef CONFIG_MODULES
/*
* 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) {
pr_err("No module loaded\n");
return -EINVAL;
}
return __ftrace_make_call(rec, addr);
#else
/* We should not get here without modules */
return -EINVAL;
#endif /* CONFIG_MODULES */
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long ip = (unsigned long)(&ftrace_call);
unsigned int old, new;
int ret;
old = *(unsigned int *)&ftrace_call;
new = ftrace_call_replace(ip, (unsigned long)func, 1);
ret = ftrace_modify_code(ip, old, new);
return ret;
}
static int __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
{
unsigned long ftrace_addr = (unsigned long)FTRACE_ADDR;
int ret;
ret = ftrace_update_record(rec, enable);
switch (ret) {
case FTRACE_UPDATE_IGNORE:
return 0;
case FTRACE_UPDATE_MAKE_CALL:
return ftrace_make_call(rec, ftrace_addr);
case FTRACE_UPDATE_MAKE_NOP:
return ftrace_make_nop(NULL, rec, ftrace_addr);
}
return 0;
}
void ftrace_replace_code(int enable)
{
struct ftrace_rec_iter *iter;
struct dyn_ftrace *rec;
int ret;
for (iter = ftrace_rec_iter_start(); iter;
iter = ftrace_rec_iter_next(iter)) {
rec = ftrace_rec_iter_record(iter);
ret = __ftrace_replace_code(rec, enable);
if (ret) {
ftrace_bug(ret, rec->ip);
return;
}
}
}
void arch_ftrace_update_code(int command)
{
if (command & FTRACE_UPDATE_CALLS)
ftrace_replace_code(1);
else if (command & FTRACE_DISABLE_CALLS)
ftrace_replace_code(0);
if (command & FTRACE_UPDATE_TRACE_FUNC)
ftrace_update_ftrace_func(ftrace_trace_function);
if (command & FTRACE_START_FUNC_RET)
ftrace_enable_ftrace_graph_caller();
else if (command & FTRACE_STOP_FUNC_RET)
ftrace_disable_ftrace_graph_caller();
}
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE
extern void ftrace_graph_call(void);
extern void ftrace_graph_stub(void);
int ftrace_enable_ftrace_graph_caller(void)
{
unsigned long ip = (unsigned long)(&ftrace_graph_call);
unsigned long addr = (unsigned long)(&ftrace_graph_caller);
unsigned long stub = (unsigned long)(&ftrace_graph_stub);
unsigned int old, new;
old = ftrace_call_replace(ip, stub, 0);
new = ftrace_call_replace(ip, addr, 0);
return ftrace_modify_code(ip, old, new);
}
int ftrace_disable_ftrace_graph_caller(void)
{
unsigned long ip = (unsigned long)(&ftrace_graph_call);
unsigned long addr = (unsigned long)(&ftrace_graph_caller);
unsigned long stub = (unsigned long)(&ftrace_graph_stub);
unsigned int old, new;
old = ftrace_call_replace(ip, addr, 0);
new = ftrace_call_replace(ip, stub, 0);
return ftrace_modify_code(ip, old, new);
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_PPC64
extern void mod_return_to_handler(void);
#endif
/*
* Hook the return address and push it in the stack of return addrs
* in current thread info.
*/
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
{
unsigned long old;
int faulted;
struct ftrace_graph_ent trace;
unsigned long return_hooker = (unsigned long)&return_to_handler;
if (unlikely(ftrace_graph_is_dead()))
return;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
return;
#ifdef CONFIG_PPC64
/* non core kernel code needs to save and restore the TOC */
if (REGION_ID(self_addr) != KERNEL_REGION_ID)
return_hooker = (unsigned long)&mod_return_to_handler;
#endif
return_hooker = ppc_function_entry((void *)return_hooker);
/*
* Protect against fault, even if it shouldn't
* happen. This tool is too much intrusive to
* ignore such a protection.
*/
asm volatile(
"1: " PPC_LL "%[old], 0(%[parent])\n"
"2: " PPC_STL "%[return_hooker], 0(%[parent])\n"
" li %[faulted], 0\n"
"3:\n"
".section .fixup, \"ax\"\n"
"4: li %[faulted], 1\n"
" b 3b\n"
".previous\n"
".section __ex_table,\"a\"\n"
PPC_LONG_ALIGN "\n"
PPC_LONG "1b,4b\n"
PPC_LONG "2b,4b\n"
".previous"
: [old] "=&r" (old), [faulted] "=r" (faulted)
: [parent] "r" (parent), [return_hooker] "r" (return_hooker)
: "memory"
);
if (unlikely(faulted)) {
ftrace_graph_stop();
WARN_ON(1);
return;
}
trace.func = self_addr;
trace.depth = current->curr_ret_stack + 1;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
*parent = old;
return;
}
if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -EBUSY)
*parent = old;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
#if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64)
unsigned long __init arch_syscall_addr(int nr)
{
return sys_call_table[nr*2];
}
#endif /* CONFIG_FTRACE_SYSCALLS && CONFIG_PPC64 */