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linux/arch/powerpc/kernel/trace/ftrace.c

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// SPDX-License-Identifier: GPL-2.0
/*
* 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/asm-prototypes.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:
* We are paranoid about modifying text, as if a bug was to happen, it
* could cause us to read or write to someplace that could cause harm.
* Carefully read and modify the code with probe_kernel_*(), and make
* sure what we read is what we expected it to be before modifying it.
*/
/* 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) {
pr_err("%p: replaced (%#x) != old (%#x)",
(void *)ip, 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 long entry, ptr, tramp;
unsigned long ip = rec->ip;
unsigned int op, pop;
/* read where this goes */
if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {
pr_err("Fetching opcode failed.\n");
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);
pr_devel("ip:%lx jumps to %lx", ip, tramp);
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;
}
#ifdef CONFIG_MPROFILE_KERNEL
/* When using -mkernel_profile there is no load to jump over */
pop = PPC_INST_NOP;
if (probe_kernel_read(&op, (void *)(ip - 4), 4)) {
pr_err("Fetching instruction at %lx failed.\n", ip - 4);
return -EFAULT;
}
/* We expect either a mflr r0, or a std r0, LRSAVE(r1) */
if (op != PPC_INST_MFLR && op != PPC_INST_STD_LR) {
pr_err("Unexpected instruction %08x around bl _mcount\n", op);
return -EINVAL;
}
#else
/*
* 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.
*/
pop = PPC_INST_BRANCH | 8; /* b +8 */
/*
* Check what is in the next instruction. We can see ld r2,40(r1), but
* on first pass after boot we will see mflr r0.
*/
if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE)) {
pr_err("Fetching op failed.\n");
return -EFAULT;
}
if (op != PPC_INST_LD_TOC) {
pr_err("Expected %08x found %08x\n", PPC_INST_LD_TOC, op);
return -EINVAL;
}
#endif /* CONFIG_MPROFILE_KERNEL */
if (patch_instruction((unsigned int *)ip, pop)) {
pr_err("Patching NOP failed.\n");
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
/*
* Examine the existing instructions for __ftrace_make_call.
* They should effectively be a NOP, and follow formal constraints,
* depending on the ABI. Return false if they don't.
*/
#ifndef CONFIG_MPROFILE_KERNEL
static int
expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
{
/*
* 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 ((op0 != 0x48000008) || ((op1 & 0xffff0000) != 0xe8410000))
return 0;
return 1;
}
#else
static int
expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
{
/* look for patched "NOP" on ppc64 with -mprofile-kernel */
if (op0 != PPC_INST_NOP)
return 0;
return 1;
}
#endif
static int
__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned int op[2];
void *ip = (void *)rec->ip;
unsigned long entry, ptr, tramp;
struct module *mod = rec->arch.mod;
/* read where this goes */
if (probe_kernel_read(op, ip, sizeof(op)))
return -EFAULT;
if (!expected_nop_sequence(ip, op[0], op[1])) {
pr_err("Unexpected call sequence at %p: %x %x\n",
ip, op[0], op[1]);
return -EINVAL;
}
/* If we never set up ftrace trampoline(s), then bail */
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
if (!mod->arch.tramp || !mod->arch.tramp_regs) {
#else
if (!mod->arch.tramp) {
#endif
pr_err("No ftrace trampoline\n");
return -EINVAL;
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
if (rec->flags & FTRACE_FL_REGS)
tramp = mod->arch.tramp_regs;
else
#endif
tramp = mod->arch.tramp;
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;
}
/* Ensure branch is within 24 bits */
if (!create_branch(ip, tramp, BRANCH_SET_LINK)) {
pr_err("Branch out of range\n");
return -EINVAL;
}
if (patch_branch(ip, tramp, BRANCH_SET_LINK)) {
pr_err("REL24 out of range!\n");
return -EINVAL;
}
return 0;
}
#else /* !CONFIG_PPC64: */
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 */
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
#ifdef CONFIG_MODULES
static int
__ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
unsigned int op;
unsigned long ip = rec->ip;
unsigned long entry, ptr, tramp;
struct module *mod = rec->arch.mod;
/* If we never set up ftrace trampolines, then bail */
if (!mod->arch.tramp || !mod->arch.tramp_regs) {
pr_err("No ftrace trampoline\n");
return -EINVAL;
}
/* read where this goes */
if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {
pr_err("Fetching opcode failed.\n");
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);
entry = ppc_global_function_entry((void *)old_addr);
pr_devel("ip:%lx jumps to %lx", ip, tramp);
if (tramp != entry) {
/* old_addr is not within range, so we must have used a trampoline */
if (module_trampoline_target(mod, tramp, &ptr)) {
pr_err("Failed to get trampoline target\n");
return -EFAULT;
}
pr_devel("trampoline target %lx", ptr);
/* This should match what was called */
if (ptr != entry) {
pr_err("addr %lx does not match expected %lx\n", ptr, entry);
return -EINVAL;
}
}
/* The new target may be within range */
if (test_24bit_addr(ip, addr)) {
/* within range */
if (patch_branch((unsigned int *)ip, addr, BRANCH_SET_LINK)) {
pr_err("REL24 out of range!\n");
return -EINVAL;
}
return 0;
}
if (rec->flags & FTRACE_FL_REGS)
tramp = mod->arch.tramp_regs;
else
tramp = mod->arch.tramp;
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;
}
/* Ensure branch is within 24 bits */
if (!create_branch((unsigned int *)ip, tramp, BRANCH_SET_LINK)) {
pr_err("Branch out of range\n");
return -EINVAL;
}
if (patch_branch((unsigned int *)ip, tramp, BRANCH_SET_LINK)) {
pr_err("REL24 out of range!\n");
return -EINVAL;
}
return 0;
}
#endif
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
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) && test_24bit_addr(ip, old_addr)) {
/* within range */
old = ftrace_call_replace(ip, old_addr, 1);
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.
*/
if (!rec->arch.mod) {
pr_err("No module loaded\n");
return -EINVAL;
}
return __ftrace_modify_call(rec, old_addr, addr);
#else
/* We should not get here without modules */
return -EINVAL;
#endif /* CONFIG_MODULES */
}
#endif
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);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
/* Also update the regs callback function */
if (!ret) {
ip = (unsigned long)(&ftrace_regs_call);
old = *(unsigned int *)&ftrace_regs_call;
new = ftrace_call_replace(ip, (unsigned long)func, 1);
ret = ftrace_modify_code(ip, old, new);
}
#endif
return ret;
}
/*
* Use the default ftrace_modify_all_code, but without
* stop_machine().
*/
void arch_ftrace_update_code(int command)
{
ftrace_modify_all_code(command);
}
int __init ftrace_dyn_arch_init(void)
{
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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);
}
/*
* Hook the return address and push it in the stack of return addrs
* in current thread info. Return the address we want to divert to.
*/
unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
{
struct ftrace_graph_ent trace;
unsigned long return_hooker;
if (unlikely(ftrace_graph_is_dead()))
goto out;
if (unlikely(atomic_read(&current->tracing_graph_pause)))
goto out;
return_hooker = ppc_function_entry(return_to_handler);
trace.func = ip;
trace.depth = current->curr_ret_stack + 1;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace))
goto out;
if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
NULL) == -EBUSY)
goto out;
parent = return_hooker;
out:
return parent;
}
#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 */
#ifdef PPC64_ELF_ABI_v1
char *arch_ftrace_match_adjust(char *str, const char *search)
{
if (str[0] == '.' && search[0] != '.')
return str + 1;
else
return str;
}
#endif /* PPC64_ELF_ABI_v1 */
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