linux_dsm_epyc7002/arch/powerpc/kernel/ftrace.c
Thiago Jung Bauermann 7132e2d669 ftrace: Match dot symbols when searching functions on ppc64
In the ppc64 big endian ABI, function symbols point to function
descriptors. The symbols which point to the function entry points
have a dot in front of the function name. Consequently, when the
ftrace filter mechanism searches for the symbol corresponding to
an entry point address, it gets the dot symbol.

As a result, ftrace filter users have to be aware of this ABI detail on
ppc64 and prepend a dot to the function name when setting the filter.

The perf probe command insulates the user from this by ignoring the dot
in front of the symbol name when matching function names to symbols,
but the sysfs interface does not. This patch makes the ftrace filter
mechanism do the same when searching symbols.

Fixes the following failure in ftracetest's kprobe_ftrace.tc:

  .../kprobe_ftrace.tc: line 9: echo: write error: Invalid argument

That failure is on this line of kprobe_ftrace.tc:

  echo _do_fork > set_ftrace_filter

This is because there's no _do_fork entry in the functions list:

  # cat available_filter_functions | grep _do_fork
  ._do_fork

This change introduces no regressions on the perf and ftracetest
testsuite results.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2016-04-27 09:47:29 +10:00

620 lines
14 KiB
C

/*
* 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) {
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;
}
/*
* 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) {
unsigned int inst;
if (probe_kernel_read(&inst, (void *)(ip - 4), 4)) {
pr_err("Fetching instruction at %lx failed.\n", ip - 4);
return -EFAULT;
}
/* We expect either a mlfr r0, or a std r0, LRSAVE(r1) */
if (inst != PPC_INST_MFLR && inst != PPC_INST_STD_LR) {
pr_err("Unexpected instructions around bl _mcount\n"
"when enabling dynamic ftrace!\t"
"(%08x,bl,%08x)\n", inst, op);
return -EINVAL;
}
/* When using -mkernel_profile there is no load to jump over */
pop = PPC_INST_NOP;
}
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 CC_USING_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;
/* 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 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;
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
return ftrace_make_call(rec, addr);
}
#endif
#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 */
}
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);
return;
}
}
}
/*
* 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
#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 */
/*
* 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) == -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 */
#if defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF != 2)
char *arch_ftrace_match_adjust(char *str, const char *search)
{
if (str[0] == '.' && search[0] != '.')
return str + 1;
else
return str;
}
#endif /* defined(CONFIG_PPC64) && (!defined(_CALL_ELF) || _CALL_ELF != 2) */