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linux/arch/powerpc/kernel/ftrace.c
Ian Munsie 02424d8966 powerpc/ftrace: Implement raw syscall tracepoints on PowerPC 
This patch implements the raw syscall tracepoints on PowerPC and exports
them for ftrace syscalls to use.

To minimise reworking existing code, I slightly re-ordered the thread
info flags such that the new TIF_SYSCALL_TRACEPOINT bit would still fit
within the 16 bits of the andi. instruction's UI field. The instructions
in question are in /arch/powerpc/kernel/entry_{32,64}.S to and the
_TIF_SYSCALL_T_OR_A with the thread flags to see if system call tracing
is enabled.

In the case of 64bit PowerPC, arch_syscall_addr and
arch_syscall_match_sym_name are overridden to allow ftrace syscalls to
work given the unusual system call table structure and symbol names that
start with a period.

Signed-off-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2011-05-26 13:38:57 +10:00

611 lines
14 KiB
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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.
*
* Added function graph tracer code, taken from x86 that was written
* by Frederic Weisbecker, and ported to PPC by Steven Rostedt.
*
*/
#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 (probe_kernel_write((void *)ip, &new, 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)
{
/* 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 int jmp[5];
unsigned long ptr;
unsigned long ip = rec->ip;
unsigned long tramp;
int offset;
/* 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)) {
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)
*/
pr_devel("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, sizeof(jmp))) {
printk(KERN_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) != 0x3d820000) ||
((jmp[1] & 0xffff0000) != 0x398c0000) ||
(jmp[2] != 0xf8410028) ||
(jmp[3] != 0xe96c0020) ||
(jmp[4] != 0xe84c0028)) {
printk(KERN_ERR "Not a trampoline\n");
return -EINVAL;
}
/* The bottom half is signed extended */
offset = ((unsigned)((unsigned short)jmp[0]) << 16) +
(int)((short)jmp[1]);
pr_devel(" %x ", offset);
/* get the address this jumps too */
tramp = mod->arch.toc + offset + 32;
pr_devel("toc: %lx", tramp);
if (probe_kernel_read(jmp, (void *)tramp, 8)) {
printk(KERN_ERR "Failed to read %lx\n", tramp);
return -EFAULT;
}
pr_devel(" %08x %08x\n", jmp[0], jmp[1]);
ptr = ((unsigned long)jmp[0] << 32) + jmp[1];
/* This should match what was called */
if (ptr != ppc_function_entry((void *)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(&op, (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 = 0x48000008; /* b +8 */
if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
return -EPERM;
flush_icache_range(ip, ip + 8);
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)) {
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 PPC32 the trampoline looks like:
* 0x3d, 0x60, 0x00, 0x00 lis r11,sym@ha
* 0x39, 0x6b, 0x00, 0x00 addi r11,r11,sym@l
* 0x7d, 0x69, 0x03, 0xa6 mtctr r11
* 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))) {
printk(KERN_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) != 0x3d600000) ||
((jmp[1] & 0xffff0000) != 0x396b0000) ||
(jmp[2] != 0x7d6903a6) ||
(jmp[3] != 0x4e800420)) {
printk(KERN_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) {
printk(KERN_ERR
"Trampoline location %08lx does not match addr\n",
tramp);
return -EINVAL;
}
op = PPC_INST_NOP;
if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
return -EPERM;
flush_icache_range(ip, ip + 8);
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) {
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;
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];
unsigned long ip = rec->ip;
/* read where this goes */
if (probe_kernel_read(op, (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_INST_NOP) || (op[1] != PPC_INST_NOP))) {
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;
}
/* create the branch to the trampoline */
op[0] = create_branch((unsigned int *)ip,
rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
if (!op[0]) {
printk(KERN_ERR "REL24 out of range!\n");
return -EINVAL;
}
/* ld r2,40(r1) */
op[1] = 0xe8410028;
pr_devel("write to %lx\n", rec->ip);
if (probe_kernel_write((void *)ip, op, MCOUNT_INSN_SIZE * 2))
return -EPERM;
flush_icache_range(ip, ip + 8);
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) {
printk(KERN_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) {
printk(KERN_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) {
printk(KERN_ERR "REL24 out of range!\n");
return -EINVAL;
}
pr_devel("write to %lx\n", rec->ip);
if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
return -EPERM;
flush_icache_range(ip, ip + 8);
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) {
printk(KERN_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;
}
int __init ftrace_dyn_arch_init(void *data)
{
/* caller expects data to be zero */
unsigned long *p = data;
*p = 0;
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(atomic_read(&current->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;
}
if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -EBUSY) {
*parent = old;
return;
}
trace.func = self_addr;
/* Only trace if the calling function expects to */
if (!ftrace_graph_entry(&trace)) {
current->curr_ret_stack--;
*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 */
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