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linux_dsm_epyc7002/arch/powerpc/kernel/ftrace.c
Steven Rostedt bb7253403f powerpc64, ftrace: save toc only on modules for function graph 
The TOCS used by modules are different than the one used by
the core kernel code. The function graph tracer must save and
restore the TOC whenever it traces a module call. But this
is an added overhead to burden the majority of core kernel
code being traced.

Benjamin Herrenschmidt suggested in testing the entry of
the call to tell if it is a core kernel function or a module.
He recommended using the REGION_ID() macro to perform this test.

This patch implements Benjamin's idea, and uses a different
return_to_handler routine dependent on if the entry is a core
kernel function or not. The module version saves the TOC, where as
the core kernel version does not.

Geoff Lavand tested on PS3.

Tested-by: Geoff Levand <geoffrey.levand@am.sony.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2009-02-23 10:48:54 +11:00

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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>
#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
#ifdef CONFIG_DYNAMIC_FTRACE
static unsigned int ftrace_nop = PPC_NOP_INSTR;
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, int link)
{
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);
/* if (link) set op to 'bl' else 'b' */
op = 0x48000000 | (link ? 1 : 0);
op |= (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)
{
/* 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_debug("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_debug(" %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_debug(" %x ", offset);
/* get the address this jumps too */
tramp = mod->arch.toc + offset + 32;
pr_debug("toc: %lx", tramp);
if (probe_kernel_read(jmp, (void *)tramp, 8)) {
printk(KERN_ERR "Failed to read %lx\n", tramp);
return -EFAULT;
}
pr_debug(" %08x %08x\n", jmp[0], jmp[1]);
ptr = ((unsigned long)jmp[0] << 32) + jmp[1];
/* 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(&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_debug("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_debug(" %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_debug(" %x ", tramp);
if (tramp != addr) {
printk(KERN_ERR
"Trampoline location %08lx does not match addr\n",
tramp);
return -EINVAL;
}
op = PPC_NOP_INSTR;
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 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, 1);
new = ftrace_nop_replace();
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_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;
}
/* 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_debug("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_NOP_INSTR) {
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_debug("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 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, 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 char old[MCOUNT_INSN_SIZE], *new;
int ret;
memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
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 char old[MCOUNT_INSN_SIZE], *new;
new = ftrace_call_replace(ip, stub, 0);
memcpy(old, new, MCOUNT_INSN_SIZE);
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 char old[MCOUNT_INSN_SIZE], *new;
new = ftrace_call_replace(ip, addr, 0);
memcpy(old, new, MCOUNT_INSN_SIZE);
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;
unsigned long long calltime;
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;
#if 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 = GET_ADDR(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:"
".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;
}
calltime = cpu_clock(raw_smp_processor_id());
if (ftrace_push_return_trace(old, calltime,
self_addr, &trace.depth) == -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 */
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