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/*
* Dynamic function tracer architecture backend.
*
* Copyright IBM Corp. 2009
*
* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
*
*/
#include <linux/hardirq.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <asm/lowcore.h>
#ifdef CONFIG_DYNAMIC_FTRACE
void ftrace_disable_code(void);
void ftrace_disable_return(void);
void ftrace_call_code(void);
void ftrace_nop_code(void);
#define FTRACE_INSN_SIZE 4
#ifdef CONFIG_64BIT
asm(
" .align 4\n"
"ftrace_disable_code:\n"
" j 0f\n"
" .word 0x0024\n"
" lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n"
" basr %r14,%r1\n"
"ftrace_disable_return:\n"
" lg %r14,8(15)\n"
" lgr %r0,%r0\n"
"0:\n");
asm(
" .align 4\n"
"ftrace_nop_code:\n"
" j .+"__stringify(MCOUNT_INSN_SIZE)"\n");
asm(
" .align 4\n"
"ftrace_call_code:\n"
" stg %r14,8(%r15)\n");
#else /* CONFIG_64BIT */
asm(
" .align 4\n"
"ftrace_disable_code:\n"
" j 0f\n"
" l %r1,"__stringify(__LC_FTRACE_FUNC)"\n"
" basr %r14,%r1\n"
"ftrace_disable_return:\n"
" l %r14,4(%r15)\n"
" j 0f\n"
" bcr 0,%r7\n"
" bcr 0,%r7\n"
" bcr 0,%r7\n"
" bcr 0,%r7\n"
" bcr 0,%r7\n"
" bcr 0,%r7\n"
"0:\n");
asm(
" .align 4\n"
"ftrace_nop_code:\n"
" j .+"__stringify(MCOUNT_INSN_SIZE)"\n");
asm(
" .align 4\n"
"ftrace_call_code:\n"
" st %r14,4(%r15)\n");
#endif /* CONFIG_64BIT */
static int ftrace_modify_code(unsigned long ip,
void *old_code, int old_size,
void *new_code, int new_size)
{
unsigned char replaced[MCOUNT_INSN_SIZE];
/*
* Note: Due to modules 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.
* This however is just a simple sanity check.
*/
if (probe_kernel_read(replaced, (void *)ip, old_size))
return -EFAULT;
if (memcmp(replaced, old_code, old_size) != 0)
return -EINVAL;
if (probe_kernel_write((void *)ip, new_code, new_size))
return -EPERM;
return 0;
}
static int ftrace_make_initial_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
return ftrace_modify_code(rec->ip,
ftrace_call_code, FTRACE_INSN_SIZE,
ftrace_disable_code, MCOUNT_INSN_SIZE);
}
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
if (addr == MCOUNT_ADDR)
return ftrace_make_initial_nop(mod, rec, addr);
return ftrace_modify_code(rec->ip,
ftrace_call_code, FTRACE_INSN_SIZE,
ftrace_nop_code, FTRACE_INSN_SIZE);
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
return ftrace_modify_code(rec->ip,
ftrace_nop_code, FTRACE_INSN_SIZE,
ftrace_call_code, FTRACE_INSN_SIZE);
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
ftrace_dyn_func = (unsigned long)func;
return 0;
}
int __init ftrace_dyn_arch_init(void *data)
{
*(unsigned long *)data = 0;
return 0;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
#ifdef CONFIG_DYNAMIC_FTRACE
/*
* Patch the kernel code at ftrace_graph_caller location:
* The instruction there is branch relative on condition. The condition mask
* is either all ones (always branch aka disable ftrace_graph_caller) or all
* zeroes (nop aka enable ftrace_graph_caller).
* Instruction format for brc is a7m4xxxx where m is the condition mask.
*/
int ftrace_enable_ftrace_graph_caller(void)
{
unsigned short opcode = 0xa704;
return probe_kernel_write(ftrace_graph_caller, &opcode, sizeof(opcode));
}
int ftrace_disable_ftrace_graph_caller(void)
{
unsigned short opcode = 0xa7f4;
return probe_kernel_write(ftrace_graph_caller, &opcode, sizeof(opcode));
}
static inline unsigned long ftrace_mcount_call_adjust(unsigned long addr)
{
return addr - (ftrace_disable_return - ftrace_disable_code);
}
#else /* CONFIG_DYNAMIC_FTRACE */
static inline unsigned long ftrace_mcount_call_adjust(unsigned long addr)
{
return addr - MCOUNT_OFFSET_RET;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
/*
* Hook the return address and push it in the stack of return addresses
* in current thread info.
*/
unsigned long prepare_ftrace_return(unsigned long ip, unsigned long parent)
{
struct ftrace_graph_ent trace;
/* Nmi's are currently unsupported. */
if (unlikely(in_nmi()))
goto out;
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
goto out;
if (ftrace_push_return_trace(parent, ip, &trace.depth) == -EBUSY)
goto out;
trace.func = ftrace_mcount_call_adjust(ip) & PSW_ADDR_INSN;
/* Only trace if the calling function expects to. */
if (!ftrace_graph_entry(&trace)) {
current->curr_ret_stack--;
goto out;
}
parent = (unsigned long)return_to_handler;
out:
return parent;
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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