194 lines
5.2 KiB
C
194 lines
5.2 KiB
C
/*
|
|
* Dynamic function tracer architecture backend.
|
|
*
|
|
* Copyright IBM Corp. 2009
|
|
*
|
|
* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
|
|
* Martin Schwidefsky <schwidefsky@de.ibm.com>
|
|
*/
|
|
|
|
#include <linux/hardirq.h>
|
|
#include <linux/uaccess.h>
|
|
#include <linux/ftrace.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/types.h>
|
|
#include <linux/kprobes.h>
|
|
#include <trace/syscall.h>
|
|
#include <asm/asm-offsets.h>
|
|
#include "entry.h"
|
|
|
|
#ifdef CONFIG_DYNAMIC_FTRACE
|
|
|
|
void ftrace_disable_code(void);
|
|
void ftrace_enable_insn(void);
|
|
|
|
#ifdef CONFIG_64BIT
|
|
/*
|
|
* The 64-bit mcount code looks like this:
|
|
* stg %r14,8(%r15) # offset 0
|
|
* > larl %r1,<&counter> # offset 6
|
|
* > brasl %r14,_mcount # offset 12
|
|
* lg %r14,8(%r15) # offset 18
|
|
* Total length is 24 bytes. The middle two instructions of the mcount
|
|
* block get overwritten by ftrace_make_nop / ftrace_make_call.
|
|
* The 64-bit enabled ftrace code block looks like this:
|
|
* stg %r14,8(%r15) # offset 0
|
|
* > lg %r1,__LC_FTRACE_FUNC # offset 6
|
|
* > lgr %r0,%r0 # offset 12
|
|
* > basr %r14,%r1 # offset 16
|
|
* lg %r14,8(%15) # offset 18
|
|
* The return points of the mcount/ftrace function have the same offset 18.
|
|
* The 64-bit disable ftrace code block looks like this:
|
|
* stg %r14,8(%r15) # offset 0
|
|
* > jg .+18 # offset 6
|
|
* > lgr %r0,%r0 # offset 12
|
|
* > basr %r14,%r1 # offset 16
|
|
* lg %r14,8(%15) # offset 18
|
|
* The jg instruction branches to offset 24 to skip as many instructions
|
|
* as possible.
|
|
*/
|
|
asm(
|
|
" .align 4\n"
|
|
"ftrace_disable_code:\n"
|
|
" jg 0f\n"
|
|
" lgr %r0,%r0\n"
|
|
" basr %r14,%r1\n"
|
|
"0:\n"
|
|
" .align 4\n"
|
|
"ftrace_enable_insn:\n"
|
|
" lg %r1,"__stringify(__LC_FTRACE_FUNC)"\n");
|
|
|
|
#define FTRACE_INSN_SIZE 6
|
|
|
|
#else /* CONFIG_64BIT */
|
|
/*
|
|
* The 31-bit mcount code looks like this:
|
|
* st %r14,4(%r15) # offset 0
|
|
* > bras %r1,0f # offset 4
|
|
* > .long _mcount # offset 8
|
|
* > .long <&counter> # offset 12
|
|
* > 0: l %r14,0(%r1) # offset 16
|
|
* > l %r1,4(%r1) # offset 20
|
|
* basr %r14,%r14 # offset 24
|
|
* l %r14,4(%r15) # offset 26
|
|
* Total length is 30 bytes. The twenty bytes starting from offset 4
|
|
* to offset 24 get overwritten by ftrace_make_nop / ftrace_make_call.
|
|
* The 31-bit enabled ftrace code block looks like this:
|
|
* st %r14,4(%r15) # offset 0
|
|
* > l %r14,__LC_FTRACE_FUNC # offset 4
|
|
* > j 0f # offset 8
|
|
* > .fill 12,1,0x07 # offset 12
|
|
* 0: basr %r14,%r14 # offset 24
|
|
* l %r14,4(%r14) # offset 26
|
|
* The return points of the mcount/ftrace function have the same offset 26.
|
|
* The 31-bit disabled ftrace code block looks like this:
|
|
* st %r14,4(%r15) # offset 0
|
|
* > j .+26 # offset 4
|
|
* > j 0f # offset 8
|
|
* > .fill 12,1,0x07 # offset 12
|
|
* 0: basr %r14,%r14 # offset 24
|
|
* l %r14,4(%r14) # offset 26
|
|
* The j instruction branches to offset 30 to skip as many instructions
|
|
* as possible.
|
|
*/
|
|
asm(
|
|
" .align 4\n"
|
|
"ftrace_disable_code:\n"
|
|
" j 1f\n"
|
|
" j 0f\n"
|
|
" .fill 12,1,0x07\n"
|
|
"0: basr %r14,%r14\n"
|
|
"1:\n"
|
|
" .align 4\n"
|
|
"ftrace_enable_insn:\n"
|
|
" l %r14,"__stringify(__LC_FTRACE_FUNC)"\n");
|
|
|
|
#define FTRACE_INSN_SIZE 4
|
|
|
|
#endif /* CONFIG_64BIT */
|
|
|
|
|
|
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
|
|
unsigned long addr)
|
|
{
|
|
if (probe_kernel_write((void *) rec->ip, ftrace_disable_code,
|
|
MCOUNT_INSN_SIZE))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
|
|
{
|
|
if (probe_kernel_write((void *) rec->ip, ftrace_enable_insn,
|
|
FTRACE_INSN_SIZE))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
int ftrace_update_ftrace_func(ftrace_func_t 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
|
|
/*
|
|
* Hook the return address and push it in the stack of return addresses
|
|
* in current thread info.
|
|
*/
|
|
unsigned long __kprobes prepare_ftrace_return(unsigned long parent,
|
|
unsigned long ip)
|
|
{
|
|
struct ftrace_graph_ent trace;
|
|
|
|
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
|
|
goto out;
|
|
ip = (ip & PSW_ADDR_INSN) - MCOUNT_INSN_SIZE;
|
|
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 = (unsigned long) return_to_handler;
|
|
out:
|
|
return parent;
|
|
}
|
|
|
|
#ifdef CONFIG_DYNAMIC_FTRACE
|
|
/*
|
|
* Patch the kernel code at ftrace_graph_caller location. The instruction
|
|
* there is branch relative and save to prepare_ftrace_return. To disable
|
|
* the call to prepare_ftrace_return we patch the bras offset to point
|
|
* directly after the instructions. To enable the call we calculate
|
|
* the original offset to prepare_ftrace_return and put it back.
|
|
*/
|
|
int ftrace_enable_ftrace_graph_caller(void)
|
|
{
|
|
unsigned short offset;
|
|
|
|
offset = ((void *) prepare_ftrace_return -
|
|
(void *) ftrace_graph_caller) / 2;
|
|
return probe_kernel_write((void *) ftrace_graph_caller + 2,
|
|
&offset, sizeof(offset));
|
|
}
|
|
|
|
int ftrace_disable_ftrace_graph_caller(void)
|
|
{
|
|
static unsigned short offset = 0x0002;
|
|
|
|
return probe_kernel_write((void *) ftrace_graph_caller + 2,
|
|
&offset, sizeof(offset));
|
|
}
|
|
|
|
#endif /* CONFIG_DYNAMIC_FTRACE */
|
|
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|