240 lines
6.4 KiB
C
240 lines
6.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* Dynamic function tracer architecture backend.
|
|
*
|
|
* Copyright IBM Corp. 2009,2014
|
|
*
|
|
* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
|
|
* Martin Schwidefsky <schwidefsky@de.ibm.com>
|
|
*/
|
|
|
|
#include <linux/moduleloader.h>
|
|
#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 <asm/cacheflush.h>
|
|
#include <asm/set_memory.h>
|
|
#include "entry.h"
|
|
|
|
/*
|
|
* The 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. Only the first instruction will be patched
|
|
* by ftrace_make_call / ftrace_make_nop.
|
|
* The enabled ftrace code block looks like this:
|
|
* > brasl %r0,ftrace_caller # offset 0
|
|
* larl %r1,<&counter> # offset 6
|
|
* brasl %r14,_mcount # offset 12
|
|
* lg %r14,8(%r15) # offset 18
|
|
* The ftrace function gets called with a non-standard C function call ABI
|
|
* where r0 contains the return address. It is also expected that the called
|
|
* function only clobbers r0 and r1, but restores r2-r15.
|
|
* For module code we can't directly jump to ftrace caller, but need a
|
|
* trampoline (ftrace_plt), which clobbers also r1.
|
|
* The return point of the ftrace function has offset 24, so execution
|
|
* continues behind the mcount block.
|
|
* The disabled ftrace code block looks like this:
|
|
* > jg .+24 # offset 0
|
|
* larl %r1,<&counter> # offset 6
|
|
* brasl %r14,_mcount # offset 12
|
|
* lg %r14,8(%r15) # offset 18
|
|
* The jg instruction branches to offset 24 to skip as many instructions
|
|
* as possible.
|
|
* In case we use gcc's hotpatch feature the original and also the disabled
|
|
* function prologue contains only a single six byte instruction and looks
|
|
* like this:
|
|
* > brcl 0,0 # offset 0
|
|
* To enable ftrace the code gets patched like above and afterwards looks
|
|
* like this:
|
|
* > brasl %r0,ftrace_caller # offset 0
|
|
*/
|
|
|
|
unsigned long ftrace_plt;
|
|
|
|
static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn)
|
|
{
|
|
#if defined(CC_USING_HOTPATCH) || defined(CC_USING_NOP_MCOUNT)
|
|
/* brcl 0,0 */
|
|
insn->opc = 0xc004;
|
|
insn->disp = 0;
|
|
#else
|
|
/* stg r14,8(r15) */
|
|
insn->opc = 0xe3e0;
|
|
insn->disp = 0xf0080024;
|
|
#endif
|
|
}
|
|
|
|
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
|
|
unsigned long addr)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
|
|
unsigned long addr)
|
|
{
|
|
struct ftrace_insn orig, new, old;
|
|
|
|
if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
|
|
return -EFAULT;
|
|
if (addr == MCOUNT_ADDR) {
|
|
/* Initial code replacement */
|
|
ftrace_generate_orig_insn(&orig);
|
|
ftrace_generate_nop_insn(&new);
|
|
} else {
|
|
/* Replace ftrace call with a nop. */
|
|
ftrace_generate_call_insn(&orig, rec->ip);
|
|
ftrace_generate_nop_insn(&new);
|
|
}
|
|
/* Verify that the to be replaced code matches what we expect. */
|
|
if (memcmp(&orig, &old, sizeof(old)))
|
|
return -EINVAL;
|
|
s390_kernel_write((void *) rec->ip, &new, sizeof(new));
|
|
return 0;
|
|
}
|
|
|
|
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
|
|
{
|
|
struct ftrace_insn orig, new, old;
|
|
|
|
if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
|
|
return -EFAULT;
|
|
/* Replace nop with an ftrace call. */
|
|
ftrace_generate_nop_insn(&orig);
|
|
ftrace_generate_call_insn(&new, rec->ip);
|
|
|
|
/* Verify that the to be replaced code matches what we expect. */
|
|
if (memcmp(&orig, &old, sizeof(old)))
|
|
return -EINVAL;
|
|
s390_kernel_write((void *) rec->ip, &new, sizeof(new));
|
|
return 0;
|
|
}
|
|
|
|
int ftrace_update_ftrace_func(ftrace_func_t func)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
int __init ftrace_dyn_arch_init(void)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_MODULES
|
|
|
|
static int __init ftrace_plt_init(void)
|
|
{
|
|
unsigned int *ip;
|
|
|
|
ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE);
|
|
if (!ftrace_plt)
|
|
panic("cannot allocate ftrace plt\n");
|
|
ip = (unsigned int *) ftrace_plt;
|
|
ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
|
|
ip[1] = 0x100a0004;
|
|
ip[2] = 0x07f10000;
|
|
ip[3] = FTRACE_ADDR >> 32;
|
|
ip[4] = FTRACE_ADDR & 0xffffffff;
|
|
set_memory_ro(ftrace_plt, 1);
|
|
return 0;
|
|
}
|
|
device_initcall(ftrace_plt_init);
|
|
|
|
#endif /* CONFIG_MODULES */
|
|
|
|
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
|
|
/*
|
|
* Hook the return address and push it in the stack of return addresses
|
|
* in current thread info.
|
|
*/
|
|
unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
|
|
unsigned long ip)
|
|
{
|
|
if (unlikely(ftrace_graph_is_dead()))
|
|
goto out;
|
|
if (unlikely(atomic_read(¤t->tracing_graph_pause)))
|
|
goto out;
|
|
ip -= MCOUNT_INSN_SIZE;
|
|
if (!function_graph_enter(ra, ip, 0, (void *) sp))
|
|
ra = (unsigned long) return_to_handler;
|
|
out:
|
|
return ra;
|
|
}
|
|
NOKPROBE_SYMBOL(prepare_ftrace_return);
|
|
|
|
/*
|
|
* Patch the kernel code at ftrace_graph_caller location. The instruction
|
|
* there is branch relative on condition. To enable the ftrace graph code
|
|
* block, we simply patch the mask field of the instruction to zero and
|
|
* turn the instruction into a nop.
|
|
* To disable the ftrace graph code the mask field will be patched to
|
|
* all ones, which turns the instruction into an unconditional branch.
|
|
*/
|
|
int ftrace_enable_ftrace_graph_caller(void)
|
|
{
|
|
u8 op = 0x04; /* set mask field to zero */
|
|
|
|
s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
|
|
return 0;
|
|
}
|
|
|
|
int ftrace_disable_ftrace_graph_caller(void)
|
|
{
|
|
u8 op = 0xf4; /* set mask field to all ones */
|
|
|
|
s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
|
|
return 0;
|
|
}
|
|
|
|
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
|
|
|
|
#ifdef CONFIG_KPROBES_ON_FTRACE
|
|
void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
|
|
struct ftrace_ops *ops, struct pt_regs *regs)
|
|
{
|
|
struct kprobe_ctlblk *kcb;
|
|
struct kprobe *p = get_kprobe((kprobe_opcode_t *)ip);
|
|
|
|
if (unlikely(!p) || kprobe_disabled(p))
|
|
return;
|
|
|
|
if (kprobe_running()) {
|
|
kprobes_inc_nmissed_count(p);
|
|
return;
|
|
}
|
|
|
|
__this_cpu_write(current_kprobe, p);
|
|
|
|
kcb = get_kprobe_ctlblk();
|
|
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
|
|
|
|
instruction_pointer_set(regs, ip);
|
|
|
|
if (!p->pre_handler || !p->pre_handler(p, regs)) {
|
|
|
|
instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
|
|
|
|
if (unlikely(p->post_handler)) {
|
|
kcb->kprobe_status = KPROBE_HIT_SSDONE;
|
|
p->post_handler(p, regs, 0);
|
|
}
|
|
}
|
|
__this_cpu_write(current_kprobe, NULL);
|
|
}
|
|
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
|
|
|
|
int arch_prepare_kprobe_ftrace(struct kprobe *p)
|
|
{
|
|
p->ainsn.insn = NULL;
|
|
return 0;
|
|
}
|
|
#endif
|