arch/s390/kernel/ftrace.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Dynamic function tracer architecture backend.
   4  *
   5  * Copyright IBM Corp. 2009,2014
   6  *
   7  *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
   8  *              Martin Schwidefsky <schwidefsky@de.ibm.com>
   9  */
  10
  11 #include <linux/moduleloader.h>
  12 #include <linux/hardirq.h>
  13 #include <linux/uaccess.h>
  14 #include <linux/ftrace.h>
  15 #include <linux/kernel.h>
  16 #include <linux/types.h>
  17 #include <linux/kprobes.h>
  18 #include <trace/syscall.h>
  19 #include <asm/asm-offsets.h>
  20 #include <asm/cacheflush.h>
  21 #include <asm/set_memory.h>
  22 #include "entry.h"
  23
  24 /*
  25  * To generate function prologue either gcc's hotpatch feature (since gcc 4.8)
  26  * or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags
  27  * (since gcc 9 / clang 10) is used.
  28  * In both cases the original and also the disabled function prologue contains
  29  * only a single six byte instruction and looks like this:
  30  * >    brcl    0,0                     # offset 0
  31  * To enable ftrace the code gets patched like above and afterwards looks
  32  * like this:
  33  * >    brasl   %r0,ftrace_caller       # offset 0
  34  *
  35  * The instruction will be patched by ftrace_make_call / ftrace_make_nop.
  36  * The ftrace function gets called with a non-standard C function call ABI
  37  * where r0 contains the return address. It is also expected that the called
  38  * function only clobbers r0 and r1, but restores r2-r15.
  39  * For module code we can't directly jump to ftrace caller, but need a
  40  * trampoline (ftrace_plt), which clobbers also r1.
  41  */
  42
  43 unsigned long ftrace_plt;
  44
  45 int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
  46                        unsigned long addr)
  47 {
  48         return 0;
  49 }
  50
  51 int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
  52                     unsigned long addr)
  53 {
  54         struct ftrace_insn orig, new, old;
  55
  56         if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
  57                 return -EFAULT;
  58         /* Replace ftrace call with a nop. */
  59         ftrace_generate_call_insn(&orig, rec->ip);
  60         ftrace_generate_nop_insn(&new);
  61
  62         /* Verify that the to be replaced code matches what we expect. */
  63         if (memcmp(&orig, &old, sizeof(old)))
  64                 return -EINVAL;
  65         s390_kernel_write((void *) rec->ip, &new, sizeof(new));
  66         return 0;
  67 }
  68
  69 int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
  70 {
  71         struct ftrace_insn orig, new, old;
  72
  73         if (copy_from_kernel_nofault(&old, (void *) rec->ip, sizeof(old)))
  74                 return -EFAULT;
  75         /* Replace nop with an ftrace call. */
  76         ftrace_generate_nop_insn(&orig);
  77         ftrace_generate_call_insn(&new, rec->ip);
  78
  79         /* Verify that the to be replaced code matches what we expect. */
  80         if (memcmp(&orig, &old, sizeof(old)))
  81                 return -EINVAL;
  82         s390_kernel_write((void *) rec->ip, &new, sizeof(new));
  83         return 0;
  84 }
  85
  86 int ftrace_update_ftrace_func(ftrace_func_t func)
  87 {
  88         return 0;
  89 }
  90
  91 int __init ftrace_dyn_arch_init(void)
  92 {
  93         return 0;
  94 }
  95
  96 #ifdef CONFIG_MODULES
  97
  98 static int __init ftrace_plt_init(void)
  99 {
 100         unsigned int *ip;
 101
 102         ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE);
 103         if (!ftrace_plt)
 104                 panic("cannot allocate ftrace plt\n");
 105         ip = (unsigned int *) ftrace_plt;
 106         ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
 107         ip[1] = 0x100a0004;
 108         ip[2] = 0x07f10000;
 109         ip[3] = FTRACE_ADDR >> 32;
 110         ip[4] = FTRACE_ADDR & 0xffffffff;
 111         set_memory_ro(ftrace_plt, 1);
 112         return 0;
 113 }
 114 device_initcall(ftrace_plt_init);
 115
 116 #endif /* CONFIG_MODULES */
 117
 118 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 119 /*
 120  * Hook the return address and push it in the stack of return addresses
 121  * in current thread info.
 122  */
 123 unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
 124                                     unsigned long ip)
 125 {
 126         if (unlikely(ftrace_graph_is_dead()))
 127                 goto out;
 128         if (unlikely(atomic_read(&current->tracing_graph_pause)))
 129                 goto out;
 130         ip -= MCOUNT_INSN_SIZE;
 131         if (!function_graph_enter(ra, ip, 0, (void *) sp))
 132                 ra = (unsigned long) return_to_handler;
 133 out:
 134         return ra;
 135 }
 136 NOKPROBE_SYMBOL(prepare_ftrace_return);
 137
 138 /*
 139  * Patch the kernel code at ftrace_graph_caller location. The instruction
 140  * there is branch relative on condition. To enable the ftrace graph code
 141  * block, we simply patch the mask field of the instruction to zero and
 142  * turn the instruction into a nop.
 143  * To disable the ftrace graph code the mask field will be patched to
 144  * all ones, which turns the instruction into an unconditional branch.
 145  */
 146 int ftrace_enable_ftrace_graph_caller(void)
 147 {
 148         u8 op = 0x04; /* set mask field to zero */
 149
 150         s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
 151         return 0;
 152 }
 153
 154 int ftrace_disable_ftrace_graph_caller(void)
 155 {
 156         u8 op = 0xf4; /* set mask field to all ones */
 157
 158         s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
 159         return 0;
 160 }
 161
 162 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 163
 164 #ifdef CONFIG_KPROBES_ON_FTRACE
 165 void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 166                 struct ftrace_ops *ops, struct ftrace_regs *fregs)
 167 {
 168         struct kprobe_ctlblk *kcb;
 169         struct pt_regs *regs;
 170         struct kprobe *p;
 171         int bit;
 172
 173         bit = ftrace_test_recursion_trylock(ip, parent_ip);
 174         if (bit < 0)
 175                 return;
 176
 177         regs = ftrace_get_regs(fregs);
 178         preempt_disable_notrace();
 179         p = get_kprobe((kprobe_opcode_t *)ip);
 180         if (unlikely(!p) || kprobe_disabled(p))
 181                 goto out;
 182
 183         if (kprobe_running()) {
 184                 kprobes_inc_nmissed_count(p);
 185                 goto out;
 186         }
 187
 188         __this_cpu_write(current_kprobe, p);
 189
 190         kcb = get_kprobe_ctlblk();
 191         kcb->kprobe_status = KPROBE_HIT_ACTIVE;
 192
 193         instruction_pointer_set(regs, ip);
 194
 195         if (!p->pre_handler || !p->pre_handler(p, regs)) {
 196
 197                 instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
 198
 199                 if (unlikely(p->post_handler)) {
 200                         kcb->kprobe_status = KPROBE_HIT_SSDONE;
 201                         p->post_handler(p, regs, 0);
 202                 }
 203         }
 204         __this_cpu_write(current_kprobe, NULL);
 205 out:
 206         preempt_enable_notrace();
 207         ftrace_test_recursion_unlock(bit);
 208 }
 209 NOKPROBE_SYMBOL(kprobe_ftrace_handler);
 210
 211 int arch_prepare_kprobe_ftrace(struct kprobe *p)
 212 {
 213         p->ainsn.insn = NULL;
 214         return 0;
 215 }
 216 #endif