| // 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" |
| |
| /* |
| * To generate function prologue either gcc's hotpatch feature (since gcc 4.8) |
| * or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags |
| * (since gcc 9 / clang 10) is used. |
| * In both cases 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 |
| * |
| * The instruction will be patched by ftrace_make_call / ftrace_make_nop. |
| * 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. |
| */ |
| |
| void *ftrace_func __read_mostly = ftrace_stub; |
| unsigned long ftrace_plt; |
| |
| 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; |
| /* 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) |
| { |
| ftrace_func = 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 ftrace_regs *fregs) |
| { |
| struct kprobe_ctlblk *kcb; |
| struct pt_regs *regs; |
| struct kprobe *p; |
| int bit; |
| |
| bit = ftrace_test_recursion_trylock(ip, parent_ip); |
| if (bit < 0) |
| return; |
| |
| regs = ftrace_get_regs(fregs); |
| preempt_disable_notrace(); |
| p = get_kprobe((kprobe_opcode_t *)ip); |
| if (unlikely(!p) || kprobe_disabled(p)) |
| goto out; |
| |
| if (kprobe_running()) { |
| kprobes_inc_nmissed_count(p); |
| goto out; |
| } |
| |
| __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); |
| out: |
| preempt_enable_notrace(); |
| ftrace_test_recursion_unlock(bit); |
| } |
| NOKPROBE_SYMBOL(kprobe_ftrace_handler); |
| |
| int arch_prepare_kprobe_ftrace(struct kprobe *p) |
| { |
| p->ainsn.insn = NULL; |
| return 0; |
| } |
| #endif |