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![Li kunyu](/assets/img/avatar_default.png)
All instances of the function ftrace_arch_modify_prepare() and ftrace_arch_modify_post_process() return zero. There's no point in checking their return value. Just have them be void functions. Link: https://lkml.kernel.org/r/20220518023639.4065-1-kunyu@nfschina.com Signed-off-by: Li kunyu <kunyu@nfschina.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
360 lines
9.2 KiB
C
360 lines
9.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Dynamic function tracer architecture backend.
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*
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* Copyright IBM Corp. 2009,2014
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*
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* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
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*/
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#include <linux/moduleloader.h>
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#include <linux/hardirq.h>
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#include <linux/uaccess.h>
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#include <linux/ftrace.h>
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include <linux/kprobes.h>
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#include <trace/syscall.h>
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#include <asm/asm-offsets.h>
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#include <asm/text-patching.h>
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#include <asm/cacheflush.h>
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#include <asm/ftrace.lds.h>
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#include <asm/nospec-branch.h>
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#include <asm/set_memory.h>
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#include "entry.h"
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#include "ftrace.h"
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/*
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* To generate function prologue either gcc's hotpatch feature (since gcc 4.8)
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* or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags
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* (since gcc 9 / clang 10) is used.
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* In both cases the original and also the disabled function prologue contains
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* only a single six byte instruction and looks like this:
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* > brcl 0,0 # offset 0
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* To enable ftrace the code gets patched like above and afterwards looks
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* like this:
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* > brasl %r0,ftrace_caller # offset 0
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*
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* The instruction will be patched by ftrace_make_call / ftrace_make_nop.
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* The ftrace function gets called with a non-standard C function call ABI
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* where r0 contains the return address. It is also expected that the called
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* function only clobbers r0 and r1, but restores r2-r15.
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* For module code we can't directly jump to ftrace caller, but need a
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* trampoline (ftrace_plt), which clobbers also r1.
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*/
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void *ftrace_func __read_mostly = ftrace_stub;
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struct ftrace_insn {
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u16 opc;
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s32 disp;
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} __packed;
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asm(
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" .align 16\n"
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"ftrace_shared_hotpatch_trampoline_br:\n"
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" lmg %r0,%r1,2(%r1)\n"
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" br %r1\n"
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"ftrace_shared_hotpatch_trampoline_br_end:\n"
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);
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#ifdef CONFIG_EXPOLINE
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asm(
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" .align 16\n"
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"ftrace_shared_hotpatch_trampoline_exrl:\n"
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" lmg %r0,%r1,2(%r1)\n"
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" exrl %r0,0f\n"
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" j .\n"
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"0: br %r1\n"
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"ftrace_shared_hotpatch_trampoline_exrl_end:\n"
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);
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#endif /* CONFIG_EXPOLINE */
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#ifdef CONFIG_MODULES
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static char *ftrace_plt;
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#endif /* CONFIG_MODULES */
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static const char *ftrace_shared_hotpatch_trampoline(const char **end)
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{
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const char *tstart, *tend;
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tstart = ftrace_shared_hotpatch_trampoline_br;
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tend = ftrace_shared_hotpatch_trampoline_br_end;
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#ifdef CONFIG_EXPOLINE
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if (!nospec_disable) {
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tstart = ftrace_shared_hotpatch_trampoline_exrl;
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tend = ftrace_shared_hotpatch_trampoline_exrl_end;
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}
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#endif /* CONFIG_EXPOLINE */
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if (end)
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*end = tend;
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return tstart;
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}
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bool ftrace_need_init_nop(void)
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{
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return true;
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}
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int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
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{
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static struct ftrace_hotpatch_trampoline *next_vmlinux_trampoline =
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__ftrace_hotpatch_trampolines_start;
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static const char orig[6] = { 0xc0, 0x04, 0x00, 0x00, 0x00, 0x00 };
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static struct ftrace_hotpatch_trampoline *trampoline;
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struct ftrace_hotpatch_trampoline **next_trampoline;
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struct ftrace_hotpatch_trampoline *trampolines_end;
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struct ftrace_hotpatch_trampoline tmp;
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struct ftrace_insn *insn;
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const char *shared;
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s32 disp;
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BUILD_BUG_ON(sizeof(struct ftrace_hotpatch_trampoline) !=
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SIZEOF_FTRACE_HOTPATCH_TRAMPOLINE);
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next_trampoline = &next_vmlinux_trampoline;
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trampolines_end = __ftrace_hotpatch_trampolines_end;
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shared = ftrace_shared_hotpatch_trampoline(NULL);
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#ifdef CONFIG_MODULES
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if (mod) {
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next_trampoline = &mod->arch.next_trampoline;
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trampolines_end = mod->arch.trampolines_end;
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shared = ftrace_plt;
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}
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#endif
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if (WARN_ON_ONCE(*next_trampoline >= trampolines_end))
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return -ENOMEM;
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trampoline = (*next_trampoline)++;
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/* Check for the compiler-generated fentry nop (brcl 0, .). */
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if (WARN_ON_ONCE(memcmp((const void *)rec->ip, &orig, sizeof(orig))))
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return -EINVAL;
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/* Generate the trampoline. */
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tmp.brasl_opc = 0xc015; /* brasl %r1, shared */
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tmp.brasl_disp = (shared - (const char *)&trampoline->brasl_opc) / 2;
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tmp.interceptor = FTRACE_ADDR;
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tmp.rest_of_intercepted_function = rec->ip + sizeof(struct ftrace_insn);
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s390_kernel_write(trampoline, &tmp, sizeof(tmp));
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/* Generate a jump to the trampoline. */
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disp = ((char *)trampoline - (char *)rec->ip) / 2;
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insn = (struct ftrace_insn *)rec->ip;
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s390_kernel_write(&insn->disp, &disp, sizeof(disp));
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return 0;
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}
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static struct ftrace_hotpatch_trampoline *ftrace_get_trampoline(struct dyn_ftrace *rec)
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{
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struct ftrace_hotpatch_trampoline *trampoline;
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struct ftrace_insn insn;
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s64 disp;
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u16 opc;
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if (copy_from_kernel_nofault(&insn, (void *)rec->ip, sizeof(insn)))
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return ERR_PTR(-EFAULT);
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disp = (s64)insn.disp * 2;
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trampoline = (void *)(rec->ip + disp);
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if (get_kernel_nofault(opc, &trampoline->brasl_opc))
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return ERR_PTR(-EFAULT);
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if (opc != 0xc015)
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return ERR_PTR(-EINVAL);
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return trampoline;
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}
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int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
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unsigned long addr)
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{
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struct ftrace_hotpatch_trampoline *trampoline;
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u64 old;
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trampoline = ftrace_get_trampoline(rec);
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if (IS_ERR(trampoline))
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return PTR_ERR(trampoline);
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if (get_kernel_nofault(old, &trampoline->interceptor))
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return -EFAULT;
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if (old != old_addr)
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return -EINVAL;
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s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
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return 0;
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}
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static int ftrace_patch_branch_mask(void *addr, u16 expected, bool enable)
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{
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u16 old;
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u8 op;
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if (get_kernel_nofault(old, addr))
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return -EFAULT;
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if (old != expected)
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return -EINVAL;
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/* set mask field to all ones or zeroes */
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op = enable ? 0xf4 : 0x04;
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s390_kernel_write((char *)addr + 1, &op, sizeof(op));
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return 0;
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}
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int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
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unsigned long addr)
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{
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/* Expect brcl 0xf,... */
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return ftrace_patch_branch_mask((void *)rec->ip, 0xc0f4, false);
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}
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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struct ftrace_hotpatch_trampoline *trampoline;
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trampoline = ftrace_get_trampoline(rec);
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if (IS_ERR(trampoline))
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return PTR_ERR(trampoline);
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s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
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/* Expect brcl 0x0,... */
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return ftrace_patch_branch_mask((void *)rec->ip, 0xc004, true);
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}
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int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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ftrace_func = func;
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return 0;
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}
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void arch_ftrace_update_code(int command)
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{
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ftrace_modify_all_code(command);
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}
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void ftrace_arch_code_modify_post_process(void)
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{
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/*
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* Flush any pre-fetched instructions on all
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* CPUs to make the new code visible.
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*/
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text_poke_sync_lock();
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}
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#ifdef CONFIG_MODULES
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static int __init ftrace_plt_init(void)
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{
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const char *start, *end;
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ftrace_plt = module_alloc(PAGE_SIZE);
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if (!ftrace_plt)
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panic("cannot allocate ftrace plt\n");
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start = ftrace_shared_hotpatch_trampoline(&end);
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memcpy(ftrace_plt, start, end - start);
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set_memory_ro((unsigned long)ftrace_plt, 1);
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return 0;
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}
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device_initcall(ftrace_plt_init);
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#endif /* CONFIG_MODULES */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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/*
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* Hook the return address and push it in the stack of return addresses
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* in current thread info.
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*/
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unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
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unsigned long ip)
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{
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if (unlikely(ftrace_graph_is_dead()))
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goto out;
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if (unlikely(atomic_read(¤t->tracing_graph_pause)))
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goto out;
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ip -= MCOUNT_INSN_SIZE;
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if (!function_graph_enter(ra, ip, 0, (void *) sp))
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ra = (unsigned long) return_to_handler;
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out:
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return ra;
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}
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NOKPROBE_SYMBOL(prepare_ftrace_return);
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/*
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* Patch the kernel code at ftrace_graph_caller location. The instruction
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* there is branch relative on condition. To enable the ftrace graph code
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* block, we simply patch the mask field of the instruction to zero and
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* turn the instruction into a nop.
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* To disable the ftrace graph code the mask field will be patched to
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* all ones, which turns the instruction into an unconditional branch.
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*/
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int ftrace_enable_ftrace_graph_caller(void)
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{
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int rc;
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/* Expect brc 0xf,... */
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rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false);
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if (rc)
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return rc;
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text_poke_sync_lock();
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return 0;
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}
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int ftrace_disable_ftrace_graph_caller(void)
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{
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int rc;
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/* Expect brc 0x0,... */
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rc = ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true);
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if (rc)
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return rc;
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text_poke_sync_lock();
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return 0;
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}
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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#ifdef CONFIG_KPROBES_ON_FTRACE
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void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
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struct ftrace_ops *ops, struct ftrace_regs *fregs)
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{
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struct kprobe_ctlblk *kcb;
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struct pt_regs *regs;
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struct kprobe *p;
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int bit;
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bit = ftrace_test_recursion_trylock(ip, parent_ip);
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if (bit < 0)
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return;
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regs = ftrace_get_regs(fregs);
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p = get_kprobe((kprobe_opcode_t *)ip);
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if (!regs || unlikely(!p) || kprobe_disabled(p))
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goto out;
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if (kprobe_running()) {
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kprobes_inc_nmissed_count(p);
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goto out;
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}
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__this_cpu_write(current_kprobe, p);
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kcb = get_kprobe_ctlblk();
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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instruction_pointer_set(regs, ip);
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if (!p->pre_handler || !p->pre_handler(p, regs)) {
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instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
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if (unlikely(p->post_handler)) {
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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p->post_handler(p, regs, 0);
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}
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}
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__this_cpu_write(current_kprobe, NULL);
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out:
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ftrace_test_recursion_unlock(bit);
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}
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NOKPROBE_SYMBOL(kprobe_ftrace_handler);
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int arch_prepare_kprobe_ftrace(struct kprobe *p)
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{
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p->ainsn.insn = NULL;
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return 0;
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}
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#endif
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