313 lines
7.3 KiB
C
313 lines
7.3 KiB
C
/*
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* Dynamic function tracing support.
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*
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* Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
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* Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
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*
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* For licencing details, see COPYING.
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*
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* Defines low-level handling of mcount calls when the kernel
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* is compiled with the -pg flag. When using dynamic ftrace, the
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* mcount call-sites get patched with NOP till they are enabled.
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* All code mutation routines here are called under stop_machine().
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*/
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#include <linux/ftrace.h>
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#include <linux/uaccess.h>
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#include <linux/module.h>
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#include <linux/stop_machine.h>
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#include <asm/cacheflush.h>
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#include <asm/opcodes.h>
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#include <asm/ftrace.h>
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#include <asm/insn.h>
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#include <asm/set_memory.h>
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#include <asm/stacktrace.h>
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#include <asm/patch.h>
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/*
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* The compiler emitted profiling hook consists of
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*
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* PUSH {LR}
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* BL __gnu_mcount_nc
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*
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* To turn this combined sequence into a NOP, we need to restore the value of
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* SP before the PUSH. Let's use an ADD rather than a POP into LR, as LR is not
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* modified anyway, and reloading LR from memory is highly likely to be less
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* efficient.
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*/
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#ifdef CONFIG_THUMB2_KERNEL
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#define NOP 0xf10d0d04 /* add.w sp, sp, #4 */
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#else
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#define NOP 0xe28dd004 /* add sp, sp, #4 */
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#endif
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#ifdef CONFIG_DYNAMIC_FTRACE
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static int __ftrace_modify_code(void *data)
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{
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int *command = data;
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ftrace_modify_all_code(*command);
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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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stop_machine(__ftrace_modify_code, &command, NULL);
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}
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static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
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{
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return NOP;
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}
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void ftrace_caller_from_init(void);
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void ftrace_regs_caller_from_init(void);
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static unsigned long __ref adjust_address(struct dyn_ftrace *rec,
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unsigned long addr)
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{
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if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE) ||
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system_state >= SYSTEM_FREEING_INITMEM ||
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likely(!is_kernel_inittext(rec->ip)))
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return addr;
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if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) ||
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addr == (unsigned long)&ftrace_caller)
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return (unsigned long)&ftrace_caller_from_init;
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return (unsigned long)&ftrace_regs_caller_from_init;
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}
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int ftrace_arch_code_modify_prepare(void)
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{
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return 0;
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}
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int ftrace_arch_code_modify_post_process(void)
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{
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/* Make sure any TLB misses during machine stop are cleared. */
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flush_tlb_all();
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return 0;
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}
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static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
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bool warn)
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{
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return arm_gen_branch_link(pc, addr, warn);
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}
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static int ftrace_modify_code(unsigned long pc, unsigned long old,
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unsigned long new, bool validate)
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{
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unsigned long replaced;
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if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
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old = __opcode_to_mem_thumb32(old);
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else
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old = __opcode_to_mem_arm(old);
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if (validate) {
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if (copy_from_kernel_nofault(&replaced, (void *)pc,
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MCOUNT_INSN_SIZE))
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return -EFAULT;
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if (replaced != old)
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return -EINVAL;
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}
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__patch_text((void *)pc, new);
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return 0;
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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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unsigned long pc;
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unsigned long new;
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int ret;
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pc = (unsigned long)&ftrace_call;
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new = ftrace_call_replace(pc, (unsigned long)func, true);
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ret = ftrace_modify_code(pc, 0, new, false);
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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if (!ret) {
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pc = (unsigned long)&ftrace_regs_call;
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new = ftrace_call_replace(pc, (unsigned long)func, true);
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ret = ftrace_modify_code(pc, 0, new, false);
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}
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#endif
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return ret;
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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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unsigned long new, old;
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unsigned long ip = rec->ip;
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unsigned long aaddr = adjust_address(rec, addr);
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struct module *mod = NULL;
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#ifdef CONFIG_ARM_MODULE_PLTS
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mod = rec->arch.mod;
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#endif
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old = ftrace_nop_replace(rec);
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new = ftrace_call_replace(ip, aaddr, !mod);
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#ifdef CONFIG_ARM_MODULE_PLTS
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if (!new && mod) {
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aaddr = get_module_plt(mod, ip, aaddr);
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new = ftrace_call_replace(ip, aaddr, true);
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}
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#endif
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return ftrace_modify_code(rec->ip, old, new, true);
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}
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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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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unsigned long new, old;
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unsigned long ip = rec->ip;
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old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true);
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new = ftrace_call_replace(ip, adjust_address(rec, addr), true);
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return ftrace_modify_code(rec->ip, old, new, true);
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}
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#endif
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int ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned long aaddr = adjust_address(rec, addr);
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unsigned long ip = rec->ip;
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unsigned long old;
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unsigned long new;
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int ret;
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#ifdef CONFIG_ARM_MODULE_PLTS
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/* mod is only supplied during module loading */
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if (!mod)
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mod = rec->arch.mod;
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else
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rec->arch.mod = mod;
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#endif
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old = ftrace_call_replace(ip, aaddr,
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!IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
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#ifdef CONFIG_ARM_MODULE_PLTS
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if (!old && mod) {
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aaddr = get_module_plt(mod, ip, aaddr);
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old = ftrace_call_replace(ip, aaddr, true);
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}
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#endif
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new = ftrace_nop_replace(rec);
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/*
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* Locations in .init.text may call __gnu_mcount_mc via a linker
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* emitted veneer if they are too far away from its implementation, and
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* so validation may fail spuriously in such cases. Let's work around
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* this by omitting those from validation.
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*/
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ret = ftrace_modify_code(ip, old, new, !is_kernel_inittext(ip));
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return ret;
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}
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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asmlinkage
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void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
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unsigned long frame_pointer,
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unsigned long stack_pointer)
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{
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unsigned long return_hooker = (unsigned long) &return_to_handler;
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unsigned long old;
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if (unlikely(atomic_read(¤t->tracing_graph_pause)))
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return;
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if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER)) {
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/* FP points one word below parent's top of stack */
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frame_pointer += 4;
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} else {
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struct stackframe frame = {
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.fp = frame_pointer,
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.sp = stack_pointer,
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.lr = self_addr,
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.pc = self_addr,
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};
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if (unwind_frame(&frame) < 0)
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return;
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if (frame.lr != self_addr)
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parent = frame.lr_addr;
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frame_pointer = frame.sp;
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}
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old = *parent;
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*parent = return_hooker;
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if (function_graph_enter(old, self_addr, frame_pointer, NULL))
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*parent = old;
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}
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#ifdef CONFIG_DYNAMIC_FTRACE
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extern unsigned long ftrace_graph_call;
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extern unsigned long ftrace_graph_call_old;
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extern void ftrace_graph_caller_old(void);
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extern unsigned long ftrace_graph_regs_call;
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extern void ftrace_graph_regs_caller(void);
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static int __ftrace_modify_caller(unsigned long *callsite,
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void (*func) (void), bool enable)
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{
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unsigned long caller_fn = (unsigned long) func;
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unsigned long pc = (unsigned long) callsite;
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unsigned long branch = arm_gen_branch(pc, caller_fn);
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unsigned long nop = arm_gen_nop();
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unsigned long old = enable ? nop : branch;
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unsigned long new = enable ? branch : nop;
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return ftrace_modify_code(pc, old, new, true);
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}
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static int ftrace_modify_graph_caller(bool enable)
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{
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int ret;
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ret = __ftrace_modify_caller(&ftrace_graph_call,
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ftrace_graph_caller,
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enable);
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#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
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if (!ret)
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ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
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ftrace_graph_regs_caller,
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enable);
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#endif
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return ret;
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}
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int ftrace_enable_ftrace_graph_caller(void)
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{
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return ftrace_modify_graph_caller(true);
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}
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int ftrace_disable_ftrace_graph_caller(void)
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{
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return ftrace_modify_graph_caller(false);
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}
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#endif /* CONFIG_DYNAMIC_FTRACE */
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#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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