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