cregit-Linux how code gets into the kernel

Release 4.14 arch/metag/kernel/stacktrace.c

#include <linux/export.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/task_stack.h>
#include <linux/stacktrace.h>

#include <asm/stacktrace.h>

#if defined(CONFIG_FRAME_POINTER)

#ifdef CONFIG_KALLSYMS
#include <linux/kallsyms.h>
#include <linux/module.h>


static unsigned long tbi_boing_addr;

static unsigned long tbi_boing_size;


static void tbi_boing_init(void) { /* We need to know where TBIBoingVec is and it's size */ unsigned long size; unsigned long offset; char modname[MODULE_NAME_LEN]; char name[KSYM_NAME_LEN]; tbi_boing_addr = kallsyms_lookup_name("___TBIBoingVec"); if (!tbi_boing_addr) tbi_boing_addr = 1; else if (!lookup_symbol_attrs(tbi_boing_addr, &size, &offset, modname, name)) tbi_boing_size = size; }

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#endif /* * Unwind the current stack frame and store the new register values in the * structure passed as argument. Unwinding is equivalent to a function return, * hence the new PC value rather than LR should be used for backtrace. */
int notrace unwind_frame(struct stackframe *frame) { struct metag_frame *fp = (struct metag_frame *)frame->fp; unsigned long lr; unsigned long fpnew; if (frame->fp & 0x7) return -EINVAL; fpnew = fp->fp; lr = fp->lr - 4; #ifdef CONFIG_KALLSYMS /* If we've reached TBIBoingVec then we're at an interrupt * entry point or a syscall entry point. The frame pointer * points to a pt_regs which can be used to continue tracing on * the other side of the boing. */ if (!tbi_boing_addr) tbi_boing_init(); if (tbi_boing_size && lr >= tbi_boing_addr && lr < tbi_boing_addr + tbi_boing_size) { struct pt_regs *regs = (struct pt_regs *)fpnew; if (user_mode(regs)) return -EINVAL; fpnew = regs->ctx.AX[1].U0; lr = regs->ctx.DX[4].U1; } #endif /* stack grows up, so frame pointers must decrease */ if (fpnew < (ALIGN_DOWN((unsigned long)fp, THREAD_SIZE) + sizeof(struct thread_info)) || fpnew >= (unsigned long)fp) return -EINVAL; /* restore the registers from the stack frame */ frame->fp = fpnew; frame->pc = lr; return 0; }

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#else
int notrace unwind_frame(struct stackframe *frame) { struct metag_frame *sp = (struct metag_frame *)frame->sp; if (frame->sp & 0x7) return -EINVAL; while (!kstack_end(sp)) { unsigned long addr = sp->lr - 4; sp--; if (__kernel_text_address(addr)) { frame->sp = (unsigned long)sp; frame->pc = addr; return 0; } } return -EINVAL; }

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#endif
void notrace walk_stackframe(struct stackframe *frame, int (*fn)(struct stackframe *, void *), void *data) { while (1) { int ret; if (fn(frame, data)) break; ret = unwind_frame(frame); if (ret < 0) break; } }

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EXPORT_SYMBOL(walk_stackframe); #ifdef CONFIG_STACKTRACE struct stack_trace_data { struct stack_trace *trace; unsigned int no_sched_functions; unsigned int skip; };
static int save_trace(struct stackframe *frame, void *d) { struct stack_trace_data *data = d; struct stack_trace *trace = data->trace; unsigned long addr = frame->pc; if (data->no_sched_functions && in_sched_functions(addr)) return 0; if (data->skip) { data->skip--; return 0; } trace->entries[trace->nr_entries++] = addr; return trace->nr_entries >= trace->max_entries; }

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void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) { struct stack_trace_data data; struct stackframe frame; data.trace = trace; data.skip = trace->skip; if (tsk != current) { #ifdef CONFIG_SMP /* * What guarantees do we have here that 'tsk' is not * running on another CPU? For now, ignore it as we * can't guarantee we won't explode. */ if (trace->nr_entries < trace->max_entries) trace->entries[trace->nr_entries++] = ULONG_MAX; return; #else data.no_sched_functions = 1; frame.fp = thread_saved_fp(tsk); frame.sp = thread_saved_sp(tsk); frame.lr = 0; /* recovered from the stack */ frame.pc = thread_saved_pc(tsk); #endif } else { register unsigned long current_sp asm ("A0StP"); data.no_sched_functions = 0; frame.fp = (unsigned long)__builtin_frame_address(0); frame.sp = current_sp; frame.lr = (unsigned long)__builtin_return_address(0); frame.pc = (unsigned long)save_stack_trace_tsk; } walk_stackframe(&frame, save_trace, &data); if (trace->nr_entries < trace->max_entries) trace->entries[trace->nr_entries++] = ULONG_MAX; }

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void save_stack_trace(struct stack_trace *trace) { save_stack_trace_tsk(current, trace); }

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EXPORT_SYMBOL_GPL(save_stack_trace); #endif

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