/** * @file backtrace.c * * @remark Copyright 2002 OProfile authors * @remark Read the file COPYING * * @author John Levon * @author David Smith */ #include <linux/oprofile.h> #include <linux/sched.h> #include <linux/mm.h> #include <asm/ptrace.h> #include <asm/uaccess.h> struct frame_head { struct frame_head * ebp; unsigned long ret; } __attribute__((packed)); static struct frame_head * dump_kernel_backtrace(struct frame_head * head) { oprofile_add_trace(head->ret); /* frame pointers should strictly progress back up the stack * (towards higher addresses) */ if (head >= head->ebp) return NULL; return head->ebp; } static struct frame_head * dump_user_backtrace(struct frame_head * head) { struct frame_head bufhead[2]; /* Also check accessibility of one struct frame_head beyond */ if (!access_ok(VERIFY_READ, head, sizeof(bufhead))) return NULL; if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead))) return NULL; oprofile_add_trace(bufhead[0].ret); /* frame pointers should strictly progress back up the stack * (towards higher addresses) */ if (head >= bufhead[0].ebp) return NULL; return bufhead[0].ebp; } /* * | | /\ Higher addresses * | | * --------------- stack base (address of current_thread_info) * | thread info | * . . * | stack | * --------------- saved regs->ebp value if valid (frame_head address) * . . * --------------- saved regs->rsp value if x86_64 * | | * --------------- struct pt_regs * stored on stack if 32-bit * | | * . . * | | * --------------- %esp * | | * | | \/ Lower addresses * * Thus, regs (or regs->rsp for x86_64) <-> stack base restricts the * valid(ish) ebp values. Note: (1) for x86_64, NMI and several other * exceptions use special stacks, maintained by the interrupt stack table * (IST). These stacks are set up in trap_init() in * arch/x86_64/kernel/traps.c. Thus, for x86_64, regs now does not point * to the kernel stack; instead, it points to some location on the NMI * stack. On the other hand, regs->rsp is the stack pointer saved when the * NMI occurred. (2) For 32-bit, regs->esp is not valid because the * processor does not save %esp on the kernel stack when interrupts occur * in the kernel mode. */ #ifdef CONFIG_FRAME_POINTER static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs) { unsigned long headaddr = (unsigned long)head; #ifdef CONFIG_X86_64 unsigned long stack = (unsigned long)regs->rsp; #else unsigned long stack = (unsigned long)regs; #endif unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE; return headaddr > stack && headaddr < stack_base; } #else /* without fp, it's just junk */ static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs) { return 0; } #endif void x86_backtrace(struct pt_regs * const regs, unsigned int depth) { struct frame_head *head; #ifdef CONFIG_X86_64 head = (struct frame_head *)regs->rbp; #else head = (struct frame_head *)regs->ebp; #endif if (!user_mode_vm(regs)) { while (depth-- && valid_kernel_stack(head, regs)) head = dump_kernel_backtrace(head); return; } while (depth-- && head) head = dump_user_backtrace(head); }