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Release 4.11 arch/arm/kernel/unwind.c

Directory: arch/arm/kernel
/*
 * arch/arm/kernel/unwind.c
 *
 * Copyright (C) 2008 ARM Limited
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 *
 * Stack unwinding support for ARM
 *
 * An ARM EABI version of gcc is required to generate the unwind
 * tables. For information about the structure of the unwind tables,
 * see "Exception Handling ABI for the ARM Architecture" at:
 *
 * http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html
 */

#ifndef __CHECKER__
#if !defined (__ARM_EABI__)
#warning Your compiler does not have EABI support.
#warning    ARM unwind is known to compile only with EABI compilers.
#warning    Change compiler or disable ARM_UNWIND option.
#elif (__GNUC__ == 4 && __GNUC_MINOR__ <= 2) && !defined(__clang__)
#warning Your compiler is too buggy; it is known to not compile ARM unwind support.
#warning    Change compiler or disable ARM_UNWIND option.
#endif
#endif /* __CHECKER__ */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/list.h>

#include <asm/stacktrace.h>
#include <asm/traps.h>
#include <asm/unwind.h>

/* Dummy functions to avoid linker complaints */

void __aeabi_unwind_cpp_pr0(void) { }

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; EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
void __aeabi_unwind_cpp_pr1(void) { }

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; EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
void __aeabi_unwind_cpp_pr2(void) { }

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; EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2); struct unwind_ctrl_block { unsigned long vrs[16]; /* virtual register set */ const unsigned long *insn; /* pointer to the current instructions word */ unsigned long sp_high; /* highest value of sp allowed */ /* * 1 : check for stack overflow for each register pop. * 0 : save overhead if there is plenty of stack remaining. */ int check_each_pop; int entries; /* number of entries left to interpret */ int byte; /* current byte number in the instructions word */ }; enum regs { #ifdef CONFIG_THUMB2_KERNEL FP = 7, #else FP = 11, #endif SP = 13, LR = 14, PC = 15 }; extern const struct unwind_idx __start_unwind_idx[]; static const struct unwind_idx *__origin_unwind_idx; extern const struct unwind_idx __stop_unwind_idx[]; static DEFINE_SPINLOCK(unwind_lock); static LIST_HEAD(unwind_tables); /* Convert a prel31 symbol to an absolute address */ #define prel31_to_addr(ptr) \ ({ \ /* sign-extend to 32 bits */ \ long offset = (((long)*(ptr)) << 1) >> 1; \ (unsigned long)(ptr) + offset; \ }) /* * Binary search in the unwind index. The entries are * guaranteed to be sorted in ascending order by the linker. * * start = first entry * origin = first entry with positive offset (or stop if there is no such entry) * stop - 1 = last entry */
static const struct unwind_idx *search_index(unsigned long addr, const struct unwind_idx *start, const struct unwind_idx *origin, const struct unwind_idx *stop) { unsigned long addr_prel31; pr_debug("%s(%08lx, %p, %p, %p)\n", __func__, addr, start, origin, stop); /* * only search in the section with the matching sign. This way the * prel31 numbers can be compared as unsigned longs. */ if (addr < (unsigned long)start) /* negative offsets: [start; origin) */ stop = origin; else /* positive offsets: [origin; stop) */ start = origin; /* prel31 for address relavive to start */ addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff; while (start < stop - 1) { const struct unwind_idx *mid = start + ((stop - start) >> 1); /* * As addr_prel31 is relative to start an offset is needed to * make it relative to mid. */ if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) < mid->addr_offset) stop = mid; else { /* keep addr_prel31 relative to start */ addr_prel31 -= ((unsigned long)mid - (unsigned long)start); start = mid; } } if (likely(start->addr_offset <= addr_prel31)) return start; else { pr_warn("unwind: Unknown symbol address %08lx\n", addr); return NULL; } }

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static const struct unwind_idx *unwind_find_origin( const struct unwind_idx *start, const struct unwind_idx *stop) { pr_debug("%s(%p, %p)\n", __func__, start, stop); while (start < stop) { const struct unwind_idx *mid = start + ((stop - start) >> 1); if (mid->addr_offset >= 0x40000000) /* negative offset */ start = mid + 1; else /* positive offset */ stop = mid; } pr_debug("%s -> %p\n", __func__, stop); return stop; }

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static const struct unwind_idx *unwind_find_idx(unsigned long addr) { const struct unwind_idx *idx = NULL; unsigned long flags; pr_debug("%s(%08lx)\n", __func__, addr); if (core_kernel_text(addr)) { if (unlikely(!__origin_unwind_idx)) __origin_unwind_idx = unwind_find_origin(__start_unwind_idx, __stop_unwind_idx); /* main unwind table */ idx = search_index(addr, __start_unwind_idx, __origin_unwind_idx, __stop_unwind_idx); } else { /* module unwind tables */ struct unwind_table *table; spin_lock_irqsave(&unwind_lock, flags); list_for_each_entry(table, &unwind_tables, list) { if (addr >= table->begin_addr && addr < table->end_addr) { idx = search_index(addr, table->start, table->origin, table->stop); /* Move-to-front to exploit common traces */ list_move(&table->list, &unwind_tables); break; } } spin_unlock_irqrestore(&unwind_lock, flags); } pr_debug("%s: idx = %p\n", __func__, idx); return idx; }

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static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl) { unsigned long ret; if (ctrl->entries <= 0) { pr_warn("unwind: Corrupt unwind table\n"); return 0; } ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff; if (ctrl->byte == 0) { ctrl->insn++; ctrl->entries--; ctrl->byte = 3; } else ctrl->byte--; return ret; }

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/* Before poping a register check whether it is feasible or not */
static int unwind_pop_register(struct unwind_ctrl_block *ctrl, unsigned long **vsp, unsigned int reg) { if (unlikely(ctrl->check_each_pop)) if (*vsp >= (unsigned long *)ctrl->sp_high) return -URC_FAILURE; ctrl->vrs[reg] = *(*vsp)++; return URC_OK; }

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/* Helper functions to execute the instructions */
static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl, unsigned long mask) { unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; int load_sp, reg = 4; load_sp = mask & (1 << (13 - 4)); while (mask) { if (mask & 1) if (unwind_pop_register(ctrl, &vsp, reg)) return -URC_FAILURE; mask >>= 1; reg++; } if (!load_sp) ctrl->vrs[SP] = (unsigned long)vsp; return URC_OK; }

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static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl, unsigned long insn) { unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; int reg; /* pop R4-R[4+bbb] */ for (reg = 4; reg <= 4 + (insn & 7); reg++) if (unwind_pop_register(ctrl, &vsp, reg)) return -URC_FAILURE; if (insn & 0x8) if (unwind_pop_register(ctrl, &vsp, 14)) return -URC_FAILURE; ctrl->vrs[SP] = (unsigned long)vsp; return URC_OK; }

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static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl, unsigned long mask) { unsigned long *vsp = (unsigned long *)ctrl->vrs[SP]; int reg = 0; /* pop R0-R3 according to mask */ while (mask) { if (mask & 1) if (unwind_pop_register(ctrl, &vsp, reg)) return -URC_FAILURE; mask >>= 1; reg++; } ctrl->vrs[SP] = (unsigned long)vsp; return URC_OK; }

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/* * Execute the current unwind instruction. */
static int unwind_exec_insn(struct unwind_ctrl_block *ctrl) { unsigned long insn = unwind_get_byte(ctrl); int ret = URC_OK; pr_debug("%s: insn = %08lx\n", __func__, insn); if ((insn & 0xc0) == 0x00) ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4; else if ((insn & 0xc0) == 0x40) ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4; else if ((insn & 0xf0) == 0x80) { unsigned long mask; insn = (insn << 8) | unwind_get_byte(ctrl); mask = insn & 0x0fff; if (mask == 0) { pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n", insn); return -URC_FAILURE; } ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask); if (ret) goto error; } else if ((insn & 0xf0) == 0x90 && (insn & 0x0d) != 0x0d) ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f]; else if ((insn & 0xf0) == 0xa0) { ret = unwind_exec_pop_r4_to_rN(ctrl, insn); if (ret) goto error; } else if (insn == 0xb0) { if (ctrl->vrs[PC] == 0) ctrl->vrs[PC] = ctrl->vrs[LR]; /* no further processing */ ctrl->entries = 0; } else if (insn == 0xb1) { unsigned long mask = unwind_get_byte(ctrl); if (mask == 0 || mask & 0xf0) { pr_warn("unwind: Spare encoding %04lx\n", (insn << 8) | mask); return -URC_FAILURE; } ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask); if (ret) goto error; } else if (insn == 0xb2) { unsigned long uleb128 = unwind_get_byte(ctrl); ctrl->vrs[SP] += 0x204 + (uleb128 << 2); } else { pr_warn("unwind: Unhandled instruction %02lx\n", insn); return -URC_FAILURE; } pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__, ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]); error: return ret; }

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/* * Unwind a single frame starting with *sp for the symbol at *pc. It * updates the *pc and *sp with the new values. */
int unwind_frame(struct stackframe *frame) { unsigned long low; const struct unwind_idx *idx; struct unwind_ctrl_block ctrl; /* store the highest address on the stack to avoid crossing it*/ low = frame->sp; ctrl.sp_high = ALIGN(low, THREAD_SIZE); pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__, frame->pc, frame->lr, frame->sp); if (!kernel_text_address(frame->pc)) return -URC_FAILURE; idx = unwind_find_idx(frame->pc); if (!idx) { pr_warn("unwind: Index not found %08lx\n", frame->pc); return -URC_FAILURE; } ctrl.vrs[FP] = frame->fp; ctrl.vrs[SP] = frame->sp; ctrl.vrs[LR] = frame->lr; ctrl.vrs[PC] = 0; if (idx->insn == 1) /* can't unwind */ return -URC_FAILURE; else if ((idx->insn & 0x80000000) == 0) /* prel31 to the unwind table */ ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn); else if ((idx->insn & 0xff000000) == 0x80000000) /* only personality routine 0 supported in the index */ ctrl.insn = &idx->insn; else { pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n", idx->insn, idx); return -URC_FAILURE; } /* check the personality routine */ if ((*ctrl.insn & 0xff000000) == 0x80000000) { ctrl.byte = 2; ctrl.entries = 1; } else if ((*ctrl.insn & 0xff000000) == 0x81000000) { ctrl.byte = 1; ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16); } else { pr_warn("unwind: Unsupported personality routine %08lx at %p\n", *ctrl.insn, ctrl.insn); return -URC_FAILURE; } ctrl.check_each_pop = 0; while (ctrl.entries > 0) { int urc; if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs)) ctrl.check_each_pop = 1; urc = unwind_exec_insn(&ctrl); if (urc < 0) return urc; if (ctrl.vrs[SP] < low || ctrl.vrs[SP] >= ctrl.sp_high) return -URC_FAILURE; } if (ctrl.vrs[PC] == 0) ctrl.vrs[PC] = ctrl.vrs[LR]; /* check for infinite loop */ if (frame->pc == ctrl.vrs[PC]) return -URC_FAILURE; frame->fp = ctrl.vrs[FP]; frame->sp = ctrl.vrs[SP]; frame->lr = ctrl.vrs[LR]; frame->pc = ctrl.vrs[PC]; return URC_OK; }

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void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk) { struct stackframe frame; pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk); if (!tsk) tsk = current; if (regs) { arm_get_current_stackframe(regs, &frame); /* PC might be corrupted, use LR in that case. */ if (!kernel_text_address(regs->ARM_pc)) frame.pc = regs->ARM_lr; } else if (tsk == current) { frame.fp = (unsigned long)__builtin_frame_address(0); frame.sp = current_stack_pointer; frame.lr = (unsigned long)__builtin_return_address(0); frame.pc = (unsigned long)unwind_backtrace; } else { /* task blocked in __switch_to */ frame.fp = thread_saved_fp(tsk); frame.sp = thread_saved_sp(tsk); /* * The function calling __switch_to cannot be a leaf function * so LR is recovered from the stack. */ frame.lr = 0; frame.pc = thread_saved_pc(tsk); } while (1) { int urc; unsigned long where = frame.pc; urc = unwind_frame(&frame); if (urc < 0) break; dump_backtrace_entry(where, frame.pc, frame.sp - 4); } }

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struct unwind_table *unwind_table_add(unsigned long start, unsigned long size, unsigned long text_addr, unsigned long text_size) { unsigned long flags; struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL); pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size, text_addr, text_size); if (!tab) return tab; tab->start = (const struct unwind_idx *)start; tab->stop = (const struct unwind_idx *)(start + size); tab->origin = unwind_find_origin(tab->start, tab->stop); tab->begin_addr = text_addr; tab->end_addr = text_addr + text_size; spin_lock_irqsave(&unwind_lock, flags); list_add_tail(&tab->list, &unwind_tables); spin_unlock_irqrestore(&unwind_lock, flags); return tab; }

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void unwind_table_del(struct unwind_table *tab) { unsigned long flags; if (!tab) return; spin_lock_irqsave(&unwind_lock, flags); list_del(&tab->list); spin_unlock_irqrestore(&unwind_lock, flags); kfree(tab); }

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Directory: arch/arm/kernel
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