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- /*
- * Libbacktrace
- * Copyright 2015 Stephen Street <stephen@redrocketcomputing.com>
- *
- * This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at https://mozilla.org/MPL/2.0/.
- *
- * This library was modified, some bugs fixed, stack address validated
- * and adapted to be used in Marlin 3D printer firmware as backtracer
- * for exceptions for debugging purposes in 2018 by Eduardo José Tagle.
- */
-
- #if defined(__arm__) || defined(__thumb__)
-
- #include "unwarmbytab.h"
-
- #include <stdint.h>
- #include <string.h>
-
- /* These symbols point to the unwind index and should be provide by the linker script */
- extern "C" const UnwTabEntry __exidx_start[];
- extern "C" const UnwTabEntry __exidx_end[];
-
- /* This prevents the linking of libgcc unwinder code */
- void __aeabi_unwind_cpp_pr0() {};
- void __aeabi_unwind_cpp_pr1() {};
- void __aeabi_unwind_cpp_pr2() {};
-
- static inline __attribute__((always_inline)) uint32_t prel31_to_addr(const uint32_t *prel31) {
- uint32_t offset = (((uint32_t)(*prel31)) << 1) >> 1;
- return ((uint32_t)prel31 + offset) & 0x7FFFFFFF;
- }
-
- static const UnwTabEntry *UnwTabSearchIndex(const UnwTabEntry *start, const UnwTabEntry *end, uint32_t ip) {
- const UnwTabEntry *middle;
-
- /* Perform a binary search of the unwind index */
- while (start < end - 1) {
- middle = start + ((end - start + 1) >> 1);
- if (ip < prel31_to_addr(&middle->addr_offset))
- end = middle;
- else
- start = middle;
- }
- return start;
- }
-
- /*
- * Get the function name or nullptr if not found
- */
- static const char *UnwTabGetFunctionName(const UnwindCallbacks *cb, uint32_t address) {
- uint32_t flag_word = 0;
- if (!cb->readW(address-4,&flag_word))
- return nullptr;
-
- if ((flag_word & 0xFF000000) == 0xFF000000) {
- return (const char *)(address - 4 - (flag_word & 0x00FFFFFF));
- }
- return nullptr;
- }
-
- /**
- * Get the next frame unwinding instruction
- *
- * Return either the instruction or -1 to signal no more instructions
- * are available
- */
- static int UnwTabGetNextInstruction(const UnwindCallbacks *cb, UnwTabState *ucb) {
- int instruction;
-
- /* Are there more instructions */
- if (ucb->remaining == 0)
- return -1;
-
- /* Extract the current instruction */
- uint32_t v = 0;
- if (!cb->readW(ucb->current, &v))
- return -1;
- instruction = (v >> (ucb->byte << 3)) & 0xFF;
-
- /* Move the next byte */
- --ucb->byte;
- if (ucb->byte < 0) {
- ucb->current += 4;
- ucb->byte = 3;
- }
- --ucb->remaining;
-
- return instruction;
- }
-
- /**
- * Initialize the frame unwinding state
- */
- static UnwResult UnwTabStateInit(const UnwindCallbacks *cb, UnwTabState *ucb, uint32_t instructions, const UnwindFrame *frame) {
-
- /* Initialize control block */
- memset(ucb, 0, sizeof(UnwTabState));
- ucb->current = instructions;
-
- /* Is a short unwind description */
- uint32_t v = 0;
- if (!cb->readW(instructions, &v))
- return UNWIND_DREAD_W_FAIL;
-
- if ((v & 0xFF000000) == 0x80000000) {
- ucb->remaining = 3;
- ucb->byte = 2;
- /* Is a long unwind description */
- } else if ((v & 0xFF000000) == 0x81000000) {
- ucb->remaining = ((v & 0x00FF0000) >> 14) + 2;
- ucb->byte = 1;
- } else
- return UNWIND_UNSUPPORTED_DWARF_PERSONALITY;
-
- /* Initialize the virtual register set */
- ucb->vrs[7] = frame->fp;
- ucb->vrs[13] = frame->sp;
- ucb->vrs[14] = frame->lr;
- ucb->vrs[15] = 0;
-
- /* All good */
- return UNWIND_SUCCESS;
- }
-
- /*
- * Execute unwinding instructions
- */
- static UnwResult UnwTabExecuteInstructions(const UnwindCallbacks *cb, UnwTabState *ucb) {
-
- int instruction;
- uint32_t mask;
- uint32_t reg;
- uint32_t vsp;
-
- /* Consume all instruction byte */
- while ((instruction = UnwTabGetNextInstruction(cb, ucb)) != -1) {
-
- if ((instruction & 0xC0) == 0x00) { // ARM_EXIDX_CMD_DATA_POP
- /* vsp = vsp + (xxxxxx << 2) + 4 */
- ucb->vrs[13] += ((instruction & 0x3F) << 2) + 4;
- } else
- if ((instruction & 0xC0) == 0x40) { // ARM_EXIDX_CMD_DATA_PUSH
- /* vsp = vsp - (xxxxxx << 2) - 4 */
- ucb->vrs[13] -= ((instruction & 0x3F) << 2) - 4;
- } else
- if ((instruction & 0xF0) == 0x80) {
- /* pop under mask {r15-r12},{r11-r4} or refuse to unwind */
- instruction = instruction << 8 | UnwTabGetNextInstruction(cb, ucb);
-
- /* Check for refuse to unwind */
- if (instruction == 0x8000) // ARM_EXIDX_CMD_REFUSED
- return UNWIND_REFUSED;
-
- /* Pop registers using mask */ // ARM_EXIDX_CMD_REG_POP
- vsp = ucb->vrs[13];
- mask = instruction & 0xFFF;
-
- reg = 4;
- while (mask) {
- if ((mask & 1) != 0) {
- uint32_t v;
- if (!cb->readW(vsp,&v))
- return UNWIND_DREAD_W_FAIL;
- ucb->vrs[reg] = v;
- v += 4;
- }
- mask >>= 1;
- ++reg;
- }
-
- /* Patch up the vrs sp if it was in the mask */
- if ((instruction & (1 << (13 - 4))) != 0)
- ucb->vrs[13] = vsp;
-
- } else
- if ((instruction & 0xF0) == 0x90 && // ARM_EXIDX_CMD_REG_TO_SP
- instruction != 0x9D &&
- instruction != 0x9F) {
- /* vsp = r[nnnn] */
- ucb->vrs[13] = ucb->vrs[instruction & 0x0F];
- } else
- if ((instruction & 0xF0) == 0xA0) { // ARM_EXIDX_CMD_REG_POP
- /* pop r4-r[4+nnn] or pop r4-r[4+nnn], r14*/
- vsp = ucb->vrs[13];
-
- for (reg = 4; reg <= uint32_t((instruction & 0x07) + 4); ++reg) {
- uint32_t v;
- if (!cb->readW(vsp,&v))
- return UNWIND_DREAD_W_FAIL;
-
- ucb->vrs[reg] = v;
- vsp += 4;
- }
-
- if (instruction & 0x08) { // ARM_EXIDX_CMD_REG_POP
- uint32_t v;
- if (!cb->readW(vsp,&v))
- return UNWIND_DREAD_W_FAIL;
- ucb->vrs[14] = v;
- vsp += 4;
- }
-
- ucb->vrs[13] = vsp;
-
- } else
- if (instruction == 0xB0) { // ARM_EXIDX_CMD_FINISH
- /* finished */
- if (ucb->vrs[15] == 0)
- ucb->vrs[15] = ucb->vrs[14];
-
- /* All done unwinding */
- return UNWIND_SUCCESS;
-
- } else
- if (instruction == 0xB1) { // ARM_EXIDX_CMD_REG_POP
- /* pop register under mask {r3,r2,r1,r0} */
- vsp = ucb->vrs[13];
- mask = UnwTabGetNextInstruction(cb, ucb);
-
- reg = 0;
- while (mask) {
- if ((mask & 1) != 0) {
- uint32_t v;
- if (!cb->readW(vsp,&v))
- return UNWIND_DREAD_W_FAIL;
-
- ucb->vrs[reg] = v;
- vsp += 4;
- }
- mask >>= 1;
- ++reg;
- }
- ucb->vrs[13] = (uint32_t)vsp;
-
- } else
- if (instruction == 0xB2) { // ARM_EXIDX_CMD_DATA_POP
- /* vps = vsp + 0x204 + (uleb128 << 2) */
- ucb->vrs[13] += 0x204 + (UnwTabGetNextInstruction(cb, ucb) << 2);
-
- } else
- if (instruction == 0xB3 || // ARM_EXIDX_CMD_VFP_POP
- instruction == 0xC8 ||
- instruction == 0xC9) {
-
- /* pop VFP double-precision registers */
- vsp = ucb->vrs[13];
-
- /* D[ssss]-D[ssss+cccc] */
- uint32_t v;
- if (!cb->readW(vsp,&v))
- return UNWIND_DREAD_W_FAIL;
-
- ucb->vrs[14] = v;
- vsp += 4;
-
- if (instruction == 0xC8) {
- /* D[16+sssss]-D[16+ssss+cccc] */
- ucb->vrs[14] |= 1 << 16;
- }
-
- if (instruction != 0xB3) {
- /* D[sssss]-D[ssss+cccc] */
- ucb->vrs[14] |= 1 << 17;
- }
-
- ucb->vrs[13] = vsp;
-
- } else
- if ((instruction & 0xF8) == 0xB8 ||
- (instruction & 0xF8) == 0xD0) {
-
- /* Pop VFP double precision registers D[8]-D[8+nnn] */
- ucb->vrs[14] = 0x80 | (instruction & 0x07);
-
- if ((instruction & 0xF8) == 0xD0) {
- ucb->vrs[14] = 1 << 17;
- }
-
- } else
- return UNWIND_UNSUPPORTED_DWARF_INSTR;
- }
-
- return UNWIND_SUCCESS;
- }
-
- static inline __attribute__((always_inline)) uint32_t read_psp() {
-
- /* Read the current PSP and return its value as a pointer */
- uint32_t psp;
-
- __asm__ volatile (
- " mrs %0, psp \n"
- : "=r" (psp) : :
- );
-
- return psp;
- }
-
- /*
- * Unwind the specified frame and goto the previous one
- */
- static UnwResult UnwTabUnwindFrame(const UnwindCallbacks *cb, UnwindFrame *frame) {
-
- UnwResult err;
- UnwTabState ucb;
- const UnwTabEntry *index;
- uint32_t instructions;
-
- /* Search the unwind index for the matching unwind table */
- index = UnwTabSearchIndex(__exidx_start, __exidx_end, frame->pc);
-
- /* Make sure we can unwind this frame */
- if (index->insn == 0x00000001)
- return UNWIND_SUCCESS;
-
- /* Get the pointer to the first unwind instruction */
- if (index->insn & 0x80000000)
- instructions = (uint32_t)&index->insn;
- else
- instructions = prel31_to_addr(&index->insn);
-
- /* Initialize the unwind control block */
- if ((err = UnwTabStateInit(cb, &ucb, instructions, frame)) < 0)
- return err;
-
- /* Execute the unwind instructions */
- err = UnwTabExecuteInstructions(cb, &ucb);
- if (err < 0)
- return err;
-
- /* Set the virtual pc to the virtual lr if this is the first unwind */
- if (ucb.vrs[15] == 0)
- ucb.vrs[15] = ucb.vrs[14];
-
- /* Check for exception return */
- /* TODO Test with other ARM processors to verify this method. */
- if ((ucb.vrs[15] & 0xF0000000) == 0xF0000000) {
- /* According to the Cortex Programming Manual (p.44), the stack address is always 8-byte aligned (Cortex-M7).
- Depending on where the exception came from (MSP or PSP), we need the right SP value to work with.
-
- ucb.vrs[7] contains the right value, so take it and align it by 8 bytes, store it as the current
- SP to work with (ucb.vrs[13]) which is then saved as the current (virtual) frame's SP.
- */
- uint32_t stack;
- ucb.vrs[13] = (ucb.vrs[7] & ~7);
-
- /* If we need to start from the MSP, we need to go down X words to find the PC, where:
- X=2 if it was a non-floating-point exception
- X=20 if it was a floating-point (VFP) exception
-
- If we need to start from the PSP, we need to go up exactly 6 words to find the PC.
- See the ARMv7-M Architecture Reference Manual p.594 and Cortex-M7 Processor Programming Manual p.44/p.45 for details.
- */
- if ((ucb.vrs[15] & 0xC) == 0) {
- /* Return to Handler Mode: MSP (0xFFFFFF-1) */
- stack = ucb.vrs[13];
-
- /* The PC is always 2 words down from the MSP, if it was a non-floating-point exception */
- stack -= 2*4;
-
- /* If there was a VFP exception (0xFFFFFFE1), the PC is located another 18 words down */
- if ((ucb.vrs[15] & 0xF0) == 0xE0) {
- stack -= 18*4;
- }
- }
- else {
- /* Return to Thread Mode: PSP (0xFFFFFF-d) */
- stack = read_psp();
-
- /* The PC is always 6 words up from the PSP */
- stack += 6*4;
- }
-
- /* Store the PC */
- uint32_t v;
- if (!cb->readW(stack,&v))
- return UNWIND_DREAD_W_FAIL;
- ucb.vrs[15] = v;
- stack -= 4;
-
- /* Store the LR */
- if (!cb->readW(stack,&v))
- return UNWIND_DREAD_W_FAIL;
- ucb.vrs[14] = v;
- stack -= 4;
- }
-
- /* We are done if current frame pc is equal to the virtual pc, prevent infinite loop */
- if (frame->pc == ucb.vrs[15])
- return UNWIND_SUCCESS;
-
- /* Update the frame */
- frame->fp = ucb.vrs[7];
- frame->sp = ucb.vrs[13];
- frame->lr = ucb.vrs[14];
- frame->pc = ucb.vrs[15];
-
- /* All good - Continue unwinding */
- return UNWIND_MORE_AVAILABLE;
- }
-
- UnwResult UnwindByTableStart(UnwindFrame* frame, const UnwindCallbacks *cb, void *data) {
-
- UnwResult err = UNWIND_SUCCESS;
- UnwReport entry;
-
- /* Use DWARF unwind information to unwind frames */
- do {
- if (frame->pc == 0) {
- /* Reached __exidx_end. */
- break;
- }
-
- if (frame->pc == 0x00000001) {
- /* Reached .cantunwind instruction. */
- break;
- }
-
- /* Find the unwind index of the current frame pc */
- const UnwTabEntry *index = UnwTabSearchIndex(__exidx_start, __exidx_end, frame->pc);
-
- /* Clear last bit (Thumb indicator) */
- frame->pc &= 0xFFFFFFFEU;
-
- /* Generate the backtrace information */
- entry.address = frame->pc;
- entry.function = prel31_to_addr(&index->addr_offset);
- entry.name = UnwTabGetFunctionName(cb, entry.function);
- if (!cb->report(data,&entry))
- break;
-
- /* Unwind frame and repeat */
- } while ((err = UnwTabUnwindFrame(cb, frame)) == UNWIND_MORE_AVAILABLE);
-
- /* All done */
- return err;
- }
-
- #endif // __arm__ || __thumb__
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