Current firmware of my FLSUN QQ-S Pro
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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://www.mozilla.org/en-US/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__