Implement stack unwinding based on section 9 of the "Exception handling ABI
for the ARM architecture" documentation. The unwind tables are currently not stored in the kernel but will be added later.
This commit is contained in:
Andrew Turner
parent
46d741dc7f
commit
29ce0a2aff
@ -50,6 +50,395 @@ __FBSDID("$FreeBSD$");
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#include <ddb/db_sym.h>
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#include <ddb/db_output.h>
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#ifdef __ARM_EABI__
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/*
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* Definitions for the instruction interpreter.
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*
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* The ARM EABI specifies how to perform the frame unwinding in the
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* Exception Handling ABI for the ARM Architecture document. To perform
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* the unwind we need to know the initial frame pointer, stack pointer,
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* link register and program counter. We then find the entry within the
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* index table that points to the function the program counter is within.
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* This gives us either a list of three instructions to process, a 31-bit
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* relative offset to a table of instructions, or a value telling us
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* we can't unwind any further.
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*
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* When we have the instructions to process we need to decode them
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* following table 4 in section 9.3. This describes a collection of bit
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* patterns to encode that steps to take to update the stack pointer and
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* link register to the correct values at the start of the function.
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*/
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/* A special case when we are unable to unwind past this function */
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#define EXIDX_CANTUNWIND 1
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/* The register names */
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#define FP 11
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#define SP 13
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#define LR 14
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#define PC 15
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/*
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* These are set in the linker script. Their addresses will be
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* either the start or end of the exception table or index.
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*/
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extern int extab_start, extab_end, exidx_start, exidx_end;
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/*
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* Entry types.
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* These are the only entry types that have been seen in the kernel.
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*/
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#define ENTRY_MASK 0xff000000
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#define ENTRY_ARM_SU16 0x80000000
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#define ENTRY_ARM_LU16 0x81000000
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/* Instruction masks. */
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#define INSN_VSP_MASK 0xc0
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#define INSN_VSP_SIZE_MASK 0x3f
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#define INSN_STD_MASK 0xf0
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#define INSN_STD_DATA_MASK 0x0f
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#define INSN_POP_TYPE_MASK 0x08
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#define INSN_POP_COUNT_MASK 0x07
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#define INSN_VSP_LARGE_INC_MASK 0xff
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/* Instruction definitions */
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#define INSN_VSP_INC 0x00
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#define INSN_VSP_DEC 0x40
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#define INSN_POP_MASKED 0x80
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#define INSN_VSP_REG 0x90
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#define INSN_POP_COUNT 0xa0
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#define INSN_FINISH 0xb0
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#define INSN_VSP_LARGE_INC 0xb2
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/* An item in the exception index table */
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struct unwind_idx {
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uint32_t offset;
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uint32_t insn;
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};
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/* The state of the unwind process */
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struct unwind_state {
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uint32_t registers[16];
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uint32_t start_pc;
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uint32_t *insn;
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u_int entries;
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u_int byte;
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uint16_t update_mask;
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};
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/* We need to provide these but never use them */
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void __aeabi_unwind_cpp_pr0(void);
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void __aeabi_unwind_cpp_pr1(void);
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void __aeabi_unwind_cpp_pr2(void);
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void
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__aeabi_unwind_cpp_pr0(void)
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{
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panic("__aeabi_unwind_cpp_pr0");
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}
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void
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__aeabi_unwind_cpp_pr1(void)
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{
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panic("__aeabi_unwind_cpp_pr1");
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}
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void
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__aeabi_unwind_cpp_pr2(void)
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{
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panic("__aeabi_unwind_cpp_pr2");
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}
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/* Expand a 31-bit signed value to a 32-bit signed value */
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static __inline int32_t
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db_expand_prel31(uint32_t prel31)
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{
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return ((int32_t)(prel31 & 0x7fffffffu) << 1) / 2;
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}
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/*
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* Perform a binary search of the index table to find the function
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* with the largest address that doesn't exceed addr.
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*/
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static struct unwind_idx *
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db_find_index(uint32_t addr)
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{
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unsigned int min, mid, max;
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struct unwind_idx *start;
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struct unwind_idx *item;
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int32_t prel31_addr;
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uint32_t func_addr;
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start = (struct unwind_idx *)&exidx_start;
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min = 0;
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max = (&exidx_end - &exidx_start) / 2;
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while (min != max) {
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mid = min + (max - min + 1) / 2;
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item = &start[mid];
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prel31_addr = db_expand_prel31(item->offset);
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func_addr = (uint32_t)&item->offset + prel31_addr;
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if (func_addr <= addr) {
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min = mid;
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} else {
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max = mid - 1;
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}
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}
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return &start[min];
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}
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/* Reads the next byte from the instruction list */
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static uint8_t
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db_unwind_exec_read_byte(struct unwind_state *state)
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{
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uint8_t insn;
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/* Read the unwind instruction */
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insn = (*state->insn) >> (state->byte * 8);
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/* Update the location of the next instruction */
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if (state->byte == 0) {
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state->byte = 3;
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state->insn++;
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state->entries--;
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} else
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state->byte--;
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return insn;
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}
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/* Executes the next instruction on the list */
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static int
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db_unwind_exec_insn(struct unwind_state *state)
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{
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unsigned int insn;
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uint32_t *vsp = (uint32_t *)state->registers[SP];
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int update_vsp = 0;
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/* This should never happen */
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if (state->entries == 0)
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return 1;
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/* Read the next instruction */
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insn = db_unwind_exec_read_byte(state);
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if ((insn & INSN_VSP_MASK) == INSN_VSP_INC) {
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state->registers[SP] += ((insn & INSN_VSP_SIZE_MASK) << 2) + 4;
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} else if ((insn & INSN_VSP_MASK) == INSN_VSP_DEC) {
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state->registers[SP] -= ((insn & INSN_VSP_SIZE_MASK) << 2) + 4;
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} else if ((insn & INSN_STD_MASK) == INSN_POP_MASKED) {
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unsigned int mask, reg;
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/* Load the mask */
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mask = db_unwind_exec_read_byte(state);
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mask |= (insn & INSN_STD_DATA_MASK) << 8;
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/* We have a refuse to unwind instruction */
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if (mask == 0)
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return 1;
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/* Update SP */
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update_vsp = 1;
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/* Load the registers */
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for (reg = 4; mask && reg < 16; mask >>= 1, reg++) {
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if (mask & 1) {
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state->registers[reg] = *vsp++;
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state->update_mask |= 1 << reg;
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/* If we have updated SP kep its value */
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if (reg == SP)
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update_vsp = 0;
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}
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}
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} else if ((insn & INSN_STD_MASK) == INSN_VSP_REG &&
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((insn & INSN_STD_DATA_MASK) != 13) &&
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((insn & INSN_STD_DATA_MASK) != 15)) {
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/* sp = register */
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state->registers[SP] =
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state->registers[insn & INSN_STD_DATA_MASK];
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} else if ((insn & INSN_STD_MASK) == INSN_POP_COUNT) {
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unsigned int count, reg;
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/* Read how many registers to load */
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count = insn & INSN_POP_COUNT_MASK;
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/* Update sp */
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update_vsp = 1;
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/* Pop the registers */
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for (reg = 4; reg <= 4 + count; reg++) {
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state->registers[reg] = *vsp++;
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state->update_mask |= 1 << reg;
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}
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/* Check if we are in the pop r14 version */
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if ((insn & INSN_POP_TYPE_MASK) != 0) {
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state->registers[14] = *vsp++;
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}
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} else if (insn == INSN_FINISH) {
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/* Stop processing */
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state->entries = 0;
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} else if ((insn & INSN_VSP_LARGE_INC_MASK) == INSN_VSP_LARGE_INC) {
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unsigned int uleb128;
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/* Read the increment value */
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uleb128 = db_unwind_exec_read_byte(state);
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state->registers[SP] += 0x204 + (uleb128 << 2);
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} else {
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/* We hit a new instruction that needs to be implemented */
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db_printf("Unhandled instruction %.2x\n", insn);
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return 1;
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}
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if (update_vsp) {
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state->registers[SP] = (uint32_t)vsp;
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}
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#if 0
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db_printf("fp = %08x, sp = %08x, lr = %08x, pc = %08x\n",
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state->registers[FP], state->registers[SP], state->registers[LR],
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state->registers[PC]);
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#endif
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return 0;
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}
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/* Performs the unwind of a function */
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static int
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db_unwind_tab(struct unwind_state *state)
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{
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uint32_t entry;
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/* Set PC to a known value */
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state->registers[PC] = 0;
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/* Read the personality */
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entry = *state->insn & ENTRY_MASK;
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if (entry == ENTRY_ARM_SU16) {
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state->byte = 2;
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state->entries = 1;
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} else if (entry == ENTRY_ARM_LU16) {
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state->byte = 1;
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state->entries = ((*state->insn >> 16) & 0xFF) + 1;
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} else {
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db_printf("Unknown entry: %x\n", entry);
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return 1;
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}
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while (state->entries > 0) {
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if (db_unwind_exec_insn(state) != 0)
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return 1;
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}
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/*
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* The program counter was not updated, load it from the link register.
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*/
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if (state->registers[PC] == 0)
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state->registers[PC] = state->registers[LR];
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return 0;
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}
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static void
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db_stack_trace_cmd(struct unwind_state *state)
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{
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struct unwind_idx *index;
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const char *name;
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db_expr_t value;
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db_expr_t offset;
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c_db_sym_t sym;
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u_int reg, i;
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char *sep;
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while (1) {
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/* Reset the mask of updated registers */
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state->update_mask = 0;
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/* The pc value is correct and will be overwritten, save it */
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state->start_pc = state->registers[PC];
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/* Find the item to run */
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index = db_find_index(state->start_pc);
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if (index->insn == EXIDX_CANTUNWIND) {
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printf("Unable to unwind\n");
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break;
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} else if (index->insn & (1 << 31)) {
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/* The data is within the instruction */
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state->insn = &index->insn;
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} else {
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/* We have a prel31 offset to the unwind table */
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uint32_t prel31_tbl = db_expand_prel31(index->insn);
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state->insn = (uint32_t *)((uintptr_t)&index->insn +
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prel31_tbl);
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}
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/* Run the unwind function */
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if (db_unwind_tab(state) != 0)
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break;
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/* This is not a kernel address, stop processing */
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if (state->registers[PC] < VM_MIN_KERNEL_ADDRESS)
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break;
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/* Print the frame details */
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sym = db_search_symbol(state->start_pc, DB_STGY_ANY, &offset);
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if (sym == C_DB_SYM_NULL) {
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value = 0;
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name = "(null)";
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} else
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db_symbol_values(sym, &name, &value);
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db_printf("%s() at ", name);
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db_printsym(state->start_pc, DB_STGY_PROC);
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db_printf("\n");
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db_printf("\t pc = 0x%08x lr = 0x%08x (", state->start_pc,
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state->registers[LR]);
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db_printsym(state->registers[LR], DB_STGY_PROC);
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db_printf(")\n");
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db_printf("\t sp = 0x%08x fp = 0x%08x",
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state->registers[SP], state->registers[FP]);
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/* Don't print the registers we have already printed */
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state->update_mask &= ~((1 << SP) | (1 << FP) | (1 << LR) |
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(1 << PC));
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sep = "\n\t";
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for (i = 0, reg = 0; state->update_mask != 0;
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state->update_mask >>= 1, reg++) {
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if ((state->update_mask & 1) != 0) {
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db_printf("%s%sr%d = 0x%08x", sep,
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(reg < 10) ? " " : "", reg,
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state->registers[reg]);
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i++;
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if (i == 2) {
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sep = "\n\t";
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i = 0;
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} else
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sep = " ";
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}
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}
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db_printf("\n");
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}
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}
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#endif
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/*
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* APCS stack frames are awkward beasts, so I don't think even trying to use
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* a structure to represent them is a good idea.
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@ -78,6 +467,7 @@ __FBSDID("$FreeBSD$");
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* fields are actually present.
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*/
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#ifndef __ARM_EABI__ /* The frame format is differend in AAPCS */
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static void
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db_stack_trace_cmd(db_expr_t addr, db_expr_t count, boolean_t kernel_only)
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{
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@ -171,6 +561,7 @@ db_stack_trace_cmd(db_expr_t addr, db_expr_t count, boolean_t kernel_only)
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}
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}
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}
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#endif
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/* XXX stubs */
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void
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@ -193,11 +584,24 @@ db_md_set_watchpoint(db_expr_t addr, db_expr_t size)
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int
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db_trace_thread(struct thread *thr, int count)
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{
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#ifdef __ARM_EABI__
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struct unwind_state state;
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#endif
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struct pcb *ctx;
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if (thr != curthread) {
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ctx = kdb_thr_ctx(thr);
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#ifdef __ARM_EABI__
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state.registers[FP] = ctx->un_32.pcb32_r11;
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state.registers[SP] = ctx->un_32.pcb32_sp;
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state.registers[LR] = ctx->un_32.pcb32_lr;
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state.registers[PC] = ctx->un_32.pcb32_pc;
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db_stack_trace_cmd(&state);
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#else
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db_stack_trace_cmd(ctx->un_32.pcb32_r11, -1, TRUE);
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#endif
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} else
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db_trace_self();
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return (0);
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@ -206,8 +610,20 @@ db_trace_thread(struct thread *thr, int count)
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void
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db_trace_self(void)
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{
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#ifdef __ARM_EABI__
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struct unwind_state state;
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register uint32_t sp __asm__ ("sp");
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state.registers[FP] = (uint32_t)__builtin_frame_address(0);
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state.registers[SP] = (uint32_t)sp;
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state.registers[LR] = (uint32_t)__builtin_return_address(0);
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state.registers[PC] = (uint32_t)db_trace_self;
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db_stack_trace_cmd(&state);
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#else
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db_addr_t addr;
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addr = (db_addr_t)__builtin_frame_address(0);
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db_stack_trace_cmd(addr, -1, FALSE);
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#endif
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}
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