Author: andrew
Date: Thu Jan 17 09:47:56 2013
New Revision: 245549
URL: http://svnweb.freebsd.org/changeset/base/245549
Log:
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.
Modified:
head/sys/arm/arm/db_trace.c
Modified: head/sys/arm/arm/db_trace.c
==============================================================================
--- head/sys/arm/arm/db_trace.c Thu Jan 17 09:37:42 2013 (r245548)
+++ head/sys/arm/arm/db_trace.c Thu Jan 17 09:47:56 2013 (r245549)
@@ -50,6 +50,395 @@ __FBSDID("$FreeBSD$");
#include <ddb/db_sym.h>
#include <ddb/db_output.h>
+#ifdef __ARM_EABI__
+/*
+ * Definitions for the instruction interpreter.
+ *
+ * The ARM EABI specifies how to perform the frame unwinding in the
+ * Exception Handling ABI for the ARM Architecture document. To perform
+ * the unwind we need to know the initial frame pointer, stack pointer,
+ * link register and program counter. We then find the entry within the
+ * index table that points to the function the program counter is within.
+ * This gives us either a list of three instructions to process, a 31-bit
+ * relative offset to a table of instructions, or a value telling us
+ * we can't unwind any further.
+ *
+ * When we have the instructions to process we need to decode them
+ * following table 4 in section 9.3. This describes a collection of bit
+ * patterns to encode that steps to take to update the stack pointer and
+ * link register to the correct values at the start of the function.
+ */
+
+/* A special case when we are unable to unwind past this function */
+#define EXIDX_CANTUNWIND 1
+
+/* The register names */
+#define FP 11
+#define SP 13
+#define LR 14
+#define PC 15
+
+/*
+ * These are set in the linker script. Their addresses will be
+ * either the start or end of the exception table or index.
+ */
+extern int extab_start, extab_end, exidx_start, exidx_end;
+
+/*
+ * Entry types.
+ * These are the only entry types that have been seen in the kernel.
+ */
+#define ENTRY_MASK 0xff000000
+#define ENTRY_ARM_SU16 0x80000000
+#define ENTRY_ARM_LU16 0x81000000
+
+/* Instruction masks. */
+#define INSN_VSP_MASK 0xc0
+#define INSN_VSP_SIZE_MASK 0x3f
+#define INSN_STD_MASK 0xf0
+#define INSN_STD_DATA_MASK 0x0f
+#define INSN_POP_TYPE_MASK 0x08
+#define INSN_POP_COUNT_MASK 0x07
+#define INSN_VSP_LARGE_INC_MASK 0xff
+
+/* Instruction definitions */
+#define INSN_VSP_INC 0x00
+#define INSN_VSP_DEC 0x40
+#define INSN_POP_MASKED 0x80
+#define INSN_VSP_REG 0x90
+#define INSN_POP_COUNT 0xa0
+#define INSN_FINISH 0xb0
+#define INSN_VSP_LARGE_INC 0xb2
+
+/* An item in the exception index table */
+struct unwind_idx {
+ uint32_t offset;
+ uint32_t insn;
+};
+
+/* The state of the unwind process */
+struct unwind_state {
+ uint32_t registers[16];
+ uint32_t start_pc;
+ uint32_t *insn;
+ u_int entries;
+ u_int byte;
+ uint16_t update_mask;
+};
+
+/* We need to provide these but never use them */
+void __aeabi_unwind_cpp_pr0(void);
+void __aeabi_unwind_cpp_pr1(void);
+void __aeabi_unwind_cpp_pr2(void);
+
+void
+__aeabi_unwind_cpp_pr0(void)
+{
+ panic("__aeabi_unwind_cpp_pr0");
+}
+
+void
+__aeabi_unwind_cpp_pr1(void)
+{
+ panic("__aeabi_unwind_cpp_pr1");
+}
+
+void
+__aeabi_unwind_cpp_pr2(void)
+{
+ panic("__aeabi_unwind_cpp_pr2");
+}
+
+/* Expand a 31-bit signed value to a 32-bit signed value */
+static __inline int32_t
+db_expand_prel31(uint32_t prel31)
+{
+
+ return ((int32_t)(prel31 & 0x7fffffffu) << 1) / 2;
+}
+
+/*
+ * Perform a binary search of the index table to find the function
+ * with the largest address that doesn't exceed addr.
+ */
+static struct unwind_idx *
+db_find_index(uint32_t addr)
+{
+ unsigned int min, mid, max;
+ struct unwind_idx *start;
+ struct unwind_idx *item;
+ int32_t prel31_addr;
+ uint32_t func_addr;
+
+ start = (struct unwind_idx *)&exidx_start;
+
+ min = 0;
+ max = (&exidx_end - &exidx_start) / 2;
+
+ while (min != max) {
+ mid = min + (max - min + 1) / 2;
+
+ item = &start[mid];
+
+ prel31_addr = db_expand_prel31(item->offset);
+ func_addr = (uint32_t)&item->offset + prel31_addr;
+
+ if (func_addr <= addr) {
+ min = mid;
+ } else {
+ max = mid - 1;
+ }
+ }
+
+ return &start[min];
+}
+
+/* Reads the next byte from the instruction list */
+static uint8_t
+db_unwind_exec_read_byte(struct unwind_state *state)
+{
+ uint8_t insn;
+
+ /* Read the unwind instruction */
+ insn = (*state->insn) >> (state->byte * 8);
+
+ /* Update the location of the next instruction */
+ if (state->byte == 0) {
+ state->byte = 3;
+ state->insn++;
+ state->entries--;
+ } else
+ state->byte--;
+
+ return insn;
+}
+
+/* Executes the next instruction on the list */
+static int
+db_unwind_exec_insn(struct unwind_state *state)
+{
+ unsigned int insn;
+ uint32_t *vsp = (uint32_t *)state->registers[SP];
+ int update_vsp = 0;
+
+ /* This should never happen */
+ if (state->entries == 0)
+ return 1;
+
+ /* Read the next instruction */
+ insn = db_unwind_exec_read_byte(state);
+
+ if ((insn & INSN_VSP_MASK) == INSN_VSP_INC) {
+ state->registers[SP] += ((insn & INSN_VSP_SIZE_MASK) << 2) + 4;
+
+ } else if ((insn & INSN_VSP_MASK) == INSN_VSP_DEC) {
+ state->registers[SP] -= ((insn & INSN_VSP_SIZE_MASK) << 2) + 4;
+
+ } else if ((insn & INSN_STD_MASK) == INSN_POP_MASKED) {
+ unsigned int mask, reg;
+
+ /* Load the mask */
+ mask = db_unwind_exec_read_byte(state);
+ mask |= (insn & INSN_STD_DATA_MASK) << 8;
+
+ /* We have a refuse to unwind instruction */
+ if (mask == 0)
+ return 1;
+
+ /* Update SP */
+ update_vsp = 1;
+
+ /* Load the registers */
+ for (reg = 4; mask && reg < 16; mask >>= 1, reg++) {
+ if (mask & 1) {
+ state->registers[reg] = *vsp++;
+ state->update_mask |= 1 << reg;
+
+ /* If we have updated SP kep its value */
+ if (reg == SP)
+ update_vsp = 0;
+ }
+ }
+
+ } else if ((insn & INSN_STD_MASK) == INSN_VSP_REG &&
+ ((insn & INSN_STD_DATA_MASK) != 13) &&
+ ((insn & INSN_STD_DATA_MASK) != 15)) {
+ /* sp = register */
+ state->registers[SP] =
+ state->registers[insn & INSN_STD_DATA_MASK];
+
+ } else if ((insn & INSN_STD_MASK) == INSN_POP_COUNT) {
+ unsigned int count, reg;
+
+ /* Read how many registers to load */
+ count = insn & INSN_POP_COUNT_MASK;
+
+ /* Update sp */
+ update_vsp = 1;
+
+ /* Pop the registers */
+ for (reg = 4; reg <= 4 + count; reg++) {
+ state->registers[reg] = *vsp++;
+ state->update_mask |= 1 << reg;
+ }
+
+ /* Check if we are in the pop r14 version */
+ if ((insn & INSN_POP_TYPE_MASK) != 0) {
+ state->registers[14] = *vsp++;
+ }
+
+ } else if (insn == INSN_FINISH) {
+ /* Stop processing */
+ state->entries = 0;
+
+ } else if ((insn & INSN_VSP_LARGE_INC_MASK) == INSN_VSP_LARGE_INC) {
+ unsigned int uleb128;
+
+ /* Read the increment value */
+ uleb128 = db_unwind_exec_read_byte(state);
+
+ state->registers[SP] += 0x204 + (uleb128 << 2);
+
+ } else {
+ /* We hit a new instruction that needs to be implemented */
+ db_printf("Unhandled instruction %.2x\n", insn);
+ return 1;
+ }
+
+ if (update_vsp) {
+ state->registers[SP] = (uint32_t)vsp;
+ }
+
+#if 0
+ db_printf("fp = %08x, sp = %08x, lr = %08x, pc = %08x\n",
+ state->registers[FP], state->registers[SP], state->registers[LR],
+ state->registers[PC]);
+#endif
+
+ return 0;
+}
+
+/* Performs the unwind of a function */
+static int
+db_unwind_tab(struct unwind_state *state)
+{
+ uint32_t entry;
+
+ /* Set PC to a known value */
+ state->registers[PC] = 0;
+
+ /* Read the personality */
+ entry = *state->insn & ENTRY_MASK;
+
+ if (entry == ENTRY_ARM_SU16) {
+ state->byte = 2;
+ state->entries = 1;
+ } else if (entry == ENTRY_ARM_LU16) {
+ state->byte = 1;
+ state->entries = ((*state->insn >> 16) & 0xFF) + 1;
+ } else {
+ db_printf("Unknown entry: %x\n", entry);
+ return 1;
+ }
+
+ while (state->entries > 0) {
+ if (db_unwind_exec_insn(state) != 0)
+ return 1;
+ }
+
+ /*
+ * The program counter was not updated, load it from the link register.
+ */
+ if (state->registers[PC] == 0)
+ state->registers[PC] = state->registers[LR];
+
+ return 0;
+}
+
+static void
+db_stack_trace_cmd(struct unwind_state *state)
+{
+ struct unwind_idx *index;
+ const char *name;
+ db_expr_t value;
+ db_expr_t offset;
+ c_db_sym_t sym;
+ u_int reg, i;
+ char *sep;
+
+ while (1) {
+ /* Reset the mask of updated registers */
+ state->update_mask = 0;
+
+ /* The pc value is correct and will be overwritten, save it */
+ state->start_pc = state->registers[PC];
+
+ /* Find the item to run */
+ index = db_find_index(state->start_pc);
+
+ if (index->insn == EXIDX_CANTUNWIND) {
+ printf("Unable to unwind\n");
+ break;
+ } else if (index->insn & (1 << 31)) {
+ /* The data is within the instruction */
+ state->insn = &index->insn;
+ } else {
+ /* We have a prel31 offset to the unwind table */
+ uint32_t prel31_tbl = db_expand_prel31(index->insn);
+
+ state->insn = (uint32_t *)((uintptr_t)&index->insn +
+ prel31_tbl);
+ }
+
+ /* Run the unwind function */
+ if (db_unwind_tab(state) != 0)
+ break;
+
+ /* This is not a kernel address, stop processing */
+ if (state->registers[PC] < VM_MIN_KERNEL_ADDRESS)
+ break;
+
+ /* Print the frame details */
+ sym = db_search_symbol(state->start_pc, DB_STGY_ANY, &offset);
+ if (sym == C_DB_SYM_NULL) {
+ value = 0;
+ name = "(null)";
+ } else
+ db_symbol_values(sym, &name, &value);
+ db_printf("%s() at ", name);
+ db_printsym(state->start_pc, DB_STGY_PROC);
+ db_printf("\n");
+ db_printf("\t pc = 0x%08x lr = 0x%08x (", state->start_pc,
+ state->registers[LR]);
+ db_printsym(state->registers[LR], DB_STGY_PROC);
+ db_printf(")\n");
+ db_printf("\t sp = 0x%08x fp = 0x%08x",
+ state->registers[SP], state->registers[FP]);
+
+ /* Don't print the registers we have already printed */
+ state->update_mask &= ~((1 << SP) | (1 << FP) | (1 << LR) |
+ (1 << PC));
+ sep = "\n\t";
+ for (i = 0, reg = 0; state->update_mask != 0;
+ state->update_mask >>= 1, reg++) {
+ if ((state->update_mask & 1) != 0) {
+ db_printf("%s%sr%d = 0x%08x", sep,
+ (reg < 10) ? " " : "", reg,
+ state->registers[reg]);
+ i++;
+ if (i == 2) {
+ sep = "\n\t";
+ i = 0;
+ } else
+ sep = " ";
+
+ }
+ }
+ db_printf("\n");
+ }
+}
+#endif
+
/*
* APCS stack frames are awkward beasts, so I don't think even trying to use
* a structure to represent them is a good idea.
@@ -78,6 +467,7 @@ __FBSDID("$FreeBSD$");
* fields are actually present.
*/
+#ifndef __ARM_EABI__ /* The frame format is differend in AAPCS */
static void
db_stack_trace_cmd(db_expr_t addr, db_expr_t count, boolean_t kernel_only)
{
@@ -171,6 +561,7 @@ db_stack_trace_cmd(db_expr_t addr, db_ex
}
}
}
+#endif
/* XXX stubs */
void
@@ -193,11 +584,24 @@ db_md_set_watchpoint(db_expr_t addr, db_
int
db_trace_thread(struct thread *thr, int count)
{
+#ifdef __ARM_EABI__
+ struct unwind_state state;
+#endif
struct pcb *ctx;
if (thr != curthread) {
ctx = kdb_thr_ctx(thr);
+
+#ifdef __ARM_EABI__
+ state.registers[FP] = ctx->un_32.pcb32_r11;
+ state.registers[SP] = ctx->un_32.pcb32_sp;
+ state.registers[LR] = ctx->un_32.pcb32_lr;
+ state.registers[PC] = ctx->un_32.pcb32_pc;
+
+ db_stack_trace_cmd(&state);
+#else
db_stack_trace_cmd(ctx->un_32.pcb32_r11, -1, TRUE);
+#endif
} else
db_trace_self();
return (0);
@@ -206,8 +610,20 @@ db_trace_thread(struct thread *thr, int
void
db_trace_self(void)
{
+#ifdef __ARM_EABI__
+ struct unwind_state state;
+ register uint32_t sp __asm__ ("sp");
+
+ state.registers[FP] = (uint32_t)__builtin_frame_address(0);
+ state.registers[SP] = (uint32_t)sp;
+ state.registers[LR] = (uint32_t)__builtin_return_address(0);
+ state.registers[PC] = (uint32_t)db_trace_self;
+
+ db_stack_trace_cmd(&state);
+#else
db_addr_t addr;
addr = (db_addr_t)__builtin_frame_address(0);
db_stack_trace_cmd(addr, -1, FALSE);
+#endif
}
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