1 files changed, 420 insertions, 0 deletions
diff --git a/sys/arm/arm/unwind.c b/sys/arm/arm/unwind.c
new file mode 100644
index 000000000000..25fd20003ecf
--- /dev/null
+++ b/sys/arm/arm/unwind.c
@@ -0,0 +1,420 @@
+/*
+ * Copyright 2013-2014 Andrew Turner.
+ * Copyright 2013-2014 Ian Lepore.
+ * Copyright 2013-2014 Rui Paulo.
+ * Copyright 2013 Eitan Adler.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *  1. Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *  2. Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/linker.h>
+
+#include <machine/stack.h>
+
+#include "linker_if.h"
+
+/*
+ * 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
+
+/*
+ * These are set in the linker script. Their addresses will be
+ * either the start or end of the exception table or index.
+ */
+extern int 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_POP_REGS		0xb1
+#define	INSN_VSP_LARGE_INC	0xb2
+
+/* An item in the exception index table */
+struct unwind_idx {
+	uint32_t offset;
+	uint32_t insn;
+};
+
+/* Expand a 31-bit signed value to a 32-bit signed value */
+static __inline int32_t
+expand_prel31(uint32_t prel31)
+{
+
+	return ((int32_t)(prel31 & 0x7fffffffu) << 1) / 2;
+}
+
+struct search_context {
+	uint32_t addr;
+	caddr_t exidx_start;
+	caddr_t exidx_end;
+};
+
+static int
+module_search(linker_file_t lf, void *context)
+{
+	struct search_context *sc = context;
+	linker_symval_t symval;
+	c_linker_sym_t sym;
+
+	if (lf->address <= (caddr_t)sc->addr &&
+	    (lf->address + lf->size) >= (caddr_t)sc->addr) {
+		if ((LINKER_LOOKUP_SYMBOL(lf, "__exidx_start", &sym) == 0 ||
+		    LINKER_LOOKUP_SYMBOL(lf, "exidx_start", &sym) == 0) &&
+		    LINKER_SYMBOL_VALUES(lf, sym, &symval) == 0)
+			sc->exidx_start = symval.value;
+
+		if ((LINKER_LOOKUP_SYMBOL(lf, "__exidx_end", &sym) == 0 ||
+		    LINKER_LOOKUP_SYMBOL(lf, "exidx_end", &sym) == 0) &&
+		    LINKER_SYMBOL_VALUES(lf, sym, &symval) == 0)
+			sc->exidx_end = symval.value;
+
+		if (sc->exidx_start != NULL && sc->exidx_end != NULL)
+			return (1);
+		panic("Invalid module %s, no unwind tables\n", lf->filename);
+	}
+	return (0);
+}
+
+/*
+ * 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 *
+find_index(uint32_t addr, int search_modules)
+{
+	struct search_context sc;
+	caddr_t idx_start, idx_end;
+	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;
+	idx_start = (caddr_t)&exidx_start;
+	idx_end = (caddr_t)&exidx_end;
+
+	/* This may acquire a lock */
+	if (search_modules) {
+		bzero(&sc, sizeof(sc));
+		sc.addr = addr;
+		if (linker_file_foreach(module_search, &sc) != 0 &&
+		   sc.exidx_start != NULL && sc.exidx_end != NULL) {
+			start = (struct unwind_idx *)sc.exidx_start;
+			idx_start = sc.exidx_start;
+			idx_end = sc.exidx_end;
+		}
+	}
+
+	min = 0;
+	max = (idx_end - idx_start) / sizeof(struct unwind_idx);
+
+	while (min != max) {
+		mid = min + (max - min + 1) / 2;
+
+		item = &start[mid];
+
+		prel31_addr = 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
+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
+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 = 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 = 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_POP_REGS) {
+		unsigned int mask, reg;
+
+		mask = unwind_exec_read_byte(state);
+		if (mask == 0 || (mask & 0xf0) != 0)
+			return 1;
+
+		/* Update SP */
+		update_vsp = 1;
+
+		/* Load the registers */
+		for (reg = 0; mask && reg < 4; mask >>= 1, reg++) {
+			if (mask & 1) {
+				state->registers[reg] = *vsp++;
+				state->update_mask |= 1 << reg;
+			}
+		}
+
+	} else if ((insn & INSN_VSP_LARGE_INC_MASK) == INSN_VSP_LARGE_INC) {
+		unsigned int uleb128;
+
+		/* Read the increment value */
+		uleb128 = unwind_exec_read_byte(state);
+
+		state->registers[SP] += 0x204 + (uleb128 << 2);
+
+	} else {
+		/* We hit a new instruction that needs to be implemented */
+#if 0
+		db_printf("Unhandled instruction %.2x\n", insn);
+#endif
+		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
+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 {
+#if 0
+		db_printf("Unknown entry: %x\n", entry);
+#endif
+		return 1;
+	}
+
+	while (state->entries > 0) {
+		if (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];
+
+		/*
+		 * If the program counter changed, flag it in the update mask.
+		 */
+		if (state->start_pc != state->registers[PC])
+			state->update_mask |= 1 << PC;
+	}
+
+	return 0;
+}
+
+int
+unwind_stack_one(struct unwind_state *state, int can_lock)
+{
+	struct unwind_idx *index;
+	int finished;
+
+	/* 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 = find_index(state->start_pc, can_lock);
+
+	finished = 0;
+	if (index->insn != EXIDX_CANTUNWIND) {
+		if (index->insn & (1U << 31)) {
+			/* The data is within the instruction */
+			state->insn = &index->insn;
+		} else {
+			/* A prel31 offset to the unwind table */
+			state->insn = (uint32_t *)
+			    ((uintptr_t)&index->insn +
+			     expand_prel31(index->insn));
+		}
+		/* Run the unwind function */
+		finished = unwind_tab(state);
+	}
+
+	/* This is the top of the stack, finish */
+	if (index->insn == EXIDX_CANTUNWIND)
+		finished = 1;
+
+	return (finished);
+}