1 files changed, 608 insertions, 0 deletions

diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
new file mode 100644
index 0000000000..9d21921560
--- /dev/null
+++ b/arch/arm/kernel/unwind.c
@@ -0,0 +1,608 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * arch/arm/kernel/unwind.c
+ *
+ * Copyright (C) 2008 ARM Limited
+ *
+ * Stack unwinding support for ARM
+ *
+ * An ARM EABI version of gcc is required to generate the unwind
+ * tables. For information about the structure of the unwind tables,
+ * see "Exception Handling ABI for the ARM Architecture" at:
+ *
+ * http://infocenter.arm.com/help/topic/com.arm.doc.subset.swdev.abi/index.html
+ */
+
+#ifndef __CHECKER__
+#if !defined (__ARM_EABI__)
+#warning Your compiler does not have EABI support.
+#warning    ARM unwind is known to compile only with EABI compilers.
+#warning    Change compiler or disable ARM_UNWIND option.
+#endif
+#endif /* __CHECKER__ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/list.h>
+#include <linux/module.h>
+
+#include <asm/stacktrace.h>
+#include <asm/traps.h>
+#include <asm/unwind.h>
+
+#include "reboot.h"
+
+/* Dummy functions to avoid linker complaints */
+void __aeabi_unwind_cpp_pr0(void)
+{
+};
+EXPORT_SYMBOL(__aeabi_unwind_cpp_pr0);
+
+void __aeabi_unwind_cpp_pr1(void)
+{
+};
+EXPORT_SYMBOL(__aeabi_unwind_cpp_pr1);
+
+void __aeabi_unwind_cpp_pr2(void)
+{
+};
+EXPORT_SYMBOL(__aeabi_unwind_cpp_pr2);
+
+struct unwind_ctrl_block {
+	unsigned long vrs[16];		/* virtual register set */
+	const unsigned long *insn;	/* pointer to the current instructions word */
+	unsigned long sp_high;		/* highest value of sp allowed */
+	unsigned long *lr_addr;		/* address of LR value on the stack */
+	/*
+	 * 1 : check for stack overflow for each register pop.
+	 * 0 : save overhead if there is plenty of stack remaining.
+	 */
+	int check_each_pop;
+	int entries;			/* number of entries left to interpret */
+	int byte;			/* current byte number in the instructions word */
+};
+
+enum regs {
+#ifdef CONFIG_THUMB2_KERNEL
+	FP = 7,
+#else
+	FP = 11,
+#endif
+	SP = 13,
+	LR = 14,
+	PC = 15
+};
+
+extern const struct unwind_idx __start_unwind_idx[];
+static const struct unwind_idx *__origin_unwind_idx;
+extern const struct unwind_idx __stop_unwind_idx[];
+
+static DEFINE_RAW_SPINLOCK(unwind_lock);
+static LIST_HEAD(unwind_tables);
+
+/* Convert a prel31 symbol to an absolute address */
+#define prel31_to_addr(ptr)				\
+({							\
+	/* sign-extend to 32 bits */			\
+	long offset = (((long)*(ptr)) << 1) >> 1;	\
+	(unsigned long)(ptr) + offset;			\
+})
+
+/*
+ * Binary search in the unwind index. The entries are
+ * guaranteed to be sorted in ascending order by the linker.
+ *
+ * start = first entry
+ * origin = first entry with positive offset (or stop if there is no such entry)
+ * stop - 1 = last entry
+ */
+static const struct unwind_idx *search_index(unsigned long addr,
+				       const struct unwind_idx *start,
+				       const struct unwind_idx *origin,
+				       const struct unwind_idx *stop)
+{
+	unsigned long addr_prel31;
+
+	pr_debug("%s(%08lx, %p, %p, %p)\n",
+			__func__, addr, start, origin, stop);
+
+	/*
+	 * only search in the section with the matching sign. This way the
+	 * prel31 numbers can be compared as unsigned longs.
+	 */
+	if (addr < (unsigned long)start)
+		/* negative offsets: [start; origin) */
+		stop = origin;
+	else
+		/* positive offsets: [origin; stop) */
+		start = origin;
+
+	/* prel31 for address relavive to start */
+	addr_prel31 = (addr - (unsigned long)start) & 0x7fffffff;
+
+	while (start < stop - 1) {
+		const struct unwind_idx *mid = start + ((stop - start) >> 1);
+
+		/*
+		 * As addr_prel31 is relative to start an offset is needed to
+		 * make it relative to mid.
+		 */
+		if (addr_prel31 - ((unsigned long)mid - (unsigned long)start) <
+				mid->addr_offset)
+			stop = mid;
+		else {
+			/* keep addr_prel31 relative to start */
+			addr_prel31 -= ((unsigned long)mid -
+					(unsigned long)start);
+			start = mid;
+		}
+	}
+
+	if (likely(start->addr_offset <= addr_prel31))
+		return start;
+	else {
+		pr_warn("unwind: Unknown symbol address %08lx\n", addr);
+		return NULL;
+	}
+}
+
+static const struct unwind_idx *unwind_find_origin(
+		const struct unwind_idx *start, const struct unwind_idx *stop)
+{
+	pr_debug("%s(%p, %p)\n", __func__, start, stop);
+	while (start < stop) {
+		const struct unwind_idx *mid = start + ((stop - start) >> 1);
+
+		if (mid->addr_offset >= 0x40000000)
+			/* negative offset */
+			start = mid + 1;
+		else
+			/* positive offset */
+			stop = mid;
+	}
+	pr_debug("%s -> %p\n", __func__, stop);
+	return stop;
+}
+
+static const struct unwind_idx *unwind_find_idx(unsigned long addr)
+{
+	const struct unwind_idx *idx = NULL;
+	unsigned long flags;
+
+	pr_debug("%s(%08lx)\n", __func__, addr);
+
+	if (core_kernel_text(addr)) {
+		if (unlikely(!__origin_unwind_idx))
+			__origin_unwind_idx =
+				unwind_find_origin(__start_unwind_idx,
+						__stop_unwind_idx);
+
+		/* main unwind table */
+		idx = search_index(addr, __start_unwind_idx,
+				   __origin_unwind_idx,
+				   __stop_unwind_idx);
+	} else {
+		/* module unwind tables */
+		struct unwind_table *table;
+
+		raw_spin_lock_irqsave(&unwind_lock, flags);
+		list_for_each_entry(table, &unwind_tables, list) {
+			if (addr >= table->begin_addr &&
+			    addr < table->end_addr) {
+				idx = search_index(addr, table->start,
+						   table->origin,
+						   table->stop);
+				/* Move-to-front to exploit common traces */
+				list_move(&table->list, &unwind_tables);
+				break;
+			}
+		}
+		raw_spin_unlock_irqrestore(&unwind_lock, flags);
+	}
+
+	pr_debug("%s: idx = %p\n", __func__, idx);
+	return idx;
+}
+
+static unsigned long unwind_get_byte(struct unwind_ctrl_block *ctrl)
+{
+	unsigned long ret;
+
+	if (ctrl->entries <= 0) {
+		pr_warn("unwind: Corrupt unwind table\n");
+		return 0;
+	}
+
+	ret = (*ctrl->insn >> (ctrl->byte * 8)) & 0xff;
+
+	if (ctrl->byte == 0) {
+		ctrl->insn++;
+		ctrl->entries--;
+		ctrl->byte = 3;
+	} else
+		ctrl->byte--;
+
+	return ret;
+}
+
+/* Before poping a register check whether it is feasible or not */
+static int unwind_pop_register(struct unwind_ctrl_block *ctrl,
+				unsigned long **vsp, unsigned int reg)
+{
+	if (unlikely(ctrl->check_each_pop))
+		if (*vsp >= (unsigned long *)ctrl->sp_high)
+			return -URC_FAILURE;
+
+	/* Use READ_ONCE_NOCHECK here to avoid this memory access
+	 * from being tracked by KASAN.
+	 */
+	ctrl->vrs[reg] = READ_ONCE_NOCHECK(*(*vsp));
+	if (reg == 14)
+		ctrl->lr_addr = *vsp;
+	(*vsp)++;
+	return URC_OK;
+}
+
+/* Helper functions to execute the instructions */
+static int unwind_exec_pop_subset_r4_to_r13(struct unwind_ctrl_block *ctrl,
+						unsigned long mask)
+{
+	unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
+	int load_sp, reg = 4;
+
+	load_sp = mask & (1 << (13 - 4));
+	while (mask) {
+		if (mask & 1)
+			if (unwind_pop_register(ctrl, &vsp, reg))
+				return -URC_FAILURE;
+		mask >>= 1;
+		reg++;
+	}
+	if (!load_sp) {
+		ctrl->vrs[SP] = (unsigned long)vsp;
+	}
+
+	return URC_OK;
+}
+
+static int unwind_exec_pop_r4_to_rN(struct unwind_ctrl_block *ctrl,
+					unsigned long insn)
+{
+	unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
+	int reg;
+
+	/* pop R4-R[4+bbb] */
+	for (reg = 4; reg <= 4 + (insn & 7); reg++)
+		if (unwind_pop_register(ctrl, &vsp, reg))
+				return -URC_FAILURE;
+
+	if (insn & 0x8)
+		if (unwind_pop_register(ctrl, &vsp, 14))
+				return -URC_FAILURE;
+
+	ctrl->vrs[SP] = (unsigned long)vsp;
+
+	return URC_OK;
+}
+
+static int unwind_exec_pop_subset_r0_to_r3(struct unwind_ctrl_block *ctrl,
+						unsigned long mask)
+{
+	unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
+	int reg = 0;
+
+	/* pop R0-R3 according to mask */
+	while (mask) {
+		if (mask & 1)
+			if (unwind_pop_register(ctrl, &vsp, reg))
+				return -URC_FAILURE;
+		mask >>= 1;
+		reg++;
+	}
+	ctrl->vrs[SP] = (unsigned long)vsp;
+
+	return URC_OK;
+}
+
+static unsigned long unwind_decode_uleb128(struct unwind_ctrl_block *ctrl)
+{
+	unsigned long bytes = 0;
+	unsigned long insn;
+	unsigned long result = 0;
+
+	/*
+	 * unwind_get_byte() will advance `ctrl` one instruction at a time, so
+	 * loop until we get an instruction byte where bit 7 is not set.
+	 *
+	 * Note: This decodes a maximum of 4 bytes to output 28 bits data where
+	 * max is 0xfffffff: that will cover a vsp increment of 1073742336, hence
+	 * it is sufficient for unwinding the stack.
+	 */
+	do {
+		insn = unwind_get_byte(ctrl);
+		result |= (insn & 0x7f) << (bytes * 7);
+		bytes++;
+	} while (!!(insn & 0x80) && (bytes != sizeof(result)));
+
+	return result;
+}
+
+/*
+ * Execute the current unwind instruction.
+ */
+static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
+{
+	unsigned long insn = unwind_get_byte(ctrl);
+	int ret = URC_OK;
+
+	pr_debug("%s: insn = %08lx\n", __func__, insn);
+
+	if ((insn & 0xc0) == 0x00)
+		ctrl->vrs[SP] += ((insn & 0x3f) << 2) + 4;
+	else if ((insn & 0xc0) == 0x40) {
+		ctrl->vrs[SP] -= ((insn & 0x3f) << 2) + 4;
+	} else if ((insn & 0xf0) == 0x80) {
+		unsigned long mask;
+
+		insn = (insn << 8) | unwind_get_byte(ctrl);
+		mask = insn & 0x0fff;
+		if (mask == 0) {
+			pr_warn("unwind: 'Refuse to unwind' instruction %04lx\n",
+				insn);
+			return -URC_FAILURE;
+		}
+
+		ret = unwind_exec_pop_subset_r4_to_r13(ctrl, mask);
+		if (ret)
+			goto error;
+	} else if ((insn & 0xf0) == 0x90 &&
+		   (insn & 0x0d) != 0x0d) {
+		ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
+	} else if ((insn & 0xf0) == 0xa0) {
+		ret = unwind_exec_pop_r4_to_rN(ctrl, insn);
+		if (ret)
+			goto error;
+	} else if (insn == 0xb0) {
+		if (ctrl->vrs[PC] == 0)
+			ctrl->vrs[PC] = ctrl->vrs[LR];
+		/* no further processing */
+		ctrl->entries = 0;
+	} else if (insn == 0xb1) {
+		unsigned long mask = unwind_get_byte(ctrl);
+
+		if (mask == 0 || mask & 0xf0) {
+			pr_warn("unwind: Spare encoding %04lx\n",
+				(insn << 8) | mask);
+			return -URC_FAILURE;
+		}
+
+		ret = unwind_exec_pop_subset_r0_to_r3(ctrl, mask);
+		if (ret)
+			goto error;
+	} else if (insn == 0xb2) {
+		unsigned long uleb128 = unwind_decode_uleb128(ctrl);
+
+		ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
+	} else {
+		pr_warn("unwind: Unhandled instruction %02lx\n", insn);
+		return -URC_FAILURE;
+	}
+
+	pr_debug("%s: fp = %08lx sp = %08lx lr = %08lx pc = %08lx\n", __func__,
+		 ctrl->vrs[FP], ctrl->vrs[SP], ctrl->vrs[LR], ctrl->vrs[PC]);
+
+error:
+	return ret;
+}
+
+/*
+ * Unwind a single frame starting with *sp for the symbol at *pc. It
+ * updates the *pc and *sp with the new values.
+ */
+int unwind_frame(struct stackframe *frame)
+{
+	const struct unwind_idx *idx;
+	struct unwind_ctrl_block ctrl;
+	unsigned long sp_low;
+
+	/* store the highest address on the stack to avoid crossing it*/
+	sp_low = frame->sp;
+	ctrl.sp_high = ALIGN(sp_low - THREAD_SIZE, THREAD_ALIGN)
+		       + THREAD_SIZE;
+
+	pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
+		 frame->pc, frame->lr, frame->sp);
+
+	idx = unwind_find_idx(frame->pc);
+	if (!idx) {
+		if (frame->pc && kernel_text_address(frame->pc)) {
+			if (in_module_plt(frame->pc) && frame->pc != frame->lr) {
+				/*
+				 * Quoting Ard: Veneers only set PC using a
+				 * PC+immediate LDR, and so they don't affect
+				 * the state of the stack or the register file
+				 */
+				frame->pc = frame->lr;
+				return URC_OK;
+			}
+			pr_warn("unwind: Index not found %08lx\n", frame->pc);
+		}
+		return -URC_FAILURE;
+	}
+
+	ctrl.vrs[FP] = frame->fp;
+	ctrl.vrs[SP] = frame->sp;
+	ctrl.vrs[LR] = frame->lr;
+	ctrl.vrs[PC] = 0;
+
+	if (idx->insn == 1)
+		/* can't unwind */
+		return -URC_FAILURE;
+	else if (frame->pc == prel31_to_addr(&idx->addr_offset)) {
+		/*
+		 * Unwinding is tricky when we're halfway through the prologue,
+		 * since the stack frame that the unwinder expects may not be
+		 * fully set up yet. However, one thing we do know for sure is
+		 * that if we are unwinding from the very first instruction of
+		 * a function, we are still effectively in the stack frame of
+		 * the caller, and the unwind info has no relevance yet.
+		 */
+		if (frame->pc == frame->lr)
+			return -URC_FAILURE;
+		frame->pc = frame->lr;
+		return URC_OK;
+	} else if ((idx->insn & 0x80000000) == 0)
+		/* prel31 to the unwind table */
+		ctrl.insn = (unsigned long *)prel31_to_addr(&idx->insn);
+	else if ((idx->insn & 0xff000000) == 0x80000000)
+		/* only personality routine 0 supported in the index */
+		ctrl.insn = &idx->insn;
+	else {
+		pr_warn("unwind: Unsupported personality routine %08lx in the index at %p\n",
+			idx->insn, idx);
+		return -URC_FAILURE;
+	}
+
+	/* check the personality routine */
+	if ((*ctrl.insn & 0xff000000) == 0x80000000) {
+		ctrl.byte = 2;
+		ctrl.entries = 1;
+	} else if ((*ctrl.insn & 0xff000000) == 0x81000000) {
+		ctrl.byte = 1;
+		ctrl.entries = 1 + ((*ctrl.insn & 0x00ff0000) >> 16);
+	} else {
+		pr_warn("unwind: Unsupported personality routine %08lx at %p\n",
+			*ctrl.insn, ctrl.insn);
+		return -URC_FAILURE;
+	}
+
+	ctrl.check_each_pop = 0;
+
+	if (prel31_to_addr(&idx->addr_offset) == (u32)&call_with_stack) {
+		/*
+		 * call_with_stack() is the only place where we permit SP to
+		 * jump from one stack to another, and since we know it is
+		 * guaranteed to happen, set up the SP bounds accordingly.
+		 */
+		sp_low = frame->fp;
+		ctrl.sp_high = ALIGN(frame->fp, THREAD_SIZE);
+	}
+
+	while (ctrl.entries > 0) {
+		int urc;
+		if ((ctrl.sp_high - ctrl.vrs[SP]) < sizeof(ctrl.vrs))
+			ctrl.check_each_pop = 1;
+		urc = unwind_exec_insn(&ctrl);
+		if (urc < 0)
+			return urc;
+		if (ctrl.vrs[SP] < sp_low || ctrl.vrs[SP] > ctrl.sp_high)
+			return -URC_FAILURE;
+	}
+
+	if (ctrl.vrs[PC] == 0)
+		ctrl.vrs[PC] = ctrl.vrs[LR];
+
+	/* check for infinite loop */
+	if (frame->pc == ctrl.vrs[PC] && frame->sp == ctrl.vrs[SP])
+		return -URC_FAILURE;
+
+	frame->fp = ctrl.vrs[FP];
+	frame->sp = ctrl.vrs[SP];
+	frame->lr = ctrl.vrs[LR];
+	frame->pc = ctrl.vrs[PC];
+	frame->lr_addr = ctrl.lr_addr;
+
+	return URC_OK;
+}
+
+void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
+		      const char *loglvl)
+{
+	struct stackframe frame;
+
+	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
+
+	if (!tsk)
+		tsk = current;
+
+	if (regs) {
+		arm_get_current_stackframe(regs, &frame);
+		/* PC might be corrupted, use LR in that case. */
+		if (!kernel_text_address(regs->ARM_pc))
+			frame.pc = regs->ARM_lr;
+	} else if (tsk == current) {
+		frame.fp = (unsigned long)__builtin_frame_address(0);
+		frame.sp = current_stack_pointer;
+		frame.lr = (unsigned long)__builtin_return_address(0);
+		/* We are saving the stack and execution state at this
+		 * point, so we should ensure that frame.pc is within
+		 * this block of code.
+		 */
+here:
+		frame.pc = (unsigned long)&&here;
+	} else {
+		/* task blocked in __switch_to */
+		frame.fp = thread_saved_fp(tsk);
+		frame.sp = thread_saved_sp(tsk);
+		/*
+		 * The function calling __switch_to cannot be a leaf function
+		 * so LR is recovered from the stack.
+		 */
+		frame.lr = 0;
+		frame.pc = thread_saved_pc(tsk);
+	}
+
+	while (1) {
+		int urc;
+		unsigned long where = frame.pc;
+
+		urc = unwind_frame(&frame);
+		if (urc < 0)
+			break;
+		dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl);
+	}
+}
+
+struct unwind_table *unwind_table_add(unsigned long start, unsigned long size,
+				      unsigned long text_addr,
+				      unsigned long text_size)
+{
+	unsigned long flags;
+	struct unwind_table *tab = kmalloc(sizeof(*tab), GFP_KERNEL);
+
+	pr_debug("%s(%08lx, %08lx, %08lx, %08lx)\n", __func__, start, size,
+		 text_addr, text_size);
+
+	if (!tab)
+		return tab;
+
+	tab->start = (const struct unwind_idx *)start;
+	tab->stop = (const struct unwind_idx *)(start + size);
+	tab->origin = unwind_find_origin(tab->start, tab->stop);
+	tab->begin_addr = text_addr;
+	tab->end_addr = text_addr + text_size;
+
+	raw_spin_lock_irqsave(&unwind_lock, flags);
+	list_add_tail(&tab->list, &unwind_tables);
+	raw_spin_unlock_irqrestore(&unwind_lock, flags);
+
+	return tab;
+}
+
+void unwind_table_del(struct unwind_table *tab)
+{
+	unsigned long flags;
+
+	if (!tab)
+		return;
+
+	raw_spin_lock_irqsave(&unwind_lock, flags);
+	list_del(&tab->list);
+	raw_spin_unlock_irqrestore(&unwind_lock, flags);
+
+	kfree(tab);
+}