[PATCH 2/3] ARM: Add stack unwinding support
Sascha Hauer
s.hauer at pengutronix.de
Tue Mar 8 06:24:51 EST 2011
Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
arch/arm/Kconfig | 10 ++
arch/arm/Makefile | 4 +
arch/arm/cpu/interrupts.c | 4 +
arch/arm/lib/Makefile | 2 +-
arch/arm/lib/barebox.lds.S | 16 ++
arch/arm/lib/unwind.c | 344 ++++++++++++++++++++++++++++++++++++++++++++
6 files changed, 379 insertions(+), 1 deletions(-)
create mode 100644 arch/arm/lib/unwind.c
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index bc54e58..aae0e99 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -115,6 +115,16 @@ config ARM_OPTIMZED_STRING_FUNCTIONS
These functions work much faster than the normal versions but
increase your binary size.
+config ARM_UNWIND
+ bool "enable stack unwinding support"
+ depends on AEABI
+ help
+ This option enables stack unwinding support in barebox
+ using the information automatically generated by the
+ compiler. The resulting kernel image is slightly bigger but
+ the performance is not affected. Currently, this feature
+ only works with EABI compilers. If unsure say Y.
+
endmenu
source common/Kconfig
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index d075efd..697c783 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -34,6 +34,10 @@ else
CFLAGS_ABI :=$(call cc-option,-mapcs-32,-mabi=apcs-gnu) $(call cc-option,-mno-thumb-interwork,)
endif
+ifeq ($(CONFIG_ARM_UNWIND),y)
+CFLAGS_ABI +=-funwind-tables
+endif
+
CPPFLAGS += $(CFLAGS_ABI) $(arch-y) $(tune-y)
AFLAGS += -include asm/unified.h
diff --git a/arch/arm/cpu/interrupts.c b/arch/arm/cpu/interrupts.c
index 4a0b3f8..5168921 100644
--- a/arch/arm/cpu/interrupts.c
+++ b/arch/arm/cpu/interrupts.c
@@ -27,6 +27,7 @@
#include <common.h>
#include <asm/ptrace.h>
+#include <asm/unwind.h>
void do_undefined_instruction (struct pt_regs *pt_regs);
void do_software_interrupt (struct pt_regs *pt_regs);
@@ -115,6 +116,9 @@ void show_regs (struct pt_regs *regs)
fast_interrupts_enabled (regs) ? "on" : "off",
processor_modes[processor_mode (regs)],
thumb_mode (regs) ? " (T)" : "");
+#ifdef CONFIG_ARM_UNWIND
+ unwind_backtrace(regs);
+#endif
}
/**
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 89cb72b..3a01083 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -14,7 +14,7 @@ obj-y += ashldi3.o
obj-y += lshrdi3.o
obj-$(CONFIG_ARM_OPTIMZED_STRING_FUNCTIONS) += memcpy.o
obj-$(CONFIG_ARM_OPTIMZED_STRING_FUNCTIONS) += memset.o
-
+obj-$(CONFIG_ARM_UNWIND) += unwind.o
obj-$(CONFIG_MODULES) += module.o
extra-$(CONFIG_GENERIC_LINKER_SCRIPT) += barebox.lds
diff --git a/arch/arm/lib/barebox.lds.S b/arch/arm/lib/barebox.lds.S
index cc74b2f..7683f73 100644
--- a/arch/arm/lib/barebox.lds.S
+++ b/arch/arm/lib/barebox.lds.S
@@ -51,6 +51,22 @@ SECTIONS
. = ALIGN(4);
.rodata : { *(.rodata*) }
+#ifdef CONFIG_ARM_UNWIND
+ /*
+ * Stack unwinding tables
+ */
+ . = ALIGN(8);
+ .ARM.unwind_idx : {
+ __start_unwind_idx = .;
+ *(.ARM.exidx*)
+ __stop_unwind_idx = .;
+ }
+ .ARM.unwind_tab : {
+ __start_unwind_tab = .;
+ *(.ARM.extab*)
+ __stop_unwind_tab = .;
+ }
+#endif
_etext = .; /* End of text and rodata section */
. = ALIGN(4);
diff --git a/arch/arm/lib/unwind.c b/arch/arm/lib/unwind.c
new file mode 100644
index 0000000..62d26af
--- /dev/null
+++ b/arch/arm/lib/unwind.c
@@ -0,0 +1,344 @@
+#include <common.h>
+#include <init.h>
+#include <asm/stacktrace.h>
+#include <asm/unwind.h>
+#include <asm-generic/sections.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 */
+ unsigned long *insn; /* pointer to the current instructions word */
+ int entries; /* number of entries left to interpret */
+ int byte; /* current byte number in the instructions word */
+};
+
+enum regs {
+ FP = 11,
+ SP = 13,
+ LR = 14,
+ PC = 15
+};
+
+#define THREAD_SIZE 8192
+
+extern struct unwind_idx __start_unwind_idx[];
+extern struct unwind_idx __stop_unwind_idx[];
+
+/* 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; \
+})
+
+static inline int is_kernel_text(unsigned long addr)
+{
+ if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext))
+ return 1;
+ return 0;
+}
+
+void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long frame)
+{
+#ifdef CONFIG_KALLSYMS
+ printk("[<%08lx>] (%pS) from [<%08lx>] (%pS)\n", where, (void *)where, from, (void *)from);
+#else
+ printk("Function entered at [<%08lx>] from [<%08lx>]\n", where, from);
+#endif
+}
+
+/*
+ * Binary search in the unwind index. The entries entries are
+ * guaranteed to be sorted in ascending order by the linker.
+ */
+static struct unwind_idx *search_index(unsigned long addr,
+ struct unwind_idx *first,
+ struct unwind_idx *last)
+{
+ pr_debug("%s(%08lx, %p, %p)\n", __func__, addr, first, last);
+
+ if (addr < first->addr) {
+ pr_warning("unwind: Unknown symbol address %08lx\n", addr);
+ return NULL;
+ } else if (addr >= last->addr)
+ return last;
+
+ while (first < last - 1) {
+ struct unwind_idx *mid = first + ((last - first + 1) >> 1);
+
+ if (addr < mid->addr)
+ last = mid;
+ else
+ first = mid;
+ }
+
+ return first;
+}
+
+static struct unwind_idx *unwind_find_idx(unsigned long addr)
+{
+ struct unwind_idx *idx = NULL;
+
+ pr_debug("%s(%08lx)\n", __func__, addr);
+
+ if (is_kernel_text(addr))
+ /* main unwind table */
+ idx = search_index(addr, __start_unwind_idx,
+ __stop_unwind_idx - 1);
+ else {
+ /* module unwinding not supported */
+ }
+
+ 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_warning("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;
+}
+
+/*
+ * Execute the current unwind instruction.
+ */
+static int unwind_exec_insn(struct unwind_ctrl_block *ctrl)
+{
+ unsigned long insn = unwind_get_byte(ctrl);
+
+ 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;
+ unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
+ int load_sp, reg = 4;
+
+ insn = (insn << 8) | unwind_get_byte(ctrl);
+ mask = insn & 0x0fff;
+ if (mask == 0) {
+ pr_warning("unwind: 'Refuse to unwind' instruction %04lx\n",
+ insn);
+ return -URC_FAILURE;
+ }
+
+ /* pop R4-R15 according to mask */
+ load_sp = mask & (1 << (13 - 4));
+ while (mask) {
+ if (mask & 1)
+ ctrl->vrs[reg] = *vsp++;
+ mask >>= 1;
+ reg++;
+ }
+ if (!load_sp)
+ ctrl->vrs[SP] = (unsigned long)vsp;
+ } else if ((insn & 0xf0) == 0x90 &&
+ (insn & 0x0d) != 0x0d)
+ ctrl->vrs[SP] = ctrl->vrs[insn & 0x0f];
+ else if ((insn & 0xf0) == 0xa0) {
+ unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
+ int reg;
+
+ /* pop R4-R[4+bbb] */
+ for (reg = 4; reg <= 4 + (insn & 7); reg++)
+ ctrl->vrs[reg] = *vsp++;
+ if (insn & 0x80)
+ ctrl->vrs[14] = *vsp++;
+ ctrl->vrs[SP] = (unsigned long)vsp;
+ } 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);
+ unsigned long *vsp = (unsigned long *)ctrl->vrs[SP];
+ int reg = 0;
+
+ if (mask == 0 || mask & 0xf0) {
+ pr_warning("unwind: Spare encoding %04lx\n",
+ (insn << 8) | mask);
+ return -URC_FAILURE;
+ }
+
+ /* pop R0-R3 according to mask */
+ while (mask) {
+ if (mask & 1)
+ ctrl->vrs[reg] = *vsp++;
+ mask >>= 1;
+ reg++;
+ }
+ ctrl->vrs[SP] = (unsigned long)vsp;
+ } else if (insn == 0xb2) {
+ unsigned long uleb128 = unwind_get_byte(ctrl);
+
+ ctrl->vrs[SP] += 0x204 + (uleb128 << 2);
+ } else {
+ pr_warning("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]);
+
+ return URC_OK;
+}
+
+/*
+ * 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)
+{
+ unsigned long high, low;
+ struct unwind_idx *idx;
+ struct unwind_ctrl_block ctrl;
+
+ /* only go to a higher address on the stack */
+ low = frame->sp;
+ high = ALIGN(low, THREAD_SIZE);
+
+ pr_debug("%s(pc = %08lx lr = %08lx sp = %08lx)\n", __func__,
+ frame->pc, frame->lr, frame->sp);
+
+ if (!is_kernel_text(frame->pc))
+ return -URC_FAILURE;
+
+ idx = unwind_find_idx(frame->pc);
+ if (!idx) {
+ pr_warning("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 ((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_warning("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_warning("unwind: Unsupported personality routine %08lx at %p\n",
+ *ctrl.insn, ctrl.insn);
+ return -URC_FAILURE;
+ }
+
+ while (ctrl.entries > 0) {
+ int urc = unwind_exec_insn(&ctrl);
+ if (urc < 0)
+ return urc;
+ if (ctrl.vrs[SP] < low || ctrl.vrs[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])
+ return -URC_FAILURE;
+
+ frame->fp = ctrl.vrs[FP];
+ frame->sp = ctrl.vrs[SP];
+ frame->lr = ctrl.vrs[LR];
+ frame->pc = ctrl.vrs[PC];
+
+ return URC_OK;
+}
+
+void unwind_backtrace(struct pt_regs *regs)
+{
+ struct stackframe frame;
+ register unsigned long current_sp asm ("sp");
+
+ pr_debug("%s\n", __func__);
+
+ if (regs) {
+ frame.fp = regs->ARM_fp;
+ frame.sp = regs->ARM_sp;
+ frame.lr = regs->ARM_lr;
+ /* PC might be corrupted, use LR in that case. */
+ frame.pc = is_kernel_text(regs->ARM_pc)
+ ? regs->ARM_pc : regs->ARM_lr;
+ } else {
+ frame.sp = current_sp;
+ frame.lr = (unsigned long)__builtin_return_address(0);
+ frame.pc = (unsigned long)unwind_backtrace;
+ }
+
+ 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);
+ }
+}
+
+static int unwind_init(void)
+{
+ struct unwind_idx *idx;
+
+ /* Convert the symbol addresses to absolute values */
+ for (idx = __start_unwind_idx; idx < __stop_unwind_idx; idx++)
+ idx->addr = prel31_to_addr(&idx->addr);
+
+ return 0;
+}
+core_initcall(unwind_init);
--
1.7.2.3
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