metag: Stack unwinding

Add stack unwinding support for metag.

Signed-off-by: James Hogan <james.hogan@imgtec.com>

2 files changed, 207 insertions, 0 deletions

diff --git a/arch/metag/include/asm/stacktrace.h b/arch/metag/include/asm/stacktrace.h
new file mode 100644
index 000000000000..2830a0fe7ac9
--- /dev/null
+++ b/arch/metag/include/asm/stacktrace.h
@@ -0,0 +1,20 @@
+#ifndef __ASM_STACKTRACE_H
+#define __ASM_STACKTRACE_H
+
+struct stackframe {
+        unsigned long fp;
+        unsigned long sp;
+        unsigned long lr;
+        unsigned long pc;
+};
+
+struct metag_frame {
+        unsigned long fp;
+        unsigned long lr;
+};
+
+extern int unwind_frame(struct stackframe *frame);
+extern void walk_stackframe(struct stackframe *frame,
+                            int (*fn)(struct stackframe *, void *), void *data);
+
+#endif  /* __ASM_STACKTRACE_H */
diff --git a/arch/metag/kernel/stacktrace.c b/arch/metag/kernel/stacktrace.c
new file mode 100644
index 000000000000..5510361d5bea
--- /dev/null
+++ b/arch/metag/kernel/stacktrace.c
@@ -0,0 +1,187 @@
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/stacktrace.h>
+
+#include <asm/stacktrace.h>
+
+#if defined(CONFIG_FRAME_POINTER)
+
+#ifdef CONFIG_KALLSYMS
+#include <linux/kallsyms.h>
+#include <linux/module.h>
+
+static unsigned long tbi_boing_addr;
+static unsigned long tbi_boing_size;
+
+static void tbi_boing_init(void)
+{
+        /* We need to know where TBIBoingVec is and it's size */
+        unsigned long size;
+        unsigned long offset;
+        char modname[MODULE_NAME_LEN];
+        char name[KSYM_NAME_LEN];
+        tbi_boing_addr = kallsyms_lookup_name("___TBIBoingVec");
+        if (!tbi_boing_addr)
+                tbi_boing_addr = 1;
+        else if (!lookup_symbol_attrs(tbi_boing_addr, &size,
+                                      &offset, modname, name))
+                tbi_boing_size = size;
+}
+#endif
+
+#define ALIGN_DOWN(addr, size)  ((addr)&(~((size)-1)))
+
+/*
+ * Unwind the current stack frame and store the new register values in the
+ * structure passed as argument. Unwinding is equivalent to a function return,
+ * hence the new PC value rather than LR should be used for backtrace.
+ */
+int notrace unwind_frame(struct stackframe *frame)
+{
+        struct metag_frame *fp = (struct metag_frame *)frame->fp;
+        unsigned long lr;
+        unsigned long fpnew;
+
+        if (frame->fp & 0x7)
+                return -EINVAL;
+
+        fpnew = fp->fp;
+        lr = fp->lr - 4;
+
+#ifdef CONFIG_KALLSYMS
+        /* If we've reached TBIBoingVec then we're at an interrupt
+         * entry point or a syscall entry point. The frame pointer
+         * points to a pt_regs which can be used to continue tracing on
+         * the other side of the boing.
+         */
+        if (!tbi_boing_addr)
+                tbi_boing_init();
+        if (tbi_boing_size && lr >= tbi_boing_addr &&
+            lr < tbi_boing_addr + tbi_boing_size) {
+                struct pt_regs *regs = (struct pt_regs *)fpnew;
+                if (user_mode(regs))
+                        return -EINVAL;
+                fpnew = regs->ctx.AX[1].U0;
+                lr = regs->ctx.DX[4].U1;
+        }
+#endif
+
+        /* stack grows up, so frame pointers must decrease */
+        if (fpnew < (ALIGN_DOWN((unsigned long)fp, THREAD_SIZE) +
+                     sizeof(struct thread_info)) || fpnew >= (unsigned long)fp)
+                return -EINVAL;
+
+        /* restore the registers from the stack frame */
+        frame->fp = fpnew;
+        frame->pc = lr;
+
+        return 0;
+}
+#else
+int notrace unwind_frame(struct stackframe *frame)
+{
+        struct metag_frame *sp = (struct metag_frame *)frame->sp;
+
+        if (frame->sp & 0x7)
+                return -EINVAL;
+
+        while (!kstack_end(sp)) {
+                unsigned long addr = sp->lr - 4;
+                sp--;
+
+                if (__kernel_text_address(addr)) {
+                        frame->sp = (unsigned long)sp;
+                        frame->pc = addr;
+                        return 0;
+                }
+        }
+        return -EINVAL;
+}
+#endif
+
+void notrace walk_stackframe(struct stackframe *frame,
+                     int (*fn)(struct stackframe *, void *), void *data)
+{
+        while (1) {
+                int ret;
+
+                if (fn(frame, data))
+                        break;
+                ret = unwind_frame(frame);
+                if (ret < 0)
+                        break;
+        }
+}
+EXPORT_SYMBOL(walk_stackframe);
+
+#ifdef CONFIG_STACKTRACE
+struct stack_trace_data {
+        struct stack_trace *trace;
+        unsigned int no_sched_functions;
+        unsigned int skip;
+};
+
+static int save_trace(struct stackframe *frame, void *d)
+{
+        struct stack_trace_data *data = d;
+        struct stack_trace *trace = data->trace;
+        unsigned long addr = frame->pc;
+
+        if (data->no_sched_functions && in_sched_functions(addr))
+                return 0;
+        if (data->skip) {
+                data->skip--;
+                return 0;
+        }
+
+        trace->entries[trace->nr_entries++] = addr;
+
+        return trace->nr_entries >= trace->max_entries;
+}
+
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+        struct stack_trace_data data;
+        struct stackframe frame;
+
+        data.trace = trace;
+        data.skip = trace->skip;
+
+        if (tsk != current) {
+#ifdef CONFIG_SMP
+                /*
+                 * What guarantees do we have here that 'tsk' is not
+                 * running on another CPU?  For now, ignore it as we
+                 * can't guarantee we won't explode.
+                 */
+                if (trace->nr_entries < trace->max_entries)
+                        trace->entries[trace->nr_entries++] = ULONG_MAX;
+                return;
+#else
+                data.no_sched_functions = 1;
+                frame.fp = thread_saved_fp(tsk);
+                frame.sp = thread_saved_sp(tsk);
+                frame.lr = 0;           /* recovered from the stack */
+                frame.pc = thread_saved_pc(tsk);
+#endif
+        } else {
+                register unsigned long current_sp asm ("A0StP");
+
+                data.no_sched_functions = 0;
+                frame.fp = (unsigned long)__builtin_frame_address(0);
+                frame.sp = current_sp;
+                frame.lr = (unsigned long)__builtin_return_address(0);
+                frame.pc = (unsigned long)save_stack_trace_tsk;
+        }
+
+        walk_stackframe(&frame, save_trace, &data);
+        if (trace->nr_entries < trace->max_entries)
+                trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
+
+void save_stack_trace(struct stack_trace *trace)
+{
+        save_stack_trace_tsk(current, trace);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+#endif