sh: Move over sh64 switch_to and stack unwinder.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 326 insertions, 0 deletions

diff --git a/arch/sh/kernel/cpu/sh5/unwind.c b/arch/sh/kernel/cpu/sh5/unwind.c
new file mode 100644
index 00000000000..1214c78e358
--- /dev/null
+++ b/arch/sh/kernel/cpu/sh5/unwind.c
@@ -0,0 +1,326 @@
+/*
+ * arch/sh64/kernel/unwind.c
+ *
+ * Copyright (C) 2004  Paul Mundt
+ * Copyright (C) 2004  Richard Curnow
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/kallsyms.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <asm/page.h>
+#include <asm/ptrace.h>
+#include <asm/processor.h>
+#include <asm/io.h>
+
+static u8 regcache[63];
+
+/*
+ * Finding the previous stack frame isn't horribly straightforward as it is
+ * on some other platforms. In the sh64 case, we don't have "linked" stack
+ * frames, so we need to do a bit of work to determine the previous frame,
+ * and in turn, the previous r14/r18 pair.
+ *
+ * There are generally a few cases which determine where we can find out
+ * the r14/r18 values. In the general case, this can be determined by poking
+ * around the prologue of the symbol PC is in (note that we absolutely must
+ * have frame pointer support as well as the kernel symbol table mapped,
+ * otherwise we can't even get this far).
+ *
+ * In other cases, such as the interrupt/exception path, we can poke around
+ * the sp/fp.
+ *
+ * Notably, this entire approach is somewhat error prone, and in the event
+ * that the previous frame cannot be determined, that's all we can do.
+ * Either way, this still leaves us with a more correct backtrace then what
+ * we would be able to come up with by walking the stack (which is garbage
+ * for anything beyond the first frame).
+ *						-- PFM.
+ */
+static int lookup_prev_stack_frame(unsigned long fp, unsigned long pc,
+		      unsigned long *pprev_fp, unsigned long *pprev_pc,
+		      struct pt_regs *regs)
+{
+	const char *sym;
+	char namebuf[128];
+	unsigned long offset;
+	unsigned long prologue = 0;
+	unsigned long fp_displacement = 0;
+	unsigned long fp_prev = 0;
+	unsigned long offset_r14 = 0, offset_r18 = 0;
+	int i, found_prologue_end = 0;
+
+	sym = kallsyms_lookup(pc, NULL, &offset, NULL, namebuf);
+	if (!sym)
+		return -EINVAL;
+
+	prologue = pc - offset;
+	if (!prologue)
+		return -EINVAL;
+
+	/* Validate fp, to avoid risk of dereferencing a bad pointer later.
+	   Assume 128Mb since that's the amount of RAM on a Cayman.  Modify
+	   when there is an SH-5 board with more. */
+	if ((fp < (unsigned long) phys_to_virt(__MEMORY_START)) ||
+	    (fp >= (unsigned long)(phys_to_virt(__MEMORY_START)) + 128*1024*1024) ||
+	    ((fp & 7) != 0)) {
+		return -EINVAL;
+	}
+
+	/*
+	 * Depth to walk, depth is completely arbitrary.
+	 */
+	for (i = 0; i < 100; i++, prologue += sizeof(unsigned long)) {
+		unsigned long op;
+		u8 major, minor;
+		u8 src, dest, disp;
+
+		op = *(unsigned long *)prologue;
+
+		major = (op >> 26) & 0x3f;
+		src   = (op >> 20) & 0x3f;
+		minor = (op >> 16) & 0xf;
+		disp  = (op >> 10) & 0x3f;
+		dest  = (op >>  4) & 0x3f;
+
+		/*
+		 * Stack frame creation happens in a number of ways.. in the
+		 * general case when the stack frame is less than 511 bytes,
+		 * it's generally created by an addi or addi.l:
+		 *
+		 *	addi/addi.l r15, -FRAME_SIZE, r15
+		 *
+		 * in the event that the frame size is bigger than this, it's
+		 * typically created using a movi/sub pair as follows:
+		 *
+		 *	movi	FRAME_SIZE, rX
+		 *	sub	r15, rX, r15
+		 */
+
+		switch (major) {
+		case (0x00 >> 2):
+			switch (minor) {
+			case 0x8: /* add.l */
+			case 0x9: /* add */
+				/* Look for r15, r63, r14 */
+				if (src == 15 && disp == 63 && dest == 14)
+					found_prologue_end = 1;
+
+				break;
+			case 0xa: /* sub.l */
+			case 0xb: /* sub */
+				if (src != 15 || dest != 15)
+					continue;
+
+				fp_displacement -= regcache[disp];
+				fp_prev = fp - fp_displacement;
+				break;
+			}
+			break;
+		case (0xa8 >> 2): /* st.l */
+			if (src != 15)
+				continue;
+
+			switch (dest) {
+			case 14:
+				if (offset_r14 || fp_displacement == 0)
+					continue;
+
+				offset_r14 = (u64)(((((s64)op >> 10) & 0x3ff) << 54) >> 54);
+				offset_r14 *= sizeof(unsigned long);
+				offset_r14 += fp_displacement;
+				break;
+			case 18:
+				if (offset_r18 || fp_displacement == 0)
+					continue;
+
+				offset_r18 = (u64)(((((s64)op >> 10) & 0x3ff) << 54) >> 54);
+				offset_r18 *= sizeof(unsigned long);
+				offset_r18 += fp_displacement;
+				break;
+			}
+
+			break;
+		case (0xcc >> 2): /* movi */
+			if (dest >= 63) {
+				printk(KERN_NOTICE "%s: Invalid dest reg %d "
+				       "specified in movi handler. Failed "
+				       "opcode was 0x%lx: ", __FUNCTION__,
+				       dest, op);
+
+				continue;
+			}
+
+			/* Sign extend */
+			regcache[dest] =
+				((((s64)(u64)op >> 10) & 0xffff) << 54) >> 54;
+			break;
+		case (0xd0 >> 2): /* addi */
+		case (0xd4 >> 2): /* addi.l */
+			/* Look for r15, -FRAME_SIZE, r15 */
+			if (src != 15 || dest != 15)
+				continue;
+
+			/* Sign extended frame size.. */
+			fp_displacement +=
+				(u64)(((((s64)op >> 10) & 0x3ff) << 54) >> 54);
+			fp_prev = fp - fp_displacement;
+			break;
+		}
+
+		if (found_prologue_end && offset_r14 && (offset_r18 || *pprev_pc) && fp_prev)
+			break;
+	}
+
+	if (offset_r14 == 0 || fp_prev == 0) {
+		if (!offset_r14)
+			pr_debug("Unable to find r14 offset\n");
+		if (!fp_prev)
+			pr_debug("Unable to find previous fp\n");
+
+		return -EINVAL;
+	}
+
+	/* For innermost leaf function, there might not be a offset_r18 */
+	if (!*pprev_pc && (offset_r18 == 0))
+		return -EINVAL;
+
+	*pprev_fp = *(unsigned long *)(fp_prev + offset_r14);
+
+	if (offset_r18)
+		*pprev_pc = *(unsigned long *)(fp_prev + offset_r18);
+
+	*pprev_pc &= ~1;
+
+	return 0;
+}
+
+/* Don't put this on the stack since we'll want to call sh64_unwind
+ * when we're close to underflowing the stack anyway. */
+static struct pt_regs here_regs;
+
+extern const char syscall_ret;
+extern const char ret_from_syscall;
+extern const char ret_from_exception;
+extern const char ret_from_irq;
+
+static void sh64_unwind_inner(struct pt_regs *regs);
+
+static void unwind_nested (unsigned long pc, unsigned long fp)
+{
+	if ((fp >= __MEMORY_START) &&
+	    ((fp & 7) == 0)) {
+		sh64_unwind_inner((struct pt_regs *) fp);
+	}
+}
+
+static void sh64_unwind_inner(struct pt_regs *regs)
+{
+	unsigned long pc, fp;
+	int ofs = 0;
+	int first_pass;
+
+	pc = regs->pc & ~1;
+	fp = regs->regs[14];
+
+	first_pass = 1;
+	for (;;) {
+		int cond;
+		unsigned long next_fp, next_pc;
+
+		if (pc == ((unsigned long) &syscall_ret & ~1)) {
+			printk("SYSCALL\n");
+			unwind_nested(pc,fp);
+			return;
+		}
+
+		if (pc == ((unsigned long) &ret_from_syscall & ~1)) {
+			printk("SYSCALL (PREEMPTED)\n");
+			unwind_nested(pc,fp);
+			return;
+		}
+
+		/* In this case, the PC is discovered by lookup_prev_stack_frame but
+		   it has 4 taken off it to look like the 'caller' */
+		if (pc == ((unsigned long) &ret_from_exception & ~1)) {
+			printk("EXCEPTION\n");
+			unwind_nested(pc,fp);
+			return;
+		}
+
+		if (pc == ((unsigned long) &ret_from_irq & ~1)) {
+			printk("IRQ\n");
+			unwind_nested(pc,fp);
+			return;
+		}
+
+		cond = ((pc >= __MEMORY_START) && (fp >= __MEMORY_START) &&
+			((pc & 3) == 0) && ((fp & 7) == 0));
+
+		pc -= ofs;
+
+		printk("[<%08lx>] ", pc);
+		print_symbol("%s\n", pc);
+
+		if (first_pass) {
+			/* If the innermost frame is a leaf function, it's
+			 * possible that r18 is never saved out to the stack.
+			 */
+			next_pc = regs->regs[18];
+		} else {
+			next_pc = 0;
+		}
+
+		if (lookup_prev_stack_frame(fp, pc, &next_fp, &next_pc, regs) == 0) {
+			ofs = sizeof(unsigned long);
+			pc = next_pc & ~1;
+			fp = next_fp;
+		} else {
+			printk("Unable to lookup previous stack frame\n");
+			break;
+		}
+		first_pass = 0;
+	}
+
+	printk("\n");
+
+}
+
+void sh64_unwind(struct pt_regs *regs)
+{
+	if (!regs) {
+		/*
+		 * Fetch current regs if we have no other saved state to back
+		 * trace from.
+		 */
+		regs = &here_regs;
+
+		__asm__ __volatile__ ("ori r14, 0, %0" : "=r" (regs->regs[14]));
+		__asm__ __volatile__ ("ori r15, 0, %0" : "=r" (regs->regs[15]));
+		__asm__ __volatile__ ("ori r18, 0, %0" : "=r" (regs->regs[18]));
+
+		__asm__ __volatile__ ("gettr tr0, %0" : "=r" (regs->tregs[0]));
+		__asm__ __volatile__ ("gettr tr1, %0" : "=r" (regs->tregs[1]));
+		__asm__ __volatile__ ("gettr tr2, %0" : "=r" (regs->tregs[2]));
+		__asm__ __volatile__ ("gettr tr3, %0" : "=r" (regs->tregs[3]));
+		__asm__ __volatile__ ("gettr tr4, %0" : "=r" (regs->tregs[4]));
+		__asm__ __volatile__ ("gettr tr5, %0" : "=r" (regs->tregs[5]));
+		__asm__ __volatile__ ("gettr tr6, %0" : "=r" (regs->tregs[6]));
+		__asm__ __volatile__ ("gettr tr7, %0" : "=r" (regs->tregs[7]));
+
+		__asm__ __volatile__ (
+			"pta 0f, tr0\n\t"
+			"blink tr0, %0\n\t"
+			"0: nop"
+			: "=r" (regs->pc)
+		);
+	}
+
+	printk("\nCall Trace:\n");
+	sh64_unwind_inner(regs);
+}
+