Merge git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile

* git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile:
  arch/tile: convert a BUG_ON to BUILD_BUG_ON
  arch/tile: make ptrace() work properly for TILE-Gx COMPAT mode
  arch/tile: support new info op generated by compiler
  arch/tile: minor whitespace/naming changes for string support files
  arch/tile: enable single-step support for TILE-Gx
  arch/tile: parameterize system PLs to support KVM port
  arch/tile: add Tilera's <arch/sim.h> header as an open-source header
  arch/tile: Bomb C99 comments to C89 comments in tile's <arch/sim_def.h>
  arch/tile: prevent corrupt top frame from causing backtracer runaway
  arch/tile: various top-level Makefile cleanups
  arch/tile: change lower bound on syscall error return to -4095
  arch/tile: properly export __mb_incoherent for modules
  arch/tile: provide a definition of MAP_STACK
  kmemleak: add TILE to the list of supported architectures.
  char: hvc: check for error case
  arch/tile: Add a warning if we try to allocate too much vmalloc memory.
  arch/tile: update some comments to clarify register usage.
  arch/tile: use better "punctuation" for VMSPLIT_3_5G and friends
  arch/tile: Use <asm-generic/syscalls.h>
  tile: replace some BUG_ON checks with BUILD_BUG_ON checks

1 files changed, 72 insertions, 1 deletions

diff --git a/arch/tile/kernel/single_step.c b/arch/tile/kernel/single_step.c
index 5ec4b9c..1eb3b39 100644
--- a/arch/tile/kernel/single_step.c
+++ b/arch/tile/kernel/single_step.c
@@ -15,7 +15,7 @@
  * Derived from iLib's single-stepping code.
  */
 
-#ifndef __tilegx__   /* No support for single-step yet. */
+#ifndef __tilegx__   /* Hardware support for single step unavailable. */
 
 /* These functions are only used on the TILE platform */
 #include <linux/slab.h>
@@ -660,4 +660,75 @@ void single_step_once(struct pt_regs *regs)
 		regs->pc += 8;
 }
 
+#else
+#include <linux/smp.h>
+#include <linux/ptrace.h>
+#include <arch/spr_def.h>
+
+static DEFINE_PER_CPU(unsigned long, ss_saved_pc);
+
+
+/*
+ * Called directly on the occasion of an interrupt.
+ *
+ * If the process doesn't have single step set, then we use this as an
+ * opportunity to turn single step off.
+ *
+ * It has been mentioned that we could conditionally turn off single stepping
+ * on each entry into the kernel and rely on single_step_once to turn it
+ * on for the processes that matter (as we already do), but this
+ * implementation is somewhat more efficient in that we muck with registers
+ * once on a bum interrupt rather than on every entry into the kernel.
+ *
+ * If SINGLE_STEP_CONTROL_K has CANCELED set, then an interrupt occurred,
+ * so we have to run through this process again before we can say that an
+ * instruction has executed.
+ *
+ * swint will set CANCELED, but it's a legitimate instruction.  Fortunately
+ * it changes the PC.  If it hasn't changed, then we know that the interrupt
+ * wasn't generated by swint and we'll need to run this process again before
+ * we can say an instruction has executed.
+ *
+ * If either CANCELED == 0 or the PC's changed, we send out SIGTRAPs and get
+ * on with our lives.
+ */
+
+void gx_singlestep_handle(struct pt_regs *regs, int fault_num)
+{
+	unsigned long *ss_pc = &__get_cpu_var(ss_saved_pc);
+	struct thread_info *info = (void *)current_thread_info();
+	int is_single_step = test_ti_thread_flag(info, TIF_SINGLESTEP);
+	unsigned long control = __insn_mfspr(SPR_SINGLE_STEP_CONTROL_K);
+
+	if (is_single_step == 0) {
+		__insn_mtspr(SPR_SINGLE_STEP_EN_K_K, 0);
+
+	} else if ((*ss_pc != regs->pc) ||
+		   (!(control & SPR_SINGLE_STEP_CONTROL_1__CANCELED_MASK))) {
+
+		ptrace_notify(SIGTRAP);
+		control |= SPR_SINGLE_STEP_CONTROL_1__CANCELED_MASK;
+		control |= SPR_SINGLE_STEP_CONTROL_1__INHIBIT_MASK;
+		__insn_mtspr(SPR_SINGLE_STEP_CONTROL_K, control);
+	}
+}
+
+
+/*
+ * Called from need_singlestep.  Set up the control registers and the enable
+ * register, then return back.
+ */
+
+void single_step_once(struct pt_regs *regs)
+{
+	unsigned long *ss_pc = &__get_cpu_var(ss_saved_pc);
+	unsigned long control = __insn_mfspr(SPR_SINGLE_STEP_CONTROL_K);
+
+	*ss_pc = regs->pc;
+	control |= SPR_SINGLE_STEP_CONTROL_1__CANCELED_MASK;
+	control |= SPR_SINGLE_STEP_CONTROL_1__INHIBIT_MASK;
+	__insn_mtspr(SPR_SINGLE_STEP_CONTROL_K, control);
+	__insn_mtspr(SPR_SINGLE_STEP_EN_K_K, 1 << USER_PL);
+}
+
 #endif /* !__tilegx__ */