Revert "MIPS: Add basic support for ptrace single step"

This reverts commit 7c86ff99.

There are too many special cases for MIPS not covered by this patch.
In the end it might be better to implement single stepping in userland
than emulating it in the kernel.
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/include/asm/ptrace.h

@@ -186,6 +186,4 @@ static inline void user_stack_pointer_set(struct pt_regs *regs,
 	regs->regs[29] = val;
 }
 
-#define arch_has_single_step()	(1)
-
 #endif /* _ASM_PTRACE_H */

arch/mips/include/asm/thread_info.h

@@ -35,10 +35,6 @@ struct thread_info {
 						 */
 	struct pt_regs		*regs;
 	long			syscall;	/* syscall number */
-
-	int bpt_nsaved;
-	unsigned long bpt_addr[1];		/* breakpoint handling */
-	unsigned int bpt_insn[1];
 };
 
 /*
@@ -121,7 +117,6 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_UPROBE		6	/* breakpointed or singlestepping */
 #define TIF_NOTIFY_SIGNAL	7	/* signal notifications exist */
 #define TIF_RESTORE_SIGMASK	9	/* restore signal mask in do_signal() */
-#define TIF_SINGLESTEP		10	/* restore singlestep on return to user mode */
 #define TIF_USEDFPU		16	/* FPU was used by this task this quantum (SMP) */
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
 #define TIF_NOHZ		19	/* in adaptive nohz mode */

arch/mips/kernel/ptrace.c

@@ -45,15 +45,10 @@
 #include <linux/uaccess.h>
 #include <asm/bootinfo.h>
 #include <asm/reg.h>
-#include <asm/branch.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/syscalls.h>
 
-#include "probes-common.h"
-
-#define BREAKINST	0x0000000d
-
 /*
  * Called by kernel/ptrace.c when detaching..
  *
@@ -63,7 +58,6 @@ void ptrace_disable(struct task_struct *child)
 {
 	/* Don't load the watchpoint registers for the ex-child. */
 	clear_tsk_thread_flag(child, TIF_LOAD_WATCH);
-	user_disable_single_step(child);
 }
 
 /*
@@ -1078,108 +1072,6 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
 #endif
 }
 
-static int read_insn(struct task_struct *task, unsigned long addr, unsigned int *insn)
-{
-	int copied = access_process_vm(task, addr, insn,
-				       sizeof(unsigned int), FOLL_FORCE);
-
-	if (copied != sizeof(unsigned int)) {
-		pr_err("failed to read instruction from 0x%lx\n", addr);
-		return -EIO;
-	}
-
-	return 0;
-}
-
-static int write_insn(struct task_struct *task, unsigned long addr, unsigned int insn)
-{
-	int copied = access_process_vm(task, addr, &insn,
-				       sizeof(unsigned int), FOLL_FORCE | FOLL_WRITE);
-
-	if (copied != sizeof(unsigned int)) {
-		pr_err("failed to write instruction to 0x%lx\n", addr);
-		return -EIO;
-	}
-
-	return 0;
-}
-
-static int insn_has_delayslot(union mips_instruction insn)
-{
-	return __insn_has_delay_slot(insn);
-}
-
-static void ptrace_set_bpt(struct task_struct *child)
-{
-	union mips_instruction mips_insn = { 0 };
-	struct pt_regs *regs;
-	unsigned long pc;
-	unsigned int insn;
-	int i, ret, nsaved = 0;
-
-	regs = task_pt_regs(child);
-	pc = regs->cp0_epc;
-
-	ret = read_insn(child, pc, &insn);
-	if (ret < 0)
-		return;
-
-	if (insn_has_delayslot(mips_insn)) {
-		pr_info("executing branch insn\n");
-		ret = __compute_return_epc(regs);
-		if (ret < 0)
-			return;
-		task_thread_info(child)->bpt_addr[nsaved++] = regs->cp0_epc;
-	} else {
-		pr_info("executing normal insn\n");
-		task_thread_info(child)->bpt_addr[nsaved++] = pc + 4;
-	}
-
-	/* install breakpoints */
-	for (i = 0; i < nsaved; i++) {
-		ret = read_insn(child, task_thread_info(child)->bpt_addr[i], &insn);
-		if (ret < 0)
-			return;
-
-		task_thread_info(child)->bpt_insn[i] = insn;
-
-		ret = write_insn(child, task_thread_info(child)->bpt_addr[i], BREAKINST);
-		if (ret < 0)
-			return;
-	}
-
-	task_thread_info(child)->bpt_nsaved = nsaved;
-}
-
-static void ptrace_cancel_bpt(struct task_struct *child)
-{
-	int i, nsaved = task_thread_info(child)->bpt_nsaved;
-
-	task_thread_info(child)->bpt_nsaved = 0;
-
-	if (nsaved > 1) {
-		pr_info("%s: bogus nsaved: %d!\n", __func__, nsaved);
-		nsaved = 1;
-	}
-
-	for (i = 0; i < nsaved; i++) {
-		write_insn(child, task_thread_info(child)->bpt_addr[i],
-			  task_thread_info(child)->bpt_insn[i]);
-	}
-}
-
-void user_enable_single_step(struct task_struct *child)
-{
-	set_tsk_thread_flag(child, TIF_SINGLESTEP);
-	ptrace_set_bpt(child);
-}
-
-void user_disable_single_step(struct task_struct *child)
-{
-	clear_tsk_thread_flag(child, TIF_SINGLESTEP);
-	ptrace_cancel_bpt(child);
-}
-
 long arch_ptrace(struct task_struct *child, long request,
 		 unsigned long addr, unsigned long data)
 {

arch/mips/kernel/signal.c

@@ -849,7 +849,7 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 		ret = abi->setup_frame(vdso + abi->vdso->off_sigreturn,
 				       ksig, regs, oldset);
 
-	signal_setup_done(ret, ksig, test_thread_flag(TIF_SINGLESTEP));
+	signal_setup_done(ret, ksig, 0);
 }
 
 static void do_signal(struct pt_regs *regs)