OpenRISC: PTrace

This patch implements minimal PTrace support.  The pt_regs structure is
not exported to userspace for OpenRISC; rather, the GETREGSET mechanism
is intended to be used and the registers, as such, exported in the core
dump format which is ABI stable.  This is in line with what is intended
for new architectures as of 2.6.34 and has the advantage of permitting
the layout of the registers on the kernel stack (as per pt_regs) to be
freely modified.

Signed-off-by: Jonas Bonn <jonas@southpole.se>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 211 insertions, 0 deletions

diff --git a/arch/openrisc/kernel/ptrace.c b/arch/openrisc/kernel/ptrace.c
new file mode 100644
index 000000000000..656b94beab89
--- /dev/null
+++ b/arch/openrisc/kernel/ptrace.c
@@ -0,0 +1,211 @@
+/*
+ * OpenRISC ptrace.c
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
+ * Copyright (C) 2005 Gyorgy Jeney <nog@bsemi.com>
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ */
+
+#include <stddef.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/string.h>
+
+#include <linux/mm.h>
+#include <linux/errno.h>
+#include <linux/ptrace.h>
+#include <linux/audit.h>
+#include <linux/regset.h>
+#include <linux/tracehook.h>
+#include <linux/elf.h>
+
+#include <asm/thread_info.h>
+#include <asm/segment.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/system.h>
+
+/*
+ * Copy the thread state to a regset that can be interpreted by userspace.
+ *
+ * It doesn't matter what our internal pt_regs structure looks like.  The
+ * important thing is that we export a consistent view of the thread state
+ * to userspace.  As such, we need to make sure that the regset remains
+ * ABI compatible as defined by the struct user_regs_struct:
+ *
+ * (Each item is a 32-bit word)
+ * r0 = 0 (exported for clarity)
+ * 31 GPRS r1-r31
+ * PC (Program counter)
+ * SR (Supervision register)
+ */
+static int genregs_get(struct task_struct *target,
+                       const struct user_regset *regset,
+                       unsigned int pos, unsigned int count,
+                       void *kbuf, void __user * ubuf)
+{
+        const struct pt_regs *regs = task_pt_regs(target);
+        int ret;
+
+        /* r0 */
+        ret = user_regset_copyout_zero(&pos, &count, &kbuf, &ubuf, 0, 4);
+
+        if (!ret)
+                ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+                                          regs->gpr+1, 4, 4*32);
+        if (!ret)
+                ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+                                  &regs->pc, 4*32, 4*33);
+        if (!ret)
+                ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
+                                          &regs->sr, 4*33, 4*34);
+        if (!ret)
+                ret = user_regset_copyout_zero(&pos, &count, &kbuf, &ubuf,
+                                               4*34, -1);
+
+        return ret;
+}
+
+/*
+ * Set the thread state from a regset passed in via ptrace
+ */
+static int genregs_set(struct task_struct *target,
+                       const struct user_regset *regset,
+                       unsigned int pos, unsigned int count,
+                       const void *kbuf, const void __user * ubuf)
+{
+        struct pt_regs *regs = task_pt_regs(target);
+        int ret;
+
+        /* ignore r0 */
+        ret = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf, 0, 4);
+        /* r1 - r31 */
+        if (!ret)
+                ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+                                         regs->gpr+1, 4, 4*32);
+        /* PC */
+        if (!ret)
+                ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+                                 &regs->pc, 4*32, 4*33);
+        /*
+         * Skip SR and padding... userspace isn't allowed to changes bits in
+         * the Supervision register
+         */
+        if (!ret)
+                ret = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf,
+                                                4*33, -1);
+
+        return ret;
+}
+
+/*
+ * Define the register sets available on OpenRISC under Linux
+ */
+enum or1k_regset {
+        REGSET_GENERAL,
+};
+
+static const struct user_regset or1k_regsets[] = {
+        [REGSET_GENERAL] = {
+                            .core_note_type = NT_PRSTATUS,
+                            .n = ELF_NGREG,
+                            .size = sizeof(long),
+                            .align = sizeof(long),
+                            .get = genregs_get,
+                            .set = genregs_set,
+                            },
+};
+
+static const struct user_regset_view user_or1k_native_view = {
+        .name = "or1k",
+        .e_machine = EM_OPENRISC,
+        .regsets = or1k_regsets,
+        .n = ARRAY_SIZE(or1k_regsets),
+};
+
+const struct user_regset_view *task_user_regset_view(struct task_struct *task)
+{
+        return &user_or1k_native_view;
+}
+
+/*
+ * does not yet catch signals sent when the child dies.
+ * in exit.c or in signal.c.
+ */
+
+
+/*
+ * Called by kernel/ptrace.c when detaching..
+ *
+ * Make sure the single step bit is not set.
+ */
+void ptrace_disable(struct task_struct *child)
+{
+        pr_debug("ptrace_disable(): TODO\n");
+
+        user_disable_single_step(child);
+        clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+}
+
+long arch_ptrace(struct task_struct *child, long request, unsigned long addr,
+                 unsigned long data)
+{
+        int ret;
+
+        switch (request) {
+        default:
+                ret = ptrace_request(child, request, addr, data);
+                break;
+        }
+
+        return ret;
+}
+
+/*
+ * Notification of system call entry/exit
+ * - triggered by current->work.syscall_trace
+ */
+asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
+{
+        long ret = 0;
+
+        if (test_thread_flag(TIF_SYSCALL_TRACE) &&
+            tracehook_report_syscall_entry(regs))
+                /*
+                 * Tracing decided this syscall should not happen.
+                 * We'll return a bogus call number to get an ENOSYS
+                 * error, but leave the original number in <something>.
+                 */
+                ret = -1L;
+
+        /* Are these regs right??? */
+        if (unlikely(current->audit_context))
+                audit_syscall_entry(audit_arch(), regs->syscallno,
+                                    regs->gpr[3], regs->gpr[4],
+                                    regs->gpr[5], regs->gpr[6]);
+
+        return ret ? : regs->syscallno;
+}
+
+asmlinkage void do_syscall_trace_leave(struct pt_regs *regs)
+{
+        int step;
+
+        if (unlikely(current->audit_context))
+                audit_syscall_exit(AUDITSC_RESULT(regs->gpr[11]),
+                                   regs->gpr[11]);
+
+        step = test_thread_flag(TIF_SINGLESTEP);
+        if (step || test_thread_flag(TIF_SYSCALL_TRACE))
+                tracehook_report_syscall_exit(regs, step);
+}