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Subject[PATCH v5 7/14] x86 support for Uprobes
uprobes_x86.patch

From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

X86 support for Uprobes

This patch provides x86 specific details for uprobes.
This includes interrupt notifier for uprobes, enabling/disabling
singlestep.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
---
arch/x86/Kconfig | 1 +
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/signal.c | 12 +++++++
arch/x86/kernel/uprobes.c | 77 +++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 91 insertions(+), 0 deletions(-)
create mode 100644 arch/x86/kernel/uprobes.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index db1b378..a2bf479 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -55,6 +55,7 @@ config X86
select HAVE_HW_BREAKPOINT
select HAVE_MIXED_BREAKPOINTS_REGS
select HAVE_USER_BKPT
+ select HAVE_UPROBES
select PERF_EVENTS
select HAVE_PERF_EVENTS_NMI
select ANON_INODES
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 53cf2af..e2c4262 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -116,6 +116,7 @@ obj-$(CONFIG_X86_CHECK_BIOS_CORRUPTION) += check.o
obj-$(CONFIG_SWIOTLB) += pci-swiotlb.o

obj-$(CONFIG_USER_BKPT) += user_bkpt.o
+obj-$(CONFIG_UPROBES) += uprobes.o

###
# 64 bit specific files
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 851bc8d..dde9a42 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -850,7 +850,19 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)

if (thread_info_flags & _TIF_UPROBE) {
clear_thread_flag(TIF_UPROBE);
+#ifdef CONFIG_X86_32
+ /*
+ * On x86_32, do_notify_resume() gets called with
+ * interrupts disabled. Hence enable interrupts if they
+ * are still disabled.
+ */
+ native_irq_enable();
+#endif
uprobe_notify_resume(regs);
+
+#ifdef CONFIG_X86_32
+ native_irq_disable();
+#endif
}

if (thread_info_flags & _TIF_NOTIFY_RESUME) {
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
new file mode 100644
index 0000000..5643b96
--- /dev/null
+++ b/arch/x86/kernel/uprobes.c
@@ -0,0 +1,77 @@
+/*
+ * Userspace Probes (UProbes)
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2010
+ * Authors:
+ * Srikar Dronamraju
+ * Ananth N Mavinakayanahalli
+ */
+
+#include <linux/sched.h>
+#include <linux/kdebug.h>
+#include <linux/uprobes.h>
+
+/*
+ * Wrapper routine for handling exceptions.
+ */
+int uprobes_exception_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ struct die_args *args = data;
+ struct pt_regs *regs = args->regs;
+ int ret = NOTIFY_DONE;
+
+ /* We are only interested in userspace traps */
+ if (regs && !user_mode_vm(regs))
+ return NOTIFY_DONE;
+
+ switch (val) {
+ case DIE_INT3:
+ /* Run your handler here */
+ if (uprobe_bkpt_notifier(regs))
+ ret = NOTIFY_STOP;
+ break;
+ case DIE_DEBUG:
+ if (uprobe_post_notifier(regs))
+ ret = NOTIFY_STOP;
+ default:
+ break;
+ }
+ return ret;
+}
+
+void arch_uprobe_enable_sstep(struct pt_regs *regs)
+{
+ /*
+ * Enable single-stepping by
+ * - Set TF on stack
+ * - Set TIF_SINGLESTEP: Guarantees that TF is set when
+ * returning to user mode.
+ * - Indicate that TF is set by us.
+ */
+ regs->flags |= X86_EFLAGS_TF;
+ set_thread_flag(TIF_SINGLESTEP);
+ set_thread_flag(TIF_FORCED_TF);
+}
+
+void arch_uprobe_disable_sstep(struct pt_regs *regs)
+{
+ /* Disable single-stepping by clearing what we set */
+ clear_thread_flag(TIF_SINGLESTEP);
+ clear_thread_flag(TIF_FORCED_TF);
+ regs->flags &= ~X86_EFLAGS_TF;
+}

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