250 lines
8.2 KiB
Diff
250 lines
8.2 KiB
Diff
From: Kyle McMartin <kyle@redhat.com>
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Date: Wed, 5 Apr 2017 17:40:30 +0100
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Subject: [44/62] Add a sysrq option to exit secure boot mode
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Origin: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/commit?id=e26d9e1cb0218082265875505edc284a63385010
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Make sysrq+x exit secure boot mode on x86_64, thereby allowing the running
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kernel image to be modified. This lifts the lockdown.
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Signed-off-by: Kyle McMartin <kyle@redhat.com>
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Signed-off-by: David Howells <dhowells@redhat.com>
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---
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arch/x86/Kconfig | 10 ++++++++++
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arch/x86/kernel/setup.c | 31 +++++++++++++++++++++++++++++++
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drivers/input/misc/uinput.c | 1 +
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drivers/tty/sysrq.c | 19 +++++++++++++------
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include/linux/input.h | 5 +++++
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include/linux/sysrq.h | 8 +++++++-
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kernel/debug/kdb/kdb_main.c | 2 +-
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7 files changed, 68 insertions(+), 8 deletions(-)
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diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
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index 21f39855661d..457c04971849 100644
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--- a/arch/x86/Kconfig
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+++ b/arch/x86/Kconfig
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@@ -1829,6 +1829,16 @@ config EFI_SECURE_BOOT_LOCK_DOWN
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image. Say Y here to automatically lock down the kernel when a
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system boots with UEFI Secure Boot enabled.
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+config EFI_ALLOW_SECURE_BOOT_EXIT
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+ def_bool n
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+ depends on EFI_SECURE_BOOT_LOCK_DOWN && MAGIC_SYSRQ
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+ select ALLOW_LOCKDOWN_LIFT
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+ prompt "Allow secure boot mode to be exited with SysRq+x on a keyboard"
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+ ---help---
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+ Allow secure boot mode to be exited and the kernel lockdown lifted by
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+ typing SysRq+x on a keyboard attached to the system (not permitted
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+ through procfs).
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+
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config SECCOMP
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def_bool y
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prompt "Enable seccomp to safely compute untrusted bytecode"
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diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
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index 85dfa745c442..a415a4817684 100644
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--- a/arch/x86/kernel/setup.c
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+++ b/arch/x86/kernel/setup.c
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@@ -71,6 +71,11 @@
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#include <linux/jiffies.h>
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#include <linux/security.h>
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+#include <linux/fips.h>
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+#include <linux/cred.h>
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+#include <linux/sysrq.h>
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+#include <linux/init_task.h>
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+
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#include <video/edid.h>
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#include <asm/mtrr.h>
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@@ -1330,6 +1335,32 @@ void __init i386_reserve_resources(void)
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#endif /* CONFIG_X86_32 */
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+#ifdef CONFIG_EFI_ALLOW_SECURE_BOOT_EXIT
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+
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+static void sysrq_handle_secure_boot(int key)
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+{
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+ if (!efi_enabled(EFI_SECURE_BOOT))
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+ return;
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+
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+ pr_info("Secure boot disabled\n");
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+ lift_kernel_lockdown();
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+}
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+static struct sysrq_key_op secure_boot_sysrq_op = {
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+ .handler = sysrq_handle_secure_boot,
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+ .help_msg = "unSB(x)",
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+ .action_msg = "Disabling Secure Boot restrictions",
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+ .enable_mask = SYSRQ_DISABLE_USERSPACE,
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+};
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+static int __init secure_boot_sysrq(void)
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+{
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+ if (efi_enabled(EFI_SECURE_BOOT))
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+ register_sysrq_key('x', &secure_boot_sysrq_op);
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+ return 0;
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+}
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+late_initcall(secure_boot_sysrq);
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+#endif /*CONFIG_EFI_ALLOW_SECURE_BOOT_EXIT*/
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+
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+
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static struct notifier_block kernel_offset_notifier = {
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.notifier_call = dump_kernel_offset
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};
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diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
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index 022be0e22eba..4a054a564636 100644
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--- a/drivers/input/misc/uinput.c
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+++ b/drivers/input/misc/uinput.c
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@@ -387,6 +387,7 @@ static int uinput_allocate_device(struct uinput_device *udev)
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if (!udev->dev)
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return -ENOMEM;
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+ udev->dev->flags |= INPUTDEV_FLAGS_SYNTHETIC;
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udev->dev->event = uinput_dev_event;
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input_set_drvdata(udev->dev, udev);
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diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c
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index c6fc7141d7b2..0c96cf60f1a6 100644
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--- a/drivers/tty/sysrq.c
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+++ b/drivers/tty/sysrq.c
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@@ -481,6 +481,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
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/* x: May be registered on mips for TLB dump */
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/* x: May be registered on ppc/powerpc for xmon */
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/* x: May be registered on sparc64 for global PMU dump */
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+ /* x: May be registered on x86_64 for disabling secure boot */
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NULL, /* x */
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/* y: May be registered on sparc64 for global register dump */
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NULL, /* y */
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@@ -524,7 +525,7 @@ static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p)
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sysrq_key_table[i] = op_p;
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}
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-void __handle_sysrq(int key, bool check_mask)
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+void __handle_sysrq(int key, unsigned int from)
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{
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struct sysrq_key_op *op_p;
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int orig_log_level;
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@@ -544,11 +545,15 @@ void __handle_sysrq(int key, bool check_mask)
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op_p = __sysrq_get_key_op(key);
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if (op_p) {
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+ /* Ban synthetic events from some sysrq functionality */
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+ if ((from == SYSRQ_FROM_PROC || from == SYSRQ_FROM_SYNTHETIC) &&
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+ op_p->enable_mask & SYSRQ_DISABLE_USERSPACE)
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+ printk("This sysrq operation is disabled from userspace.\n");
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/*
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* Should we check for enabled operations (/proc/sysrq-trigger
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* should not) and is the invoked operation enabled?
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*/
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- if (!check_mask || sysrq_on_mask(op_p->enable_mask)) {
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+ if (from == SYSRQ_FROM_KERNEL || sysrq_on_mask(op_p->enable_mask)) {
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pr_cont("%s\n", op_p->action_msg);
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console_loglevel = orig_log_level;
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op_p->handler(key);
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@@ -580,7 +585,7 @@ void __handle_sysrq(int key, bool check_mask)
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void handle_sysrq(int key)
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{
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if (sysrq_on())
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- __handle_sysrq(key, true);
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+ __handle_sysrq(key, SYSRQ_FROM_KERNEL);
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}
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EXPORT_SYMBOL(handle_sysrq);
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@@ -661,7 +666,7 @@ static void sysrq_do_reset(unsigned long _state)
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static void sysrq_handle_reset_request(struct sysrq_state *state)
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{
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if (state->reset_requested)
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- __handle_sysrq(sysrq_xlate[KEY_B], false);
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+ __handle_sysrq(sysrq_xlate[KEY_B], SYSRQ_FROM_KERNEL);
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if (sysrq_reset_downtime_ms)
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mod_timer(&state->keyreset_timer,
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@@ -812,8 +817,10 @@ static bool sysrq_handle_keypress(struct sysrq_state *sysrq,
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default:
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if (sysrq->active && value && value != 2) {
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+ int from = sysrq->handle.dev->flags & INPUTDEV_FLAGS_SYNTHETIC ?
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+ SYSRQ_FROM_SYNTHETIC : 0;
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sysrq->need_reinject = false;
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- __handle_sysrq(sysrq_xlate[code], true);
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+ __handle_sysrq(sysrq_xlate[code], from);
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}
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break;
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}
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@@ -1097,7 +1104,7 @@ static ssize_t write_sysrq_trigger(struct file *file, const char __user *buf,
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if (get_user(c, buf))
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return -EFAULT;
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- __handle_sysrq(c, false);
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+ __handle_sysrq(c, SYSRQ_FROM_PROC);
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}
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return count;
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diff --git a/include/linux/input.h b/include/linux/input.h
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index a65e3b24fb18..8b0357175049 100644
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--- a/include/linux/input.h
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+++ b/include/linux/input.h
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@@ -42,6 +42,7 @@ struct input_value {
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* @phys: physical path to the device in the system hierarchy
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* @uniq: unique identification code for the device (if device has it)
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* @id: id of the device (struct input_id)
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+ * @flags: input device flags (SYNTHETIC, etc.)
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* @propbit: bitmap of device properties and quirks
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* @evbit: bitmap of types of events supported by the device (EV_KEY,
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* EV_REL, etc.)
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@@ -124,6 +125,8 @@ struct input_dev {
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const char *uniq;
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struct input_id id;
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+ unsigned int flags;
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+
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unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];
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unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
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@@ -190,6 +193,8 @@ struct input_dev {
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};
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#define to_input_dev(d) container_of(d, struct input_dev, dev)
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+#define INPUTDEV_FLAGS_SYNTHETIC 0x000000001
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+
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/*
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* Verify that we are in sync with input_device_id mod_devicetable.h #defines
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*/
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diff --git a/include/linux/sysrq.h b/include/linux/sysrq.h
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index 387fa7d05c98..f7c52a9ea394 100644
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--- a/include/linux/sysrq.h
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+++ b/include/linux/sysrq.h
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@@ -28,6 +28,8 @@
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#define SYSRQ_ENABLE_BOOT 0x0080
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#define SYSRQ_ENABLE_RTNICE 0x0100
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+#define SYSRQ_DISABLE_USERSPACE 0x00010000
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+
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struct sysrq_key_op {
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void (*handler)(int);
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char *help_msg;
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@@ -42,8 +44,12 @@ struct sysrq_key_op {
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* are available -- else NULL's).
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*/
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+#define SYSRQ_FROM_KERNEL 0x0001
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+#define SYSRQ_FROM_PROC 0x0002
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+#define SYSRQ_FROM_SYNTHETIC 0x0004
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+
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void handle_sysrq(int key);
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-void __handle_sysrq(int key, bool check_mask);
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+void __handle_sysrq(int key, unsigned int from);
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int register_sysrq_key(int key, struct sysrq_key_op *op);
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int unregister_sysrq_key(int key, struct sysrq_key_op *op);
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struct sysrq_key_op *__sysrq_get_key_op(int key);
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diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
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index c8146d53ca67..b480cadf9272 100644
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--- a/kernel/debug/kdb/kdb_main.c
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+++ b/kernel/debug/kdb/kdb_main.c
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@@ -1970,7 +1970,7 @@ static int kdb_sr(int argc, const char **argv)
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return KDB_ARGCOUNT;
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kdb_trap_printk++;
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- __handle_sysrq(*argv[1], check_mask);
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+ __handle_sysrq(*argv[1], check_mask ? SYSRQ_FROM_KERNEL : 0);
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kdb_trap_printk--;
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return 0;
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