[PATCH v3 4/6] uaccess-buffer: add CONFIG_GENERIC_ENTRY support

[Peter Collingbourne]

Add uaccess logging support on architectures that use
CONFIG_GENERIC_ENTRY (currently only s390 and x86).

Link: https://linux-review.googlesource.com/id/I3c5eb19a7e4a1dbe6095f6971f7826c4b0663f7d
Signed-off-by: Peter Collingbourne <pcc at google.com>
---
 arch/Kconfig                 |  6 ++++++
 include/linux/entry-common.h |  2 ++
 include/linux/thread_info.h  |  4 ++++
 kernel/entry/common.c        | 10 ++++++++++
 4 files changed, 22 insertions(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index d3c4ab249e9c..c4dcab5279ac 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -31,6 +31,7 @@ config HOTPLUG_SMT
 	bool
 
 config GENERIC_ENTRY
+       select HAVE_ARCH_UACCESS_BUFFER
        bool
 
 config KPROBES
@@ -1312,6 +1313,11 @@ config ARCH_HAS_PARANOID_L1D_FLUSH
 config DYNAMIC_SIGFRAME
 	bool
 
+config HAVE_ARCH_UACCESS_BUFFER
+	bool
+	help
+	  Select if the architecture's syscall entry/exit code supports uaccess buffers.
+
 source "kernel/gcov/Kconfig"
 
 source "scripts/gcc-plugins/Kconfig"
diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
index 2e2b8d6140ed..973fcd1d48a3 100644
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -42,12 +42,14 @@
 				 SYSCALL_WORK_SYSCALL_EMU |		\
 				 SYSCALL_WORK_SYSCALL_AUDIT |		\
 				 SYSCALL_WORK_SYSCALL_USER_DISPATCH |	\
+				 SYSCALL_WORK_UACCESS_BUFFER_ENTRY |	\
 				 ARCH_SYSCALL_WORK_ENTER)
 #define SYSCALL_WORK_EXIT	(SYSCALL_WORK_SYSCALL_TRACEPOINT |	\
 				 SYSCALL_WORK_SYSCALL_TRACE |		\
 				 SYSCALL_WORK_SYSCALL_AUDIT |		\
 				 SYSCALL_WORK_SYSCALL_USER_DISPATCH |	\
 				 SYSCALL_WORK_SYSCALL_EXIT_TRAP	|	\
+				 SYSCALL_WORK_UACCESS_BUFFER_EXIT |	\
 				 ARCH_SYSCALL_WORK_EXIT)
 
 /*
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index ad0c4e041030..b0f8ea86967f 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -46,6 +46,8 @@ enum syscall_work_bit {
 	SYSCALL_WORK_BIT_SYSCALL_AUDIT,
 	SYSCALL_WORK_BIT_SYSCALL_USER_DISPATCH,
 	SYSCALL_WORK_BIT_SYSCALL_EXIT_TRAP,
+	SYSCALL_WORK_BIT_UACCESS_BUFFER_ENTRY,
+	SYSCALL_WORK_BIT_UACCESS_BUFFER_EXIT,
 };
 
 #define SYSCALL_WORK_SECCOMP		BIT(SYSCALL_WORK_BIT_SECCOMP)
@@ -55,6 +57,8 @@ enum syscall_work_bit {
 #define SYSCALL_WORK_SYSCALL_AUDIT	BIT(SYSCALL_WORK_BIT_SYSCALL_AUDIT)
 #define SYSCALL_WORK_SYSCALL_USER_DISPATCH BIT(SYSCALL_WORK_BIT_SYSCALL_USER_DISPATCH)
 #define SYSCALL_WORK_SYSCALL_EXIT_TRAP	BIT(SYSCALL_WORK_BIT_SYSCALL_EXIT_TRAP)
+#define SYSCALL_WORK_UACCESS_BUFFER_ENTRY	BIT(SYSCALL_WORK_BIT_UACCESS_BUFFER_ENTRY)
+#define SYSCALL_WORK_UACCESS_BUFFER_EXIT	BIT(SYSCALL_WORK_BIT_UACCESS_BUFFER_EXIT)
 #endif
 
 #include <asm/thread_info.h>
diff --git a/kernel/entry/common.c b/kernel/entry/common.c
index d5a61d565ad5..57c4bb01a554 100644
--- a/kernel/entry/common.c
+++ b/kernel/entry/common.c
@@ -6,6 +6,7 @@
 #include <linux/livepatch.h>
 #include <linux/audit.h>
 #include <linux/tick.h>
+#include <linux/uaccess-buffer.h>
 
 #include "common.h"
 
@@ -70,6 +71,9 @@ static long syscall_trace_enter(struct pt_regs *regs, long syscall,
 			return ret;
 	}
 
+	if (work & SYSCALL_WORK_UACCESS_BUFFER_ENTRY)
+		uaccess_buffer_syscall_entry();
+
 	/* Either of the above might have changed the syscall number */
 	syscall = syscall_get_nr(current, regs);
 
@@ -197,14 +201,17 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs,
 static void exit_to_user_mode_prepare(struct pt_regs *regs)
 {
 	unsigned long ti_work = READ_ONCE(current_thread_info()->flags);
+	bool uaccess_buffer_pending;
 
 	lockdep_assert_irqs_disabled();
 
 	/* Flush pending rcuog wakeup before the last need_resched() check */
 	tick_nohz_user_enter_prepare();
 
+	uaccess_buffer_pending = uaccess_buffer_pre_exit_loop();
 	if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK))
 		ti_work = exit_to_user_mode_loop(regs, ti_work);
+	uaccess_buffer_post_exit_loop(uaccess_buffer_pending);
 
 	arch_exit_to_user_mode_prepare(regs, ti_work);
 
@@ -247,6 +254,9 @@ static void syscall_exit_work(struct pt_regs *regs, unsigned long work)
 
 	audit_syscall_exit(regs);
 
+	if (work & SYSCALL_WORK_UACCESS_BUFFER_EXIT)
+		uaccess_buffer_syscall_exit();
+
 	if (work & SYSCALL_WORK_SYSCALL_TRACEPOINT)
 		trace_sys_exit(regs, syscall_get_return_value(current, regs));
 
-- 
2.34.1.173.g76aa8bc2d0-goog