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

---
 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