[PATCHv3 15/17] arm64: uaccess: remove addr_limit_user_check()

Mark Rutland
2020-10-26T13:40:14Z

Now that set_fs() is gone, addr_limit_user_check() is redundant. Remove
the checks and associated thread flag.

To ensure that _TIF_WORK_MASK can be used as an immediate value in an
AND instruction (as it is in `ret_to_user`), TIF_MTE_ASYNC_FAULT is
renumbered to keep the constituent bits of _TIF_WORK_MASK contiguous.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
---
arch/arm64/include/asm/thread_info.h | 6 ++----
arch/arm64/kernel/signal.c | 3 ---
2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 3a88a55de568e..015beafe58f53 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -63,8 +63,7 @@ void arch_release_task_struct(struct task_struct *tsk);
#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */
#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */
#define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */
-#define TIF_FSCHECK 5 /* Check FS is USER_DS on return */
-#define TIF_MTE_ASYNC_FAULT 6 /* MTE Asynchronous Tag Check Fault */
+#define TIF_MTE_ASYNC_FAULT 5 /* MTE Asynchronous Tag Check Fault */
#define TIF_SYSCALL_TRACE 8 /* syscall trace active */
#define TIF_SYSCALL_AUDIT 9 /* syscall auditing */
#define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */
@@ -90,7 +89,6 @@ void arch_release_task_struct(struct task_struct *tsk);
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
#define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU)
#define _TIF_UPROBE (1 << TIF_UPROBE)
-#define _TIF_FSCHECK (1 << TIF_FSCHECK)
#define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP)
#define _TIF_32BIT (1 << TIF_32BIT)
#define _TIF_SVE (1 << TIF_SVE)
@@ -98,7 +96,7 @@ void arch_release_task_struct(struct task_struct *tsk);

#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
_TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
- _TIF_UPROBE | _TIF_FSCHECK | _TIF_MTE_ASYNC_FAULT)
+ _TIF_UPROBE | _TIF_MTE_ASYNC_FAULT)

#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index a8184cad88907..af5c6c6638f7b 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -922,9 +922,6 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
trace_hardirqs_off();

do {
- /* Check valid user FS if needed */
- addr_limit_user_check();
-
if (thread_flags & _TIF_NEED_RESCHED) {
/* Unmask Debug and SError for the next task */
local_daif_restore(DAIF_PROCCTX_NOIRQ);