arm64: sdei: move uaccess logic to arch/arm64/

The SDEI support code is split across arch/arm64/ and drivers/firmware/,
largley this is split so that the arch-specific portions are under
arch/arm64, and the management logic is under drivers/firmware/.
However, exception entry fixups are currently under drivers/firmware.

Let's move the exception entry fixups under arch/arm64/. This
de-clutters the management logic, and puts all the arch-specific
portions in one place. Doing this also allows the fixups to be applied
earlier, so things like PAN and UAO will be in a known good state before
we run other logic. This will also make subsequent refactoring easier.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201202131558.39270-2-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/sdei.c b/arch/arm64/kernel/sdei.c
index 7689f2031c0c41701de66c516fa6773fcec8ead6..4a5f24602aa0cd26fe490ca60888677e1696dba8 100644 (file)
--- a/arch/arm64/kernel/sdei.c
+++ b/arch/arm64/kernel/sdei.c
@@ -178,12 +178,6 @@ static __kprobes unsigned long _sdei_handler(struct pt_regs *regs,
                sdei_api_event_context(i, &regs->regs[i]);
        }
 
-       /*
-        * We didn't take an exception to get here, set PAN. UAO will be cleared
-        * by sdei_event_handler()s force_uaccess_begin() call.
-        */
-       __uaccess_enable_hw_pan();
-
        err = sdei_event_handler(regs, arg);
        if (err)
                return SDEI_EV_FAILED;
@@ -227,6 +221,16 @@ asmlinkage __kprobes notrace unsigned long
 __sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg)
 {
        unsigned long ret;
+       mm_segment_t orig_addr_limit;
+
+       /*
+        * We didn't take an exception to get here, so the HW hasn't set PAN or
+        * cleared UAO, and the exception entry code hasn't reset addr_limit.
+        * Set PAN, then use force_uaccess_begin() to clear UAO and reset
+        * addr_limit.
+        */
+       __uaccess_enable_hw_pan();
+       orig_addr_limit = force_uaccess_begin();
 
        nmi_enter();
 
@@ -234,5 +238,7 @@ __sdei_handler(struct pt_regs *regs, struct sdei_registered_event *arg)
 
        nmi_exit();
 
+       force_uaccess_end(orig_addr_limit);
+
        return ret;
 }

diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
index 840754dcc6ca4429ac17b7e398cc5a8ca70fd6e4..a7e762c352f950d68289e4048eaae657bc031d38 100644 (file)
--- a/drivers/firmware/arm_sdei.c
+++ b/drivers/firmware/arm_sdei.c
@@ -31,7 +31,6 @@
 #include <linux/slab.h>
 #include <linux/smp.h>
 #include <linux/spinlock.h>
-#include <linux/uaccess.h>
 
 /*
  * The call to use to reach the firmware.
@@ -1092,26 +1091,13 @@ int sdei_event_handler(struct pt_regs *regs,
                       struct sdei_registered_event *arg)
 {
        int err;
-       mm_segment_t orig_addr_limit;
        u32 event_num = arg->event_num;
 
-       /*
-        * Save restore 'fs'.
-        * The architecture's entry code save/restores 'fs' when taking an
-        * exception from the kernel. This ensures addr_limit isn't inherited
-        * if you interrupted something that allowed the uaccess routines to
-        * access kernel memory.
-        * Do the same here because this doesn't come via the same entry code.
-       */
-       orig_addr_limit = force_uaccess_begin();
-
        err = arg->callback(event_num, regs, arg->callback_arg);
        if (err)
                pr_err_ratelimited("event %u on CPU %u failed with error: %d\n",
                                   event_num, smp_processor_id(), err);
 
-       force_uaccess_end(orig_addr_limit);
-
        return err;
 }
 NOKPROBE_SYMBOL(sdei_event_handler);