powerpc/fault: Perform exception fixup in do_page_fault()

Exception fixup doesn't require the heady full regs saving,
do it from do_page_fault() directly.

For that, split bad_page_fault() in two parts.

As bad_page_fault() can also be called from other places than
handle_page_fault(), it will still perform exception fixup and
fallback on __bad_page_fault().

handle_page_fault() directly calls __bad_page_fault() as the
exception fixup will now be done by do_page_fault()

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/bd07d6fef9237614cd6d318d8f19faeeadaa816b.1607491748.git.christophe.leroy@csgroup.eu

diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index ba0500872cce0bb8c0176c044972e88a9fc20329..464f8ca8a5c970ec06f7f034391baf7fda27acc5 100644 (file)
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -113,6 +113,7 @@
 struct pt_regs;
 extern int do_page_fault(struct pt_regs *, unsigned long, unsigned long);
 extern void bad_page_fault(struct pt_regs *, unsigned long, int);
+void __bad_page_fault(struct pt_regs *regs, unsigned long address, int sig);
 extern void _exception(int, struct pt_regs *, int, unsigned long);
 extern void _exception_pkey(struct pt_regs *, unsigned long, int);
 extern void die(const char *, struct pt_regs *, long);

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 58177c71dfd4b3fbf6122163ae1ba5cd369f6699..1c9b0ccc2172e8480da768e953550f57b83dfd24 100644 (file)
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -684,7 +684,7 @@ handle_page_fault:
        mr      r5,r3
        addi    r3,r1,STACK_FRAME_OVERHEAD
        lwz     r4,_DAR(r1)
-       bl      bad_page_fault
+       bl      __bad_page_fault
        b       ret_from_except_full
 
 #ifdef CONFIG_PPC_BOOK3S_32

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index f579ce46eef2d509e90d64256b5114e53eecb5c1..74d07dc0bb48d166175923bf1418d6325b09df45 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -1023,7 +1023,7 @@ storage_fault_common:
        mr      r5,r3
        addi    r3,r1,STACK_FRAME_OVERHEAD
        ld      r4,_DAR(r1)
-       bl      bad_page_fault
+       bl      __bad_page_fault
        b       ret_from_except
 
 /*

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 1c8f1b90e1746e11fef171889bd67b56d063adc1..e02ad6fefa46cc4232199fddac38353c5433246b 100644 (file)
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -3259,7 +3259,7 @@ handle_page_fault:
        mr      r5,r3
        addi    r3,r1,STACK_FRAME_OVERHEAD
        ld      r4,_DAR(r1)
-       bl      bad_page_fault
+       bl      __bad_page_fault
        b       interrupt_return
 
 /* We have a data breakpoint exception - handle it */

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 389a2a87526298d1a547b97581a03abae1d57348..8961b44f350cd66480905e33dcc753337cf467f6 100644 (file)
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -545,10 +545,20 @@ NOKPROBE_SYMBOL(__do_page_fault);
 int do_page_fault(struct pt_regs *regs, unsigned long address,
                  unsigned long error_code)
 {
+       const struct exception_table_entry *entry;
        enum ctx_state prev_state = exception_enter();
        int rc = __do_page_fault(regs, address, error_code);
        exception_exit(prev_state);
-       return rc;
+       if (likely(!rc))
+               return 0;
+
+       entry = search_exception_tables(regs->nip);
+       if (unlikely(!entry))
+               return rc;
+
+       instruction_pointer_set(regs, extable_fixup(entry));
+
+       return 0;
 }
 NOKPROBE_SYMBOL(do_page_fault);
 
@@ -557,17 +567,10 @@ NOKPROBE_SYMBOL(do_page_fault);
  * It is called from the DSI and ISI handlers in head.S and from some
  * of the procedures in traps.c.
  */
-void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
+void __bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 {
-       const struct exception_table_entry *entry;
        int is_write = page_fault_is_write(regs->dsisr);
 
-       /* Are we prepared to handle this fault?  */
-       if ((entry = search_exception_tables(regs->nip)) != NULL) {
-               regs->nip = extable_fixup(entry);
-               return;
-       }
-
        /* kernel has accessed a bad area */
 
        switch (TRAP(regs)) {
@@ -601,3 +604,15 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
 
        die("Kernel access of bad area", regs, sig);
 }
+
+void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
+{
+       const struct exception_table_entry *entry;
+
+       /* Are we prepared to handle this fault?  */
+       entry = search_exception_tables(instruction_pointer(regs));
+       if (entry)
+               instruction_pointer_set(regs, extable_fixup(entry));
+       else
+               __bad_page_fault(regs, address, sig);
+}