releases/4.9.163/arm-8781-1-fix-thumb-2-syscall-return-for-binutils-2.patch

   1 From a828b79637a2608b9872e1a283ef12436dce0fc4 Mon Sep 17 00:00:00 2001
   2 From: Vincent Whitchurch <vincent.whitchurch@axis.com>
   3 Date: Fri, 13 Jul 2018 11:12:22 +0100
   4 Subject: ARM: 8781/1: Fix Thumb-2 syscall return for binutils 2.29+
   5
   6 [ Upstream commit afc9f65e01cd114cb2cedf544d22239116ce0cc6 ]
   7
   8 When building the kernel as Thumb-2 with binutils 2.29 or newer, if the
   9 assembler has seen the .type directive (via ENDPROC()) for a symbol, it
  10 automatically handles the setting of the lowest bit when the symbol is
  11 used with ADR.  The badr macro on the other hand handles this lowest bit
  12 manually.  This leads to a jump to a wrong address in the wrong state
  13 in the syscall return path:
  14
  15  Internal error: Oops - undefined instruction: 0 [#2] SMP THUMB2
  16  Modules linked in:
  17  CPU: 0 PID: 652 Comm: modprobe Tainted: G      D           4.18.0-rc3+ #8
  18  PC is at ret_fast_syscall+0x4/0x62
  19  LR is at sys_brk+0x109/0x128
  20  pc : [<80101004>]    lr : [<801c8a35>]    psr: 60000013
  21  Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
  22  Control: 50c5387d  Table: 9e82006a  DAC: 00000051
  23  Process modprobe (pid: 652, stack limit = 0x(ptrval))
  24
  25  80101000 <ret_fast_syscall>:
  26  80101000:       b672            cpsid   i
  27  80101002:       f8d9 2008       ldr.w   r2, [r9, #8]
  28  80101006:       f1b2 4ffe       cmp.w   r2, #2130706432 ; 0x7f000000
  29
  30  80101184 <local_restart>:
  31  80101184:       f8d9 a000       ldr.w   sl, [r9]
  32  80101188:       e92d 0030       stmdb   sp!, {r4, r5}
  33  8010118c:       f01a 0ff0       tst.w   sl, #240        ; 0xf0
  34  80101190:       d117            bne.n   801011c2 <__sys_trace>
  35  80101192:       46ba            mov     sl, r7
  36  80101194:       f5ba 7fc8       cmp.w   sl, #400        ; 0x190
  37  80101198:       bf28            it      cs
  38  8010119a:       f04f 0a00       movcs.w sl, #0
  39  8010119e:       f3af 8014       nop.w   {20}
  40  801011a2:       f2af 1ea2       subw    lr, pc, #418    ; 0x1a2
  41
  42 To fix this, add a new symbol name which doesn't have ENDPROC used on it
  43 and use that with badr.  We can't remove the badr usage since that would
  44 would cause breakage with older binutils.
  45
  46 Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
  47 Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
  48 Signed-off-by: Sasha Levin <sashal@kernel.org>
  49 ---
  50  arch/arm/kernel/entry-common.S |    4 +++-
  51  1 file changed, 3 insertions(+), 1 deletion(-)
  52
  53 --- a/arch/arm/kernel/entry-common.S
  54 +++ b/arch/arm/kernel/entry-common.S
  55 @@ -32,6 +32,7 @@
  56   * features make this path too inefficient.
  57   */
  58  ret_fast_syscall:
  59 +__ret_fast_syscall:
  60   UNWIND(.fnstart       )
  61   UNWIND(.cantunwind    )
  62         disable_irq_notrace                     @ disable interrupts
  63 @@ -57,6 +58,7 @@ fast_work_pending:
  64   * r0 first to avoid needing to save registers around each C function call.
  65   */
  66  ret_fast_syscall:
  67 +__ret_fast_syscall:
  68   UNWIND(.fnstart       )
  69   UNWIND(.cantunwind    )
  70         str     r0, [sp, #S_R0 + S_OFF]!        @ save returned r0
  71 @@ -223,7 +225,7 @@ local_restart:
  72         tst     r10, #_TIF_SYSCALL_WORK         @ are we tracing syscalls?
  73         bne     __sys_trace
  74
  75 -       invoke_syscall tbl, scno, r10, ret_fast_syscall
  76 +       invoke_syscall tbl, scno, r10, __ret_fast_syscall
  77
  78         add     r1, sp, #S_OFF
  79  2:     cmp     scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)