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powerpc/lib/sstep: Fix build errors with newer binutils

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Building tinyconfig with gcc (Debian 11.2.0-16) and assembler (Debian
2.37.90.20220207) the following build error shows up:

  {standard input}: Assembler messages:
  {standard input}:10576: Error: unrecognized opcode: `stbcx.'
  {standard input}:10680: Error: unrecognized opcode: `lharx'
  {standard input}:10694: Error: unrecognized opcode: `lbarx'

Rework to add assembler directives [1] around the instruction.  The
problem with this might be that we can trick a power6 into
single-stepping through an stbcx. for instance, and it will execute that
in kernel mode.

[1] https://sourceware.org/binutils/docs/as/PowerPC_002dPseudo.html#PowerPC_002dPseudo

Fixes: 350779a29f11 ("powerpc: Handle most loads and stores in instruction emulation code")
Cc: stable@vger.kernel.org # v4.14+
Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220224162215.3406642-3-anders.roxell@linaro.org
This commit is contained in:
Anders Roxell 2022-02-24 17:22:15 +01:00 committed by Michael Ellerman
parent 8667d0d64d
commit 8219d31eff
1 changed files with 6 additions and 0 deletions
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6
arch/powerpc/lib/sstep.c
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@ -1089,7 +1089,10 @@ NOKPROBE_SYMBOL(emulate_dcbz);
#define __put_user_asmx(x, addr, err, op, cr) \
__asm__ __volatile__( \
".machine push\n" \
".machine power8\n" \
"1: " op " %2,0,%3\n" \
".machine pop\n" \
" mfcr %1\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
@ -1102,7 +1105,10 @@ NOKPROBE_SYMBOL(emulate_dcbz);
#define __get_user_asmx(x, addr, err, op) \
__asm__ __volatile__( \
".machine push\n" \
".machine power8\n" \
"1: "op" %1,0,%2\n" \
".machine pop\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"3: li %0,%3\n" \