linux-kernel - [PATCH 4.19 35/58] powerpc/lib/sstep: fix ptesync build error

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Message-Id: <20220221084913.013621444@linuxfoundation.org>
Date:   Mon, 21 Feb 2022 09:49:28 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Anders Roxell <anders.roxell@...aro.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: [PATCH 4.19 35/58] powerpc/lib/sstep: fix ptesync build error

From: Anders Roxell <anders.roxell@...aro.org>

commit fe663df7825811358531dc2e8a52d9eaa5e3515e upstream.

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}:2088: Error: unrecognized opcode: `ptesync'
  make[3]: *** [/builds/linux/scripts/Makefile.build:287: arch/powerpc/lib/sstep.o] Error 1

Add the 'ifdef CONFIG_PPC64' around the 'ptesync' in function
'emulate_update_regs()' to like it is in 'analyse_instr()'. Since it looks like
it got dropped inadvertently by commit 3cdfcbfd32b9 ("powerpc: Change
analyse_instr so it doesn't modify *regs").

A key detail is that analyse_instr() will never recognise lwsync or
ptesync on 32-bit (because of the existing ifdef), and as a result
emulate_update_regs() should never be called with an op specifying
either of those on 32-bit. So removing them from emulate_update_regs()
should be a nop in terms of runtime behaviour.

Fixes: 3cdfcbfd32b9 ("powerpc: Change analyse_instr so it doesn't modify *regs")
Cc: stable@...r.kernel.org # v4.14+
Suggested-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Anders Roxell <anders.roxell@...aro.org>
[mpe: Add last paragraph of change log mentioning analyse_instr() details]
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/r/20220211005113.1361436-1-anders.roxell@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/powerpc/lib/sstep.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/powerpc/lib/sstep.c
+++ b/arch/powerpc/lib/sstep.c
@@ -2681,12 +2681,14 @@ void emulate_update_regs(struct pt_regs
 		case BARRIER_EIEIO:
 			eieio();
 			break;
+#ifdef CONFIG_PPC64
 		case BARRIER_LWSYNC:
 			asm volatile("lwsync" : : : "memory");
 			break;
 		case BARRIER_PTESYNC:
 			asm volatile("ptesync" : : : "memory");
 			break;
+#endif
 		}
 		break;