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Sat, 3 Mar 2018 19:33:01 -0500 Received: from mail-sn1nam01on0105.outbound.protection.outlook.com ([104.47.32.105]:19488 "EHLO NAM01-SN1-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932667AbeCCW1S (ORCPT ); Sat, 3 Mar 2018 17:27:18 -0500 From: Sasha Levin To: "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" CC: Josh Poimboeuf , Michael Ellerman , Sasha Levin Subject: [PATCH AUTOSEL for 4.15 087/102] powerpc/modules: Don't try to restore r2 after a sibling call Thread-Topic: [PATCH AUTOSEL for 4.15 087/102] powerpc/modules: Don't try to restore r2 after a sibling call Thread-Index: AQHTsz53Oiax7DvYGEy6s5xTlhDpaw== Date: Sat, 3 Mar 2018 22:25:00 +0000 Message-ID: <20180303222318.26006-87-alexander.levin@microsoft.com> References: <20180303222318.26006-1-alexander.levin@microsoft.com> In-Reply-To: <20180303222318.26006-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MW2PR2101MB0970;7:N75chv78qolZnPEzJvirxJMRTjJUwXSnqp/WpE/An4TN8K1f+IPmvBFAJWQRvWO+YiDhxFk808WBCLpmcqbKgMMTKk8YcsjjMspJa2lnvNKsJi+gjgU/aTGkwxJDecm3oXikPNppSmCRf9nCtTQ7u7kcwol+T0ohcaxdtftN6sBTvnyGmgNyokUuta7GXL7silNSaQZeO75uIK0H9nDqNf//9xrU79bn422O1g7MclBlgA1VZpZdtKXtCW2q2Tor x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 560eef2e-c180-4eff-998c-08d58155ea7e x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(48565401081)(5600026)(4604075)(3008032)(2017052603307)(7193020);SRVR:MW2PR2101MB0970; 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x-microsoft-antispam-message-info: hjgTuOrPobhNIekayM/WRwhI7WgcIFQZYXZJ+6np9AUTR8ICjSllvbgYH6ZrDc0lwWUTn2A6hGjceZREla4aqJk33KoUIZisiBhXfD4ykQ9P/nl3if1i7q2nXKVF0vMSlFOgaA9mSTs5KNtmP5c++WE9vP8bqQkIy+1WIt2suGI= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: 560eef2e-c180-4eff-998c-08d58155ea7e X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:25:00.3066 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB0970 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: Josh Poimboeuf [ Upstream commit b9eab08d012fa093947b230f9a87257c27fb829b ] When attempting to load a livepatch module, I got the following error: module_64: patch_module: Expect noop after relocate, got 3c820000 The error was triggered by the following code in unregister_netdevice_queue(): 14c: 00 00 00 48 b 14c 14c: R_PPC64_REL24 net_set_todo 150: 00 00 82 3c addis r4,r2,0 GCC didn't insert a nop after the branch to net_set_todo() because it's a sibling call, so it never returns. The nop isn't needed after the branch in that case. Signed-off-by: Josh Poimboeuf Acked-by: Naveen N. Rao Reviewed-and-tested-by: Kamalesh Babulal Signed-off-by: Michael Ellerman Signed-off-by: Sasha Levin --- arch/powerpc/include/asm/code-patching.h | 1 + arch/powerpc/kernel/module_64.c | 12 +++++++++++- arch/powerpc/lib/code-patching.c | 5 +++++ 3 files changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/includ= e/asm/code-patching.h index abef812de7f8..2c895e8d07f7 100644 --- a/arch/powerpc/include/asm/code-patching.h +++ b/arch/powerpc/include/asm/code-patching.h @@ -33,6 +33,7 @@ int patch_branch(unsigned int *addr, unsigned long target= , int flags); int patch_instruction(unsigned int *addr, unsigned int instr); =20 int instr_is_relative_branch(unsigned int instr); +int instr_is_relative_link_branch(unsigned int instr); int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)= ; unsigned long branch_target(const unsigned int *instr); unsigned int translate_branch(const unsigned int *dest, diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_6= 4.c index 759104b99f9f..180c16f04063 100644 --- a/arch/powerpc/kernel/module_64.c +++ b/arch/powerpc/kernel/module_64.c @@ -487,7 +487,17 @@ static bool is_early_mcount_callsite(u32 *instruction) restore r2. */ static int restore_r2(u32 *instruction, struct module *me) { - if (is_early_mcount_callsite(instruction - 1)) + u32 *prev_insn =3D instruction - 1; + + if (is_early_mcount_callsite(prev_insn)) + return 1; + + /* + * Make sure the branch isn't a sibling call. Sibling calls aren't + * "link" branches and they don't return, so they don't need the r2 + * restore afterwards. + */ + if (!instr_is_relative_link_branch(*prev_insn)) return 1; =20 if (*instruction !=3D PPC_INST_NOP) { diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patch= ing.c index d469224c4ada..096d4e4d31e6 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -302,6 +302,11 @@ int instr_is_relative_branch(unsigned int instr) return instr_is_branch_iform(instr) || instr_is_branch_bform(instr); } =20 +int instr_is_relative_link_branch(unsigned int instr) +{ + return instr_is_relative_branch(instr) && (instr & BRANCH_SET_LINK); +} + static unsigned long branch_iform_target(const unsigned int *instr) { signed long imm; --=20 2.14.1