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Wed, 25 Nov 2020 13:55:14 +0000 (GMT) Received: from [9.77.195.3] (unknown [9.77.195.3]) by d06av24.portsmouth.uk.ibm.com (Postfix) with ESMTP; Wed, 25 Nov 2020 13:55:14 +0000 (GMT) Subject: Re: [PATCH v6 10/22] powerpc/book3s64/pkeys: Store/restore userspace AMR/IAMR correctly on entry and exit from kernel To: Christophe Leroy , linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au References: <20201125051634.509286-1-aneesh.kumar@linux.ibm.com> <20201125051634.509286-11-aneesh.kumar@linux.ibm.com> <5f7a467a-c4c7-76b1-5837-34db0f4db51e@csgroup.eu> From: "Aneesh Kumar K.V" Message-ID: <5a471282-ff4f-cfea-8d30-a0479f0385a1@linux.ibm.com> Date: Wed, 25 Nov 2020 19:25:13 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <5f7a467a-c4c7-76b1-5837-34db0f4db51e@csgroup.eu> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312, 18.0.737 definitions=2020-11-25_08:2020-11-25, 2020-11-25 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 mlxscore=0 clxscore=1015 mlxlogscore=999 spamscore=0 bulkscore=0 lowpriorityscore=0 malwarescore=0 priorityscore=1501 adultscore=0 phishscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011250080 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sandipan Das Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 11/25/20 7:22 PM, Christophe Leroy wrote: > > > Le 25/11/2020 à 06:16, Aneesh Kumar K.V a écrit : >> This prepare kernel to operate with a different value than userspace >> AMR/IAMR. >> For this, AMR/IAMR need to be saved and restored on entry and return >> from the >> kernel. >> >> With KUAP we modify kernel AMR when accessing user address from the >> kernel >> via copy_to/from_user interfaces. We don't need to modify IAMR value in >> similar fashion. >> >> If MMU_FTR_PKEY is enabled we need to save AMR/IAMR in pt_regs on >> entering >> kernel from userspace. If not we can assume that AMR/IAMR is not modified >> from userspace. >> >> We need to save AMR if we have MMU_FTR_KUAP feature enabled and we are >> interrupted within kernel. This is required so that if we get interrupted >> within copy_to/from_user we continue with the right AMR value. >> >> If we hae MMU_FTR_KUEP enabled we need to restore IAMR on return to >> userspace >> beause kernel will be running with a different IAMR value. >> >> Reviewed-by: Sandipan Das >> Signed-off-by: Aneesh Kumar K.V >> --- >> arch/powerpc/include/asm/book3s/64/kup.h | 222 +++++++++++++++++++---- >> arch/powerpc/include/asm/ptrace.h | 5 +- >> arch/powerpc/kernel/asm-offsets.c | 2 + >> arch/powerpc/kernel/entry_64.S | 6 +- >> arch/powerpc/kernel/exceptions-64s.S | 4 +- >> arch/powerpc/kernel/syscall_64.c | 32 +++- >> 6 files changed, 225 insertions(+), 46 deletions(-) >> >> diff --git a/arch/powerpc/include/asm/book3s/64/kup.h >> b/arch/powerpc/include/asm/book3s/64/kup.h >> index 1d38eab83d48..4dbb2d53fd8f 100644 >> --- a/arch/powerpc/include/asm/book3s/64/kup.h >> +++ b/arch/powerpc/include/asm/book3s/64/kup.h >> @@ -13,17 +13,46 @@ >> #ifdef __ASSEMBLY__ >> -.macro kuap_restore_amr gpr1, gpr2 >> -#ifdef CONFIG_PPC_KUAP >> +.macro kuap_restore_user_amr gpr1 >> +#if defined(CONFIG_PPC_PKEY) >> BEGIN_MMU_FTR_SECTION_NESTED(67) >> - mfspr \gpr1, SPRN_AMR >> + /* >> + * AMR and IAMR are going to be different when >> + * returning to userspace. >> + */ >> + ld \gpr1, STACK_REGS_AMR(r1) >> + isync >> + mtspr SPRN_AMR, \gpr1 >> + /* >> + * Restore IAMR only when returning to userspace >> + */ >> + ld \gpr1, STACK_REGS_IAMR(r1) >> + mtspr SPRN_IAMR, \gpr1 >> + >> + /* No isync required, see kuap_restore_user_amr() */ >> + END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_PKEY, 67) >> +#endif >> +.endm >> + >> +.macro kuap_restore_kernel_amr gpr1, gpr2 >> +#if defined(CONFIG_PPC_PKEY) >> + >> + BEGIN_MMU_FTR_SECTION_NESTED(67) >> + /* >> + * AMR is going to be mostly the same since we are >> + * returning to the kernel. Compare and do a mtspr. >> + */ >> ld \gpr2, STACK_REGS_AMR(r1) >> + mfspr \gpr1, SPRN_AMR >> cmpd \gpr1, \gpr2 >> - beq 998f >> + beq 100f >> isync >> mtspr SPRN_AMR, \gpr2 >> - /* No isync required, see kuap_restore_amr() */ >> -998: >> + /* >> + * No isync required, see kuap_restore_amr() >> + * No need to restore IAMR when returning to kernel space. >> + */ >> +100: >> END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUAP, 67) >> #endif >> .endm >> @@ -42,23 +71,98 @@ >> .endm >> #endif >> +/* >> + * if (pkey) { >> + * >> + * save AMR -> stack; >> + * if (kuap) { >> + * if (AMR != BLOCKED) >> + * KUAP_BLOCKED -> AMR; >> + * } >> + * if (from_user) { >> + * save IAMR -> stack; >> + * if (kuep) { >> + * KUEP_BLOCKED ->IAMR >> + * } >> + * } >> + * return; >> + * } >> + * >> + * if (kuap) { >> + * if (from_kernel) { >> + * save AMR -> stack; >> + * if (AMR != BLOCKED) >> + * KUAP_BLOCKED -> AMR; >> + * } >> + * >> + * } >> + */ >> .macro kuap_save_amr_and_lock gpr1, gpr2, use_cr, msr_pr_cr >> -#ifdef CONFIG_PPC_KUAP >> +#if defined(CONFIG_PPC_PKEY) >> + >> + /* >> + * if both pkey and kuap is disabled, nothing to do >> + */ >> + BEGIN_MMU_FTR_SECTION_NESTED(68) >> + b 100f // skip_save_amr >> + END_MMU_FTR_SECTION_NESTED_IFCLR(MMU_FTR_PKEY | MMU_FTR_KUAP, 68) >> + >> + /* >> + * if pkey is disabled and we are entering from userspace >> + * don't do anything. >> + */ >> BEGIN_MMU_FTR_SECTION_NESTED(67) >> .ifnb \msr_pr_cr >> - bne \msr_pr_cr, 99f >> + /* >> + * Without pkey we are not changing AMR outside the kernel >> + * hence skip this completely. >> + */ >> + bne \msr_pr_cr, 100f // from userspace >> .endif >> + END_MMU_FTR_SECTION_NESTED_IFCLR(MMU_FTR_PKEY, 67) >> + >> + /* >> + * pkey is enabled or pkey is disabled but entering from kernel >> + */ >> mfspr \gpr1, SPRN_AMR >> std \gpr1, STACK_REGS_AMR(r1) >> - li \gpr2, (AMR_KUAP_BLOCKED >> AMR_KUAP_SHIFT) >> - sldi \gpr2, \gpr2, AMR_KUAP_SHIFT >> + >> + /* >> + * update kernel AMR with AMR_KUAP_BLOCKED only >> + * if KUAP feature is enabled >> + */ >> + BEGIN_MMU_FTR_SECTION_NESTED(69) >> + LOAD_REG_IMMEDIATE(\gpr2, AMR_KUAP_BLOCKED) >> cmpd \use_cr, \gpr1, \gpr2 >> - beq \use_cr, 99f >> - // We don't isync here because we very recently entered via rfid >> + beq \use_cr, 102f >> + /* >> + * We don't isync here because we very recently entered via an >> interrupt >> + */ >> mtspr SPRN_AMR, \gpr2 >> isync >> -99: >> - END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUAP, 67) >> +102: >> + END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUAP, 69) >> + >> + /* >> + * if entering from kernel we don't need save IAMR >> + */ >> + .ifnb \msr_pr_cr >> + beq \msr_pr_cr, 100f // from kernel space >> + mfspr \gpr1, SPRN_IAMR >> + std \gpr1, STACK_REGS_IAMR(r1) >> + >> + /* >> + * update kernel IAMR with AMR_KUEP_BLOCKED only >> + * if KUEP feature is enabled >> + */ >> + BEGIN_MMU_FTR_SECTION_NESTED(70) >> + LOAD_REG_IMMEDIATE(\gpr2, AMR_KUEP_BLOCKED) >> + mtspr SPRN_IAMR, \gpr2 >> + isync >> + END_MMU_FTR_SECTION_NESTED_IFSET(MMU_FTR_KUEP, 70) >> + .endif >> + >> +100: // skip_save_amr >> #endif >> .endm >> @@ -66,22 +170,42 @@ >> DECLARE_STATIC_KEY_FALSE(uaccess_flush_key); >> -#ifdef CONFIG_PPC_KUAP >> +#ifdef CONFIG_PPC_PKEY >> #include >> #include >> -static inline void kuap_restore_amr(struct pt_regs *regs, unsigned >> long amr) >> +static inline void kuap_restore_user_amr(struct pt_regs *regs) > > While we are at changing the function's names, could we remove the _amr > from the names in order to make it more generic and allow to re-use that > name when we migrate PPC32 to C interrupt/syscall entries/exits ? (see > https://patchwork.ozlabs.org/project/linuxppc-dev/patch/302a0e88e15ce4569d9619631b36248041d5ed27.1586196948.git.christophe.leroy@c-s.fr/) > How do you suggest we rename it? kuap_restore_user is a bit ambiguous right? -aneesh