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Wed, 08 Apr 2020 05:05:22 +0000 Received: from abhmp0012.oracle.com (abhmp0012.oracle.com [141.146.116.18]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 03855LAJ022165; Wed, 8 Apr 2020 05:05:21 GMT Received: from monad.ca.oracle.com (/10.156.75.81) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 07 Apr 2020 22:05:21 -0700 From: Ankur Arora To: linux-kernel@vger.kernel.org, x86@kernel.org Subject: [RFC PATCH 16/26] x86/alternatives: Add paravirt patching at runtime Date: Tue, 7 Apr 2020 22:03:13 -0700 Message-Id: <20200408050323.4237-17-ankur.a.arora@oracle.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200408050323.4237-1-ankur.a.arora@oracle.com> References: <20200408050323.4237-1-ankur.a.arora@oracle.com> MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9584 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 suspectscore=0 bulkscore=0 mlxlogscore=999 mlxscore=0 phishscore=0 malwarescore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004080037 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9584 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 mlxlogscore=999 mlxscore=0 priorityscore=1501 bulkscore=0 adultscore=0 impostorscore=0 phishscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004080037 X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: jgross@suse.com, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, peterz@infradead.org, hpa@zytor.com, Ankur Arora , virtualization@lists.linux-foundation.org, pbonzini@redhat.com, namit@vmware.com, mhiramat@kernel.org, jpoimboe@redhat.com, mihai.carabas@oracle.com, bp@alien8.de, vkuznets@redhat.com, boris.ostrovsky@oracle.com Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" Add paravirt_patch_runtime() which uses text_poke_late() to patch paravirt sites. Also add paravirt_worker() which does the actual insn generation generate_paravirt() (which uses runtime_patch() to generate the appropriate native or paravirt insn sequences) and then calls text_poke_site() to do the actual poking. CPU0 CPUx ---- ---- patch_worker() patch_worker() /* Traversal, insn-gen */ text_poke_sync_finish() tps.patch_worker() /* = paravirt_worker() */ /* * wait until: /* for each patch-site */ * tps->state == PATCH_DONE generate_paravirt() */ runtime_patch() text_poke_site() poke_sync() ... ... smp_store_release(&tps->state, PATCH_DONE) Signed-off-by: Ankur Arora --- arch/x86/include/asm/text-patching.h | 2 + arch/x86/kernel/alternative.c | 98 +++++++++++++++++++++++++++- 2 files changed, 99 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/text-patching.h b/arch/x86/include/asm/text-patching.h index c4b2814f2f9d..e86709a8287e 100644 --- a/arch/x86/include/asm/text-patching.h +++ b/arch/x86/include/asm/text-patching.h @@ -21,6 +21,8 @@ static inline void apply_paravirt(struct paravirt_patch_site *start, #ifndef CONFIG_PARAVIRT_RUNTIME #define __parainstructions_runtime NULL #define __parainstructions_runtime_end NULL +#else +int paravirt_runtime_patch(void); #endif /* diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 452d4081eded..1c5acdc4f349 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1463,7 +1463,9 @@ static void poke_sync(struct text_poke_state *tps, int state, int offset, /** * text_poke_site() - called on the primary to patch a single call site. * - * Returns after switching tps->state to PATCH_SYNC_DONE. + * Called in thread context with tps->state == PATCH_SYNC_DONE where it + * takes tps->state through different PATCH_SYNC_* states, returning + * after having switched the tps->state back to PATCH_SYNC_DONE. */ static void __maybe_unused text_poke_site(struct text_poke_state *tps, struct text_poke_loc *tp) @@ -1598,6 +1600,16 @@ static int __maybe_unused text_poke_late(patch_worker_t worker, void *stage) return ret; } +/* + * Check if this address is still in scope of this module's .text section. + */ +static bool __maybe_unused stale_address(struct alt_module *am, u8 *p) +{ + if (p < am->text || p >= am->text_end) + return true; + return false; +} + #ifdef CONFIG_PARAVIRT_RUNTIME struct paravirt_stage_entry { void *dest; /* pv_op destination */ @@ -1654,4 +1666,88 @@ void text_poke_pv_stage_zero(void) lockdep_assert_held(&text_mutex); pv_stage.count = 0; } + +/** + * generate_paravirt - fill up the insn sequence for a pv-op. + * + * @tp - address of struct text_poke_loc + * @op - the pv-op entry for this location + * @site - patch site (kernel or module text) + */ +static void generate_paravirt(struct text_poke_loc *tp, + struct paravirt_stage_entry *op, + struct paravirt_patch_site *site) +{ + unsigned int used; + + BUG_ON(site->len > POKE_MAX_OPCODE_SIZE); + + text_poke_loc_init(tp, site->instr, site->instr, site->len, NULL, true); + + /* + * Paravirt patches can patch calls (ex. mmu.tlb_flush), + * callee_saves(ex. queued_spin_unlock). + * + * runtime_patch() calls native_patch(), or paravirt_patch() + * based on the destination. + */ + used = runtime_patch(site->type, (void *)tp->text, op->dest, + (unsigned long)site->instr, site->len); + + /* No good way to recover. */ + BUG_ON(used < 0); + + /* Pad the rest with nops */ + add_nops((void *)tp->text + used, site->len - used); +} + +/** + * paravirt_worker - generate the paravirt patching + * insns and calls text_poke_site() to do the actual patching. + */ +static void paravirt_worker(struct text_poke_state *tps) +{ + struct paravirt_patch_site *site; + struct paravirt_stage *stage = tps->stage; + struct paravirt_stage_entry *op = &stage->ops[0]; + struct alt_module *am; + struct text_poke_loc tp; + int i; + + list_for_each_entry(am, tps->head, next) { + for (site = am->para; site < am->para_end; site++) { + if (stale_address(am, site->instr)) + continue; + + for (i = 0; i < stage->count; i++) { + if (op[i].type != site->type) + continue; + + generate_paravirt(&tp, &op[i], site); + + text_poke_site(tps, &tp); + } + } + } +} + +/** + * paravirt_runtime_patch() -- patch pv-ops, including paired ops. + * + * Called holding the text_mutex. + * + * Modify possibly multiple mutually-dependent pv-op callsites + * (ex. pv_lock_ops) using stop_machine(). + * + * Return: 0 on success, -errno on failure. + */ +int paravirt_runtime_patch(void) +{ + lockdep_assert_held(&text_mutex); + + if (!pv_stage.count) + return -EINVAL; + + return text_poke_late(paravirt_worker, &pv_stage); +} #endif /* CONFIG_PARAVIRT_RUNTIME */