Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751462AbdH1XnH (ORCPT ); Mon, 28 Aug 2017 19:43:07 -0400 Received: from mga03.intel.com ([134.134.136.65]:52826 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751275AbdH1Xmj (ORCPT ); Mon, 28 Aug 2017 19:42:39 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,442,1498546800"; d="scan'208";a="123458655" From: Sai Praneeth Prakhya To: linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, matt@codeblueprint.co.uk, ard.biesheuvel@linaro.org Cc: jlee@suse.com, bp@alien8.de, tony.luck@intel.com, luto@kernel.org, mst@redhat.com, ricardo.neri@intel.com, ravi.v.shankar@intel.com, Sai Praneeth Subject: [PATCH V2 3/3] x86/efi: Use efi_switch_mm() rather than manually twiddling with %cr3 Date: Mon, 28 Aug 2017 16:37:12 -0700 Message-Id: <1503963432-32055-4-git-send-email-sai.praneeth.prakhya@intel.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1503963432-32055-1-git-send-email-sai.praneeth.prakhya@intel.com> References: <1503963432-32055-1-git-send-email-sai.praneeth.prakhya@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6568 Lines: 205 From: Sai Praneeth Use helper function (efi_switch_mm()) to switch to/from efi_mm. We switch to efi_mm before calling 1. efi_set_virtual_address_map() and 2. Invoking any efi_runtime_service() Likewise, we need to switch back to previous mm (mm context stolen by efi_mm) after the above calls return successfully. We can use efi_switch_mm() helper function only with x86_64 kernel and "efi=old_map" disabled because, x86_32 and efi=old_map doesn't use efi_pgd, rather they use swapper_pg_dir. Signed-off-by: Sai Praneeth Prakhya Cc: Lee, Chun-Yi Cc: Borislav Petkov Cc: Tony Luck Cc: Andy Lutomirski Cc: Michael S. Tsirkin Cc: Ricardo Neri Cc: Matt Fleming Cc: Ard Biesheuvel Cc: Ravi Shankar --- arch/x86/include/asm/efi.h | 29 ++++++++++++++--------------- arch/x86/platform/efi/efi_64.c | 36 +++++++++++++++++++++--------------- arch/x86/platform/efi/efi_thunk_64.S | 2 +- 3 files changed, 36 insertions(+), 31 deletions(-) diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h index 2f77bcefe6b4..23b2137a95e5 100644 --- a/arch/x86/include/asm/efi.h +++ b/arch/x86/include/asm/efi.h @@ -1,10 +1,14 @@ #ifndef _ASM_X86_EFI_H #define _ASM_X86_EFI_H +#include +#include + #include #include #include #include +#include /* * We map the EFI regions needed for runtime services non-contiguously, @@ -57,14 +61,13 @@ extern u64 asmlinkage efi_call(void *fp, ...); #define efi_call_phys(f, args...) efi_call((f), args) /* - * Scratch space used for switching the pagetable in the EFI stub + * struct efi_scratch - Scratch space used while switching to/from efi_mm + * @phys_stack: stack used during EFI Mixed Mode + * @prev_mm: store/restore stolen mm_struct while switching to/from efi_mm */ struct efi_scratch { - u64 r15; - u64 prev_cr3; - pgd_t *efi_pgt; - bool use_pgd; - u64 phys_stack; + u64 phys_stack; + struct mm_struct *prev_mm; } __packed; #define arch_efi_call_virt_setup() \ @@ -73,11 +76,8 @@ struct efi_scratch { preempt_disable(); \ __kernel_fpu_begin(); \ \ - if (efi_scratch.use_pgd) { \ - efi_scratch.prev_cr3 = read_cr3(); \ - write_cr3((unsigned long)efi_scratch.efi_pgt); \ - __flush_tlb_all(); \ - } \ + if (!efi_enabled(EFI_OLD_MEMMAP)) \ + efi_switch_mm(&efi_mm); \ }) #define arch_efi_call_virt(p, f, args...) \ @@ -85,10 +85,8 @@ struct efi_scratch { #define arch_efi_call_virt_teardown() \ ({ \ - if (efi_scratch.use_pgd) { \ - write_cr3(efi_scratch.prev_cr3); \ - __flush_tlb_all(); \ - } \ + if (!efi_enabled(EFI_OLD_MEMMAP)) \ + efi_switch_mm(efi_scratch.prev_mm); \ \ __kernel_fpu_end(); \ preempt_enable(); \ @@ -130,6 +128,7 @@ extern void __init efi_dump_pagetable(void); extern void __init efi_apply_memmap_quirks(void); extern int __init efi_reuse_config(u64 tables, int nr_tables); extern void efi_delete_dummy_variable(void); +extern void efi_switch_mm(struct mm_struct *mm); struct efi_setup_data { u64 fw_vendor; diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index 0bb98c35e178..e0545f56d703 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -80,9 +80,8 @@ pgd_t * __init efi_call_phys_prolog(void) int n_pgds, i, j; if (!efi_enabled(EFI_OLD_MEMMAP)) { - save_pgd = (pgd_t *)read_cr3(); - write_cr3((unsigned long)efi_scratch.efi_pgt); - goto out; + efi_switch_mm(&efi_mm); + return NULL; } early_code_mapping_set_exec(1); @@ -152,8 +151,7 @@ void __init efi_call_phys_epilog(pgd_t *save_pgd) pud_t *pud; if (!efi_enabled(EFI_OLD_MEMMAP)) { - write_cr3((unsigned long)save_pgd); - __flush_tlb_all(); + efi_switch_mm(efi_scratch.prev_mm); return; } @@ -336,8 +334,6 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages) if (efi_enabled(EFI_OLD_MEMMAP)) return 0; - efi_scratch.efi_pgt = (pgd_t *)__pa(pgd); - /* * It can happen that the physical address of new_memmap lands in memory * which is not mapped in the EFI page table. Therefore we need to go @@ -350,8 +346,6 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages) return 1; } - efi_scratch.use_pgd = true; - /* * Certain firmware versions are way too sentimential and still believe * they are exclusive and unquestionable owners of the first physical page, @@ -596,6 +590,22 @@ void __init efi_dump_pagetable(void) #endif } +/* + * Makes the calling thread switch to/from efi_mm context. Can be used + * for SetVirtualAddressMap() i.e. current->active_mm == init_mm as well + * as during efi runtime calls i.e current->active_mm == current_mm. + * We are not mm_dropping()/mm_grabbing() any mm, because we are not + * losing/creating any references. + */ +void efi_switch_mm(struct mm_struct *mm) +{ + task_lock(current); + efi_scratch.prev_mm = current->active_mm; + current->active_mm = mm; + switch_mm(efi_scratch.prev_mm, mm, NULL); + task_unlock(current); +} + #ifdef CONFIG_EFI_MIXED extern efi_status_t efi64_thunk(u32, ...); @@ -649,17 +659,13 @@ efi_status_t efi_thunk_set_virtual_address_map( efi_sync_low_kernel_mappings(); local_irq_save(flags); - efi_scratch.prev_cr3 = read_cr3(); - write_cr3((unsigned long)efi_scratch.efi_pgt); - __flush_tlb_all(); + efi_switch_mm(&efi_mm); func = (u32)(unsigned long)phys_set_virtual_address_map; status = efi64_thunk(func, memory_map_size, descriptor_size, descriptor_version, virtual_map); - write_cr3(efi_scratch.prev_cr3); - __flush_tlb_all(); - local_irq_restore(flags); + efi_switch_mm(efi_scratch.prev_mm); return status; } diff --git a/arch/x86/platform/efi/efi_thunk_64.S b/arch/x86/platform/efi/efi_thunk_64.S index ff85d28c50f2..5cdc72ebbc82 100644 --- a/arch/x86/platform/efi/efi_thunk_64.S +++ b/arch/x86/platform/efi/efi_thunk_64.S @@ -32,7 +32,7 @@ ENTRY(efi64_thunk) * Switch to 1:1 mapped 32-bit stack pointer. */ movq %rsp, efi_saved_sp(%rip) - movq efi_scratch+25(%rip), %rsp + movq efi_scratch(%rip), %rsp /* * Calculate the physical address of the kernel text. -- 2.1.4