[PATCH v1] armv8: MMU: Fix the memory map for RAM
Patrick DELAUNAY
patrick.delaunay at st.com
Fri Sep 4 13:48:06 CEST 2020
Hi Marek,
> From: U-Boot <u-boot-bounces at lists.denx.de> On Behalf Of Marek Bykowski
> Sent: jeudi 3 septembre 2020 02:01
> To: trini at konsulko.com; sjg at chromium.org; u-boot at lists.denx.de
> Cc: Marek Bykowski <marek.bykowski at gmail.com>
> Subject: [PATCH v1] armv8: MMU: Fix the memory map for RAM
>
> From: Marek Bykowski <marek.bykowski at gmail.com>
>
> The objective of this patch is to impose the correct attributes to the RAM memory
> for the ARM CPU, as shown in the diagram below:
>
> ------------------
> Non-Cached | | Read-Write
> Ordered | Peripherals | Not-Executable
> -----------------|
> | | Read-Write
> Cacheable | Data | Not-Executable
> -----------------|
> | | Read-Only
> Cacheable | Code | Not-Executable
Code is executable I think...
> -----------------|
> |Non-U-Boot image| Read-Write
> Cacheable | eg. efi | Executable
> ------------------
>
> U-Boot adheres into attributing the peripheral region/s into Read-Write, Not-
> Executable but it actually fails attributing the RAM correctly.
> It combines the whole RAM into Read-Write, Executable, in which the Code should
> be Read-Only, Executable and the Data - Read-Write, Non-Executable.
> Also the (optional) Non-U-Boot region/s, eg. EFI, PSCI, holding the Code and Data
> need updating but it is left to the developers of the image/s to do so, if needed.
> Generally any new mapping introduced should take account of the appropriate
> attributes for the Instructions and Data.
>
> The reason it is important is that these attrributes control how the processor
> interacts with a location. Such as, if a location the ARM CPU is accessing is
> Executable (translation table descriptor Execute-Never attribute bit cleared) then
> the ARM CPU fetches a number of instructions from that location, all at the same
> time. For example, Cortex-A57 can source up to 128 bits per fetch depending on
> an alignment. If the CPU mispredicts to the Execute-Never region, it creates the
> memory fault but it actually never uses the instructions mispredicted. The CPU
> branches away elsewhere.
>
> Therefore, as long as the MMU is programmed correctly these mispredictions will
> only affect the performance. But if we fail programming the MMU correctly and if
> the instruction fetch logic mispredicts to the non-instruction memory it may
> eventually perturb it, eg. corrupt the FIFO, the control registers, or load the unified
> cache with the instructions the data side memory system hits into subsequently.
>
> Following an application of the memory map as per-diagram above an attempt to
> execute an instruction fetched from the Non-Executable memory creates an
> Instruction Abort. Similarly, an attempt to Write to an address marked as Read-
> Only will result in with a Data Abort. Both aborts are labelled as Permission Faults
> and are easy to catch by the processor.
If all DDR is " Not-Executable", excepted code of U-boot himself and EFI, I think that
the standalone application can't be more execute except if the MMU configuration
change before to execute it.
See do_bootm_standalone().
PS: it is done for Linux in do_bootm_linux/ do_bootm_linux/ announce_and_cleanup.....
caches ans MMU are deactivated
For information I have the same issue on armV7 platform stm32mp1: speculative access
on memory, used by OP-TEE, protected by firewall.
I propose a other solution [1]: no more map the reserved memory region with the property
"no-map", bt only for cache-cp15.
It is based lmb library so it could done also in armv8 cache functions.
[1] http://patchwork.ozlabs.org/project/uboot/list/?series=199486
> Signed-off-by: Marek Bykowski <marek.bykowski at gmail.com>
> ---
> Changes in PATCH v1:
> - now it re-maps the whole RAM to the proper attributes,
> - took account of other images, eg. PSCI, EFI that need a separate attention
> - it has been tested on qemu arm 64 and two of my armv8 boards, one is Axxia
> series of the processor, the other is so early that the name cannot be
> revealed yet
>
> arch/arm/cpu/armv8/cache_v8.c | 103
> +++++++++++++++++++++++++++++++
> arch/arm/cpu/armv8/u-boot.lds | 39 ++++++++++--
> arch/arm/include/asm/armv8/mmu.h | 6 ++
> arch/arm/lib/sections.c | 19 ++++--
> include/asm-generic/sections.h | 9 +++
> 5 files changed, 164 insertions(+), 12 deletions(-)
>
> diff --git a/arch/arm/cpu/armv8/cache_v8.c b/arch/arm/cpu/armv8/cache_v8.c
> index 7c31d98a6f..4d8843d05e 100644
> --- a/arch/arm/cpu/armv8/cache_v8.c
> +++ b/arch/arm/cpu/armv8/cache_v8.c
> @@ -14,6 +14,7 @@
> #include <asm/cache.h>
> #include <asm/system.h>
> #include <asm/armv8/mmu.h>
> +#include <asm/sections.h>
>
> DECLARE_GLOBAL_DATA_PTR;
>
> @@ -364,6 +365,100 @@ __weak u64 get_page_table_size(void)
> return size;
> }
>
> +__weak void force_remaping_ram(void)
> +{
> + int i = 0;
> +
> + if (!(gd->flags & GD_FLG_RELOC))
> + return;
> +
> + struct mm_region mem_map_ram[] = {
> + /*
> + * Re-map the whole RAM to Read-Write, Non-Executable, and
> + * then .text section/s to Read-Only, Executable.
> + */
> + {
> + .virt = (u64)gd->ram_base,
> + .phys = (u64)gd->ram_base,
> + .size = (u64)gd->ram_size,
> + .attrs = PTE_BLOCK_MEMTYPE(MT_NORMAL) |
> + PTE_BLOCK_INNER_SHARE |
> + PTE_BLOCK_UXN
> + },
> +#if IS_ENABLED(CONFIG_EFI_LOADER)
> + {
> + .virt = (u64)__efi_runtime_start_section,
> + .phys = (u64)__efi_runtime_start_section,
> + .size = (u64)(__efi_runtime_stop_section -
> + __efi_runtime_start_section),
> + .attrs = (PTE_BLOCK_MEMTYPE(MT_NORMAL) |
> + PTE_BLOCK_INNER_SHARE) &
> ~PTE_BLOCK_UXN
> + },
> + {
> + .virt = (u64)__efi_runtime_rel_start_section,
> + .phys = (u64)__efi_runtime_rel_start_section,
> + .size = (u64)(__efi_runtime_rel_stop_section -
> + __efi_runtime_rel_start_section),
> + .attrs = (PTE_BLOCK_MEMTYPE(MT_NORMAL) |
> + PTE_BLOCK_INNER_SHARE) &
> ~PTE_BLOCK_UXN
> + },
> +#endif
> + {
> + .virt = (u64)__image_copy_start,
> + .phys = (u64)__image_copy_start,
> + .size = (u64)(__text_end - __image_copy_start),
> + .attrs = (PTE_BLOCK_MEMTYPE(MT_NORMAL) |
> + PTE_BLOCK_INNER_SHARE |
> PTE_BLOCK_AP_RO) &
> + ~PTE_BLOCK_UXN
> + },
> + {
> + .virt = (u64)__text_rest_start,
> + .phys = (u64)__text_rest_start,
> + .size = (u64)(__text_rest_end - __text_rest_start),
> + .attrs = (PTE_BLOCK_MEMTYPE(MT_NORMAL) |
> + PTE_BLOCK_INNER_SHARE |
> PTE_BLOCK_AP_RO) &
> + ~PTE_BLOCK_UXN
> + },
> +#if IS_ENABLED(CONFIG_ARMV8_SECURE_BASE)
> + {
> + .virt = (u64)__secure_text_start,
> + .phys = (u64)__secure_text_start,
> + .size = (u64)(__secure_text_end - __secure_text_start),
> + .attrs = (PTE_BLOCK_MEMTYPE(MT_NORMAL) |
> + PTE_BLOCK_INNER_SHARE |
> PTE_BLOCK_AP_RO) &
> + ~PTE_BLOCK_UXN
> + },
> +#endif
> + { 0 }
> + };
> +
> + debug("Re-mapping RAM: Code to RO,XN=0, Data - RW,XN=1");
> + if (IS_ENABLED(CONFIG_EFI_LOADER) ||
> IS_ENABLED(CONFIG_ARMV8_SECURE_BASE))
> + debug(", Non-U-Boot images (eg. efi, psci) - RW,XN=0
> (unchanged)");
> + debug("\n");
> +
> + for (; mem_map_ram[i].size || mem_map_ram[i].attrs; i++) {
> + /*
> + * MT_NORMAL - Normal Memory
> + * MT_DEVICE_NGNRNE - Device Memory (we don't expect that
> + * really for the RAM to happen...)
> + * RO - read-only
> + * RW - read-write
> + * XN=0 - Executable
> + * XN=1 - Non-executable
> + */
> + debug("[%d]: 0x%llx-0x%llx %s%s%s\n",
> + i, mem_map_ram[i].phys, mem_map_ram[i].phys +
> + mem_map_ram[i].size,
> + mem_map_ram[i].attrs &
> PTE_BLOCK_MEMTYPE(MT_NORMAL) ?
> + "MT_NORMAL" : "MT_DEVICE",
> + mem_map_ram[i].attrs & PTE_BLOCK_AP_RO ? "-RO" : "-
> RW",
> + mem_map_ram[i].attrs & PTE_BLOCK_UXN ?
> + "-XN=1" : "-XN=0");
> + add_map(&mem_map_ram[i]);
> + }
> +}
> +
> void setup_pgtables(void)
> {
> int i;
> @@ -381,6 +476,14 @@ void setup_pgtables(void)
> /* Now add all MMU table entries one after another to the table */
> for (i = 0; mem_map[i].size || mem_map[i].attrs; i++)
> add_map(&mem_map[i]);
> +
> + /*
> + * Force re-mapping RAM only if the generic linker script in use.
> + * The boundaries of the regions for re-mapping are defined in
> + * the generic ARM64 ld script and won't work for the custom ones.
> + */
> + if (!IS_ENABLED(CONFIG_SYS_CUSTOM_LDSCRIPT))
> + force_remaping_ram();
> }
>
> static void setup_all_pgtables(void)
> diff --git a/arch/arm/cpu/armv8/u-boot.lds b/arch/arm/cpu/armv8/u-boot.lds index
> 2554980595..8e98b143d5 100644
> --- a/arch/arm/cpu/armv8/u-boot.lds
> +++ b/arch/arm/cpu/armv8/u-boot.lds
> @@ -9,6 +9,7 @@
>
> #include <config.h>
> #include <asm/psci.h>
> +#include <asm/armv8/mmu.h>
>
> OUTPUT_FORMAT("elf64-littleaarch64", "elf64-littleaarch64", "elf64-
> littleaarch64")
> OUTPUT_ARCH(aarch64)
> @@ -20,25 +21,36 @@ SECTIONS
> #endif
> . = 0x00000000;
>
> - . = ALIGN(8);
> + /* Align .text to the page size */
> + . = ALIGN(PAGE_SIZE);
> .text :
> {
> *(.__image_copy_start)
> CPUDIR/start.o (.text*)
> + . = ALIGN(PAGE_SIZE);
> + KEEP(*(.__text_end))
> }
>
> /* This needs to come before *(.text*) */
> - .efi_runtime : {
> - __efi_runtime_start = .;
> + .efi_runtime ALIGN(CONSTANT(COMMONPAGESIZE)):
> + {
> + KEEP(*(.__efi_runtime_start))
> + __efi_runtime_start = .;
> *(.text.efi_runtime*)
> *(.rodata.efi_runtime*)
> *(.data.efi_runtime*)
> - __efi_runtime_stop = .;
> + __efi_runtime_stop = .;
> + . = ALIGN(PAGE_SIZE);
> + KEEP(*(.__efi_runtime_stop))
> }
>
> + . = ALIGN(PAGE_SIZE);
> .text_rest :
> {
> + KEEP(*(.__text_rest_start))
> *(.text*)
> + . = ALIGN(PAGE_SIZE);
> + KEEP(*(.__text_rest_end))
> }
>
> #ifdef CONFIG_ARMV8_PSCI
> @@ -54,14 +66,18 @@ SECTIONS
> #define CONFIG_ARMV8_SECURE_BASE
> #define __ARMV8_PSCI_STACK_IN_RAM
> #endif
> + . = ALIGN(PAGE_SIZE);
> .secure_text CONFIG_ARMV8_SECURE_BASE :
> AT(ADDR(.__secure_start) + SIZEOF(.__secure_start))
> {
> + KEEP(*(.__secure_text_start))
> *(._secure.text)
> . = ALIGN(8);
> __secure_svc_tbl_start = .;
> KEEP(*(._secure_svc_tbl_entries))
> __secure_svc_tbl_end = .;
> + . = ALIGN(PAGE_SIZE);
> + KEEP(*(.__secure_text_end))
> }
>
> .secure_data : AT(LOADADDR(.secure_text) + SIZEOF(.secure_text))
> @@ -113,15 +129,26 @@ SECTIONS
> KEEP(*(SORT(.u_boot_list*)));
> }
>
> - . = ALIGN(8);
> + . = ALIGN(PAGE_SIZE);
> + .efi_runtime_rel_start :
> + {
> + KEEP(*(.__efi_runtime_rel_start))
> + }
>
> - .efi_runtime_rel : {
> + .efi_runtime_rel :
> + {
> __efi_runtime_rel_start = .;
> *(.rel*.efi_runtime)
> *(.rel*.efi_runtime.*)
> __efi_runtime_rel_stop = .;
> }
>
> + . = ALIGN(PAGE_SIZE);
> + .efi_runtime_rel_stop :
> + {
> + KEEP(*(.__efi_runtime_rel_stop))
> + }
> +
> . = ALIGN(8);
>
> .image_copy_end :
> diff --git a/arch/arm/include/asm/armv8/mmu.h
> b/arch/arm/include/asm/armv8/mmu.h
> index fc97c55114..571cc283eb 100644
> --- a/arch/arm/include/asm/armv8/mmu.h
> +++ b/arch/arm/include/asm/armv8/mmu.h
> @@ -59,6 +59,12 @@
> */
> #define PTE_BLOCK_MEMTYPE(x) ((x) << 2)
> #define PTE_BLOCK_NS (1 << 5)
> +/*
> + * AP[1] bit is ignored by hardware and is
> + * treated as if it was One in EL2/EL3
> + */
> +#define PTE_BLOCK_AP_RO (1 << 7)
> +#define PTE_BLOCK_AP_RW (0 << 7)
> #define PTE_BLOCK_NON_SHARE (0 << 8)
> #define PTE_BLOCK_OUTER_SHARE (2 << 8)
> #define PTE_BLOCK_INNER_SHARE (3 << 8)
> diff --git a/arch/arm/lib/sections.c b/arch/arm/lib/sections.c index
> 3bb2d8468c..b00d24843d 100644
> --- a/arch/arm/lib/sections.c
> +++ b/arch/arm/lib/sections.c
> @@ -3,6 +3,8 @@
> * Copyright 2013 Albert ARIBAUD <albert.u.boot at aribaud.net>
> */
>
> +#include <linux/compiler_types.h>
> +
> /**
> * These two symbols are declared in a C file so that the linker
> * uses R_ARM_RELATIVE relocation, rather than the R_ARM_ABS32 one @@ -
> 18,6 +20,11 @@
> * aliasing warnings.
> */
>
> +char __text_end[0] __section(".__text_end"); char __text_rest_start[0]
> +__section(".__text_rest_start"); char __text_rest_end[0]
> +__section(".__text_rest_end"); char __secure_text_start[0]
> +__section(".__secure_text_start");
> +char __secure_text_end[0] __section(".__secure_text_end");
> char __bss_start[0] __attribute__((section(".__bss_start")));
> char __bss_end[0] __attribute__((section(".__bss_end")));
> char __image_copy_start[0] __attribute__((section(".__image_copy_start")));
> @@ -26,10 +33,10 @@ char __rel_dyn_start[0]
> __attribute__((section(".__rel_dyn_start")));
> char __rel_dyn_end[0] __attribute__((section(".__rel_dyn_end")));
> char __secure_start[0] __attribute__((section(".__secure_start")));
> char __secure_end[0] __attribute__((section(".__secure_end")));
> -char __secure_stack_start[0] __attribute__((section(".__secure_stack_start")));
> -char __secure_stack_end[0] __attribute__((section(".__secure_stack_end")));
> -char __efi_runtime_start[0] __attribute__((section(".__efi_runtime_start")));
> -char __efi_runtime_stop[0] __attribute__((section(".__efi_runtime_stop")));
> -char __efi_runtime_rel_start[0]
> __attribute__((section(".__efi_runtime_rel_start")));
> -char __efi_runtime_rel_stop[0] __attribute__((section(".__efi_runtime_rel_stop")));
> +char __secure_stack_start[0] __section(".__secure_stack_start");
> +char __secure_stack_end[0] __section(".__secure_stack_end"); char
> +__efi_runtime_start_section[0] __section(".__efi_runtime_start");
> +char __efi_runtime_stop_section[0] __section(".__efi_runtime_stop");
> +char __efi_runtime_rel_start_section[0]
> +__section(".__efi_runtime_rel_start");
> +char __efi_runtime_rel_stop_section[0]
> +__section(".__efi_runtime_rel_stop");
> char _end[0] __attribute__((section(".__end")));
> diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index
> 0577238d60..c3dc0522ee 100644
> --- a/include/asm-generic/sections.h
> +++ b/include/asm-generic/sections.h
> @@ -72,6 +72,11 @@ extern void _start(void);
> */
> #ifdef CONFIG_ARM
>
> +extern char __text_end[];
> +extern char __text_rest_start[];
> +extern char __text_rest_end[];
> +extern char __secure_text_start[];
> +extern char __secure_text_end[];
> extern char __bss_start[];
> extern char __bss_end[];
> extern char __image_copy_start[];
> @@ -79,6 +84,10 @@ extern char __image_copy_end[]; extern char
> _image_binary_end[]; extern char __rel_dyn_start[]; extern char __rel_dyn_end[];
> +extern char __efi_runtime_start_section[]; extern char
> +__efi_runtime_stop_section[]; extern char
> +__efi_runtime_rel_start_section[];
> +extern char __efi_runtime_rel_stop_section[];
>
> #else /* don't use offsets: */
>
> --
> 2.21.0.896.g6a6c0f1
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