kernel.git/arch/arm/kernel/entry-armv.S, branch linux-5.13.y

ARM: 9030/1: entry: omit FP emulation for UND exceptions taken in kernel mode

2020-12-08T10:15:00Z

There are a couple of problems with the exception entry code that deals with FP exceptions (which are reported as UND exceptions) when building the kernel in Thumb2 mode: - the conditional branch to vfp_kmode_exception in vfp_support_entry() may be out of range for its target, depending on how the linker decides to arrange the sections; - when the UND exception is taken in kernel mode, the emulation handling logic is entered via the 'call_fpe' label, which means we end up using the wrong value/mask pairs to match and detect the NEON opcodes. Since UND exceptions in kernel mode are unlikely to occur on a hot path (as opposed to the user mode version which is invoked for VFP support code and lazy restore), we can use the existing undef hook machinery for any kernel mode instruction emulation that is needed, including calling the existing vfp_kmode_exception() routine for unexpected cases. So drop the call to call_fpe, and instead, install an undef hook that will get called for NEON and VFP instructions that trigger an UND exception in kernel mode. While at it, make sure that the PC correction is accurate for the execution mode where the exception was taken, by checking the PSR Thumb bit. Cc: Dmitry Osipenko Cc: Kees Cook Fixes: eff8728fe698 ("vmlinux.lds.h: Add PGO and AutoFDO input sections") Signed-off-by: Ard Biesheuvel Reviewed-by: Linus Walleij Reviewed-by: Nick Desaulniers Signed-off-by: Russell King

ARM: 9015/2: Define the virtual space of KASan's shadow region

2020-10-27T12:11:08Z

Define KASAN_SHADOW_OFFSET,KASAN_SHADOW_START and KASAN_SHADOW_END for the Arm kernel address sanitizer. We are "stealing" lowmem (the 4GB addressable by a 32bit architecture) out of the virtual address space to use as shadow memory for KASan as follows: +----+ 0xffffffff | | | | |-> Static kernel image (vmlinux) BSS and page table | |/ +----+ PAGE_OFFSET | | | | |-> Loadable kernel modules virtual address space area | |/ +----+ MODULES_VADDR = KASAN_SHADOW_END | | | | |-> The shadow area of kernel virtual address. | |/ +----+-> TASK_SIZE (start of kernel space) = KASAN_SHADOW_START the | | shadow address of MODULES_VADDR | | | | | | | | |-> The user space area in lowmem. The kernel address | | | sanitizer do not use this space, nor does it map it. | | | | | | | | | | | | | |/ ------ 0 0 .. TASK_SIZE is the memory that can be used by shared userspace/kernelspace. It us used for userspace processes and for passing parameters and memory buffers in system calls etc. We do not need to shadow this area. KASAN_SHADOW_START: This value begins with the MODULE_VADDR's shadow address. It is the start of kernel virtual space. Since we have modules to load, we need to cover also that area with shadow memory so we can find memory bugs in modules. KASAN_SHADOW_END This value is the 0x100000000's shadow address: the mapping that would be after the end of the kernel memory at 0xffffffff. It is the end of kernel address sanitizer shadow area. It is also the start of the module area. KASAN_SHADOW_OFFSET: This value is used to map an address to the corresponding shadow address by the following formula: shadow_addr = (address >> 3) + KASAN_SHADOW_OFFSET; As you would expect, >> 3 is equal to dividing by 8, meaning each byte in the shadow memory covers 8 bytes of kernel memory, so one bit shadow memory per byte of kernel memory is used. The KASAN_SHADOW_OFFSET is provided in a Kconfig option depending on the VMSPLIT layout of the system: the kernel and userspace can split up lowmem in different ways according to needs, so we calculate the shadow offset depending on this. When kasan is enabled, the definition of TASK_SIZE is not an 8-bit rotated constant, so we need to modify the TASK_SIZE access code in the *.s file. The kernel and modules may use different amounts of memory, according to the VMSPLIT configuration, which in turn determines the PAGE_OFFSET. We use the following KASAN_SHADOW_OFFSETs depending on how the virtual memory is split up: - 0x1f000000 if we have 1G userspace / 3G kernelspace split: - The kernel address space is 3G (0xc0000000) - PAGE_OFFSET is then set to 0x40000000 so the kernel static image (vmlinux) uses addresses 0x40000000 .. 0xffffffff - On top of that we have the MODULES_VADDR which under the worst case (using ARM instructions) is PAGE_OFFSET - 16M (0x01000000) = 0x3f000000 so the modules use addresses 0x3f000000 .. 0x3fffffff - So the addresses 0x3f000000 .. 0xffffffff need to be covered with shadow memory. That is 0xc1000000 bytes of memory. - 1/8 of that is needed for its shadow memory, so 0x18200000 bytes of shadow memory is needed. We "steal" that from the remaining lowmem. - The KASAN_SHADOW_START becomes 0x26e00000, to KASAN_SHADOW_END at 0x3effffff. - Now we can calculate the KASAN_SHADOW_OFFSET for any kernel address as 0x3f000000 needs to map to the first byte of shadow memory and 0xffffffff needs to map to the last byte of shadow memory. Since: SHADOW_ADDR = (address >> 3) + KASAN_SHADOW_OFFSET 0x26e00000 = (0x3f000000 >> 3) + KASAN_SHADOW_OFFSET KASAN_SHADOW_OFFSET = 0x26e00000 - (0x3f000000 >> 3) KASAN_SHADOW_OFFSET = 0x26e00000 - 0x07e00000 KASAN_SHADOW_OFFSET = 0x1f000000 - 0x5f000000 if we have 2G userspace / 2G kernelspace split: - The kernel space is 2G (0x80000000) - PAGE_OFFSET is set to 0x80000000 so the kernel static image uses 0x80000000 .. 0xffffffff. - On top of that we have the MODULES_VADDR which under the worst case (using ARM instructions) is PAGE_OFFSET - 16M (0x01000000) = 0x7f000000 so the modules use addresses 0x7f000000 .. 0x7fffffff - So the addresses 0x7f000000 .. 0xffffffff need to be covered with shadow memory. That is 0x81000000 bytes of memory. - 1/8 of that is needed for its shadow memory, so 0x10200000 bytes of shadow memory is needed. We "steal" that from the remaining lowmem. - The KASAN_SHADOW_START becomes 0x6ee00000, to KASAN_SHADOW_END at 0x7effffff. - Now we can calculate the KASAN_SHADOW_OFFSET for any kernel address as 0x7f000000 needs to map to the first byte of shadow memory and 0xffffffff needs to map to the last byte of shadow memory. Since: SHADOW_ADDR = (address >> 3) + KASAN_SHADOW_OFFSET 0x6ee00000 = (0x7f000000 >> 3) + KASAN_SHADOW_OFFSET KASAN_SHADOW_OFFSET = 0x6ee00000 - (0x7f000000 >> 3) KASAN_SHADOW_OFFSET = 0x6ee00000 - 0x0fe00000 KASAN_SHADOW_OFFSET = 0x5f000000 - 0x9f000000 if we have 3G userspace / 1G kernelspace split, and this is the default split for ARM: - The kernel address space is 1GB (0x40000000) - PAGE_OFFSET is set to 0xc0000000 so the kernel static image uses 0xc0000000 .. 0xffffffff. - On top of that we have the MODULES_VADDR which under the worst case (using ARM instructions) is PAGE_OFFSET - 16M (0x01000000) = 0xbf000000 so the modules use addresses 0xbf000000 .. 0xbfffffff - So the addresses 0xbf000000 .. 0xffffffff need to be covered with shadow memory. That is 0x41000000 bytes of memory. - 1/8 of that is needed for its shadow memory, so 0x08200000 bytes of shadow memory is needed. We "steal" that from the remaining lowmem. - The KASAN_SHADOW_START becomes 0xb6e00000, to KASAN_SHADOW_END at 0xbfffffff. - Now we can calculate the KASAN_SHADOW_OFFSET for any kernel address as 0xbf000000 needs to map to the first byte of shadow memory and 0xffffffff needs to map to the last byte of shadow memory. Since: SHADOW_ADDR = (address >> 3) + KASAN_SHADOW_OFFSET 0xb6e00000 = (0xbf000000 >> 3) + KASAN_SHADOW_OFFSET KASAN_SHADOW_OFFSET = 0xb6e00000 - (0xbf000000 >> 3) KASAN_SHADOW_OFFSET = 0xb6e00000 - 0x17e00000 KASAN_SHADOW_OFFSET = 0x9f000000 - 0x8f000000 if we have 3G userspace / 1G kernelspace with full 1 GB low memory (VMSPLIT_3G_OPT): - The kernel address space is 1GB (0x40000000) - PAGE_OFFSET is set to 0xb0000000 so the kernel static image uses 0xb0000000 .. 0xffffffff. - On top of that we have the MODULES_VADDR which under the worst case (using ARM instructions) is PAGE_OFFSET - 16M (0x01000000) = 0xaf000000 so the modules use addresses 0xaf000000 .. 0xaffffff - So the addresses 0xaf000000 .. 0xffffffff need to be covered with shadow memory. That is 0x51000000 bytes of memory. - 1/8 of that is needed for its shadow memory, so 0x0a200000 bytes of shadow memory is needed. We "steal" that from the remaining lowmem. - The KASAN_SHADOW_START becomes 0xa4e00000, to KASAN_SHADOW_END at 0xaeffffff. - Now we can calculate the KASAN_SHADOW_OFFSET for any kernel address as 0xaf000000 needs to map to the first byte of shadow memory and 0xffffffff needs to map to the last byte of shadow memory. Since: SHADOW_ADDR = (address >> 3) + KASAN_SHADOW_OFFSET 0xa4e00000 = (0xaf000000 >> 3) + KASAN_SHADOW_OFFSET KASAN_SHADOW_OFFSET = 0xa4e00000 - (0xaf000000 >> 3) KASAN_SHADOW_OFFSET = 0xa4e00000 - 0x15e00000 KASAN_SHADOW_OFFSET = 0x8f000000 - The default value of 0xffffffff for KASAN_SHADOW_OFFSET is an error value. We should always match one of the above shadow offsets. When we do this, TASK_SIZE will sometimes get a bit odd values that will not fit into immediate mov assembly instructions. To account for this, we need to rewrite some assembly using TASK_SIZE like this: - mov r1, #TASK_SIZE + ldr r1, =TASK_SIZE or - cmp r4, #TASK_SIZE + ldr r0, =TASK_SIZE + cmp r4, r0 this is done to avoid the immediate #TASK_SIZE that need to fit into a limited number of bits. Cc: Andrey Ryabinin Cc: Alexander Potapenko Cc: Dmitry Vyukov Cc: kasan-dev@googlegroups.com Cc: Mike Rapoport Reviewed-by: Ard Biesheuvel Tested-by: Ard Biesheuvel # QEMU/KVM/mach-virt/LPAE/8G Tested-by: Florian Fainelli # Brahma SoCs Tested-by: Ahmad Fatoum # i.MX6Q Reported-by: Ard Biesheuvel Signed-off-by: Abbott Liu Signed-off-by: Florian Fainelli Signed-off-by: Linus Walleij Signed-off-by: Russell King

ARM: uaccess: consolidate uaccess asm to asm/uaccess-asm.h

2020-05-03T16:30:24Z

Consolidate the user access assembly code to asm/uaccess-asm.h. This moves the csdb, check_uaccess, uaccess_mask_range_ptr, uaccess_enable, uaccess_disable, uaccess_save, uaccess_restore macros, and creates two new ones for exception entry and exit - uaccess_entry and uaccess_exit. This makes the uaccess_save and uaccess_restore macros private to asm/uaccess-asm.h. Signed-off-by: Russell King

sched/rt, ARM: Use CONFIG_PREEMPTION

2019-12-08T13:37:32Z

CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT. Both PREEMPT and PREEMPT_RT require the same functionality which today depends on CONFIG_PREEMPT. Switch the entry code, cache over to use CONFIG_PREEMPTION and add output in show_stack() for PREEMPT_RT. [bigeasy: +traps.c] Signed-off-by: Thomas Gleixner Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Russell King Cc: linux-arm-kernel@lists.infradead.org Link: https://lore.kernel.org/r/20191015191821.11479-2-bigeasy@linutronix.de Signed-off-by: Ingo Molnar

docs: arm: convert docs to ReST and rename to *.rst

2019-07-15T12:20:24Z

Converts ARM the text files to ReST, preparing them to be an architecture book. The conversion is actually: - add blank lines and identation in order to identify paragraphs; - fix tables markups; - add some lists markups; - mark literal blocks; - adjust title markups. At its new index.rst, let's add a :orphan: while this is not linked to the main index.rst file, in order to avoid build warnings. Signed-off-by: Mauro Carvalho Chehab Reviewed-by Corentin Labbe # For sun4i-ss

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

2019-06-19T15:09:55Z

Based on 2 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation # extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 4122 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Enrico Weigelt Reviewed-by: Kate Stewart Reviewed-by: Allison Randal Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de Signed-off-by: Greg Kroah-Hartman

ARM: 8844/1: use unified assembler in assembly files

2019-02-26T11:26:07Z

Use unified assembler syntax (UAL) in assembly files. Divided syntax is considered deprecated. This will also allow to build the kernel using LLVM's integrated assembler. Signed-off-by: Stefan Agner Acked-by: Nicolas Pitre Signed-off-by: Russell King

ARM: Convert to GENERIC_IRQ_MULTI_HANDLER

2018-08-03T10:14:08Z

Converts the ARM interrupt code to use the recently added GENERIC_IRQ_MULTI_HANDLER, which is essentially just a copy of ARM's existhing MULTI_IRQ_HANDLER. The only changes are: * handle_arch_irq is now defined in a generic C file instead of an arm-specific assembly file. * handle_arch_irq is now marked as __ro_after_init. Signed-off-by: Palmer Dabbelt Signed-off-by: Thomas Gleixner Cc: linux@armlinux.org.uk Cc: catalin.marinas@arm.com Cc: Will Deacon Cc: jonas@southpole.se Cc: stefan.kristiansson@saunalahti.fi Cc: shorne@gmail.com Cc: jason@lakedaemon.net Cc: marc.zyngier@arm.com Cc: Arnd Bergmann Cc: nicolas.pitre@linaro.org Cc: vladimir.murzin@arm.com Cc: keescook@chromium.org Cc: jinb.park7@gmail.com Cc: yamada.masahiro@socionext.com Cc: alexandre.belloni@bootlin.com Cc: pombredanne@nexb.com Cc: Greg KH Cc: kstewart@linuxfoundation.org Cc: jhogan@kernel.org Cc: mark.rutland@arm.com Cc: ard.biesheuvel@linaro.org Cc: james.morse@arm.com Cc: linux-arm-kernel@lists.infradead.org Cc: openrisc@lists.librecores.org Link: https://lkml.kernel.org/r/20180622170126.6308-3-palmer@sifive.com

Kbuild: rename CC_STACKPROTECTOR[_STRONG] config variables

2018-06-14T03:21:18Z

The changes to automatically test for working stack protector compiler support in the Kconfig files removed the special STACKPROTECTOR_AUTO option that picked the strongest stack protector that the compiler supported. That was all a nice cleanup - it makes no sense to have the AUTO case now that the Kconfig phase can just determine the compiler support directly. HOWEVER. It also meant that doing "make oldconfig" would now _disable_ the strong stackprotector if you had AUTO enabled, because in a legacy config file, the sane stack protector configuration would look like CONFIG_HAVE_CC_STACKPROTECTOR=y # CONFIG_CC_STACKPROTECTOR_NONE is not set # CONFIG_CC_STACKPROTECTOR_REGULAR is not set # CONFIG_CC_STACKPROTECTOR_STRONG is not set CONFIG_CC_STACKPROTECTOR_AUTO=y and when you ran this through "make oldconfig" with the Kbuild changes, it would ask you about the regular CONFIG_CC_STACKPROTECTOR (that had been renamed from CONFIG_CC_STACKPROTECTOR_REGULAR to just CONFIG_CC_STACKPROTECTOR), but it would think that the STRONG version used to be disabled (because it was really enabled by AUTO), and would disable it in the new config, resulting in: CONFIG_HAVE_CC_STACKPROTECTOR=y CONFIG_CC_HAS_STACKPROTECTOR_NONE=y CONFIG_CC_STACKPROTECTOR=y # CONFIG_CC_STACKPROTECTOR_STRONG is not set CONFIG_CC_HAS_SANE_STACKPROTECTOR=y That's dangerously subtle - people could suddenly find themselves with the weaker stack protector setup without even realizing. The solution here is to just rename not just the old RECULAR stack protector option, but also the strong one. This does that by just removing the CC_ prefix entirely for the user choices, because it really is not about the compiler support (the compiler support now instead automatially impacts _visibility_ of the options to users). This results in "make oldconfig" actually asking the user for their choice, so that we don't have any silent subtle security model changes. The end result would generally look like this: CONFIG_HAVE_CC_STACKPROTECTOR=y CONFIG_CC_HAS_STACKPROTECTOR_NONE=y CONFIG_STACKPROTECTOR=y CONFIG_STACKPROTECTOR_STRONG=y CONFIG_CC_HAS_SANE_STACKPROTECTOR=y where the "CC_" versions really are about internal compiler infrastructure, not the user selections. Acked-by: Masahiro Yamada Signed-off-by: Linus Torvalds

ARM: probes: avoid adding kprobes to sensitive kernel-entry/exit code

2017-12-17T22:14:21Z

Avoid adding kprobes to any of the kernel entry/exit or startup assembly code, or code in the identity-mapped region. This code does not conform to the standard C conventions, which means that the expectations of the kprobes code is not forfilled. Placing kprobes at some of these locations results in the kernel trying to return to userspace addresses while retaining the CPU in kernel mode. Tested-by: Naresh Kamboju Signed-off-by: Russell King