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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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![Bryan O'Donoghue](/assets/img/avatar_default.png)
Intel's Quark X1000 SoC contains a set of registers called Isolated Memory Regions. IMRs are accessed over the IOSF mailbox interface. IMRs are areas carved out of memory that define read/write access rights to the various system agents within the Quark system. For a given agent in the system it is possible to specify if that agent may read or write an area of memory defined by an IMR with a granularity of 1 KiB. Quark_SecureBootPRM_330234_001.pdf section 4.5 details the concept of IMRs quark-x1000-datasheet.pdf section 12.7.4 details the implementation of IMRs in silicon. eSRAM flush, CPU Snoop write-only, CPU SMM Mode, CPU non-SMM mode, RMU and PCIe Virtual Channels (VC0 and VC1) can have individual read/write access masks applied to them for a given memory region in Quark X1000. This enables IMRs to treat each memory transaction type listed above on an individual basis and to filter appropriately based on the IMR access mask for the memory region. Quark supports eight IMRs. Since all of the DMA capable SoC components in the X1000 are mapped to VC0 it is possible to define sections of memory as invalid for DMA write operations originating from Ethernet, USB, SD and any other DMA capable south-cluster component on VC0. Similarly it is possible to mark kernel memory as non-SMM mode read/write only or to mark BIOS runtime memory as SMM mode accessible only depending on the particular memory footprint on a given system. On an IMR violation Quark SoC X1000 systems are configured to reset the system, so ensuring that the IMR memory map is consistent with the EFI provided memory map is critical to ensure no IMR violations reset the system. The API for accessing IMRs is based on MTRR code but doesn't provide a /proc or /sys interface to manipulate IMRs. Defining the size and extent of IMRs is exclusively the domain of in-kernel code. Quark firmware sets up a series of locked IMRs around pieces of memory that firmware owns such as ACPI runtime data. During boot a series of unlocked IMRs are placed around items in memory to guarantee no DMA modification of those items can take place. Grub also places an unlocked IMR around the kernel boot params data structure and compressed kernel image. It is necessary for the kernel to tear down all unlocked IMRs in order to ensure that the kernel's view of memory passed via the EFI memory map is consistent with the IMR memory map. Without tearing down all unlocked IMRs on boot transitory IMRs such as those used to protect the compressed kernel image will cause IMR violations and system reboots. The IMR init code tears down all unlocked IMRs and sets a protective IMR around the kernel .text and .rodata as one contiguous block. This sanitizes the IMR memory map with respect to the EFI memory map and protects the read-only portions of the kernel from unwarranted DMA access. Tested-by: Ong, Boon Leong <boon.leong.ong@intel.com> Signed-off-by: Bryan O'Donoghue <pure.logic@nexus-software.ie> Reviewed-by: Andy Shevchenko <andy.schevchenko@gmail.com> Reviewed-by: Darren Hart <dvhart@linux.intel.com> Reviewed-by: Ong, Boon Leong <boon.leong.ong@intel.com> Cc: andy.shevchenko@gmail.com Cc: dvhart@infradead.org Link: http://lkml.kernel.org/r/1422635379-12476-2-git-send-email-pure.logic@nexus-software.ie Signed-off-by: Ingo Molnar <mingo@kernel.org>
339 lines
10 KiB
Text
339 lines
10 KiB
Text
menu "Kernel hacking"
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config TRACE_IRQFLAGS_SUPPORT
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def_bool y
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source "lib/Kconfig.debug"
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config STRICT_DEVMEM
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bool "Filter access to /dev/mem"
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---help---
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If this option is disabled, you allow userspace (root) access to all
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of memory, including kernel and userspace memory. Accidental
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access to this is obviously disastrous, but specific access can
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be used by people debugging the kernel. Note that with PAT support
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enabled, even in this case there are restrictions on /dev/mem
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use due to the cache aliasing requirements.
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If this option is switched on, the /dev/mem file only allows
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userspace access to PCI space and the BIOS code and data regions.
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This is sufficient for dosemu and X and all common users of
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/dev/mem.
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If in doubt, say Y.
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config X86_VERBOSE_BOOTUP
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bool "Enable verbose x86 bootup info messages"
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default y
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---help---
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Enables the informational output from the decompression stage
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(e.g. bzImage) of the boot. If you disable this you will still
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see errors. Disable this if you want silent bootup.
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config EARLY_PRINTK
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bool "Early printk" if EXPERT
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default y
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---help---
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Write kernel log output directly into the VGA buffer or to a serial
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port.
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This is useful for kernel debugging when your machine crashes very
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early before the console code is initialized. For normal operation
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it is not recommended because it looks ugly and doesn't cooperate
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with klogd/syslogd or the X server. You should normally N here,
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unless you want to debug such a crash.
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config EARLY_PRINTK_INTEL_MID
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bool "Early printk for Intel MID platform support"
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depends on EARLY_PRINTK && X86_INTEL_MID
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config EARLY_PRINTK_DBGP
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bool "Early printk via EHCI debug port"
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depends on EARLY_PRINTK && PCI
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---help---
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Write kernel log output directly into the EHCI debug port.
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This is useful for kernel debugging when your machine crashes very
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early before the console code is initialized. For normal operation
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it is not recommended because it looks ugly and doesn't cooperate
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with klogd/syslogd or the X server. You should normally N here,
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unless you want to debug such a crash. You need usb debug device.
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config EARLY_PRINTK_EFI
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bool "Early printk via the EFI framebuffer"
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depends on EFI && EARLY_PRINTK
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select FONT_SUPPORT
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---help---
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Write kernel log output directly into the EFI framebuffer.
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This is useful for kernel debugging when your machine crashes very
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early before the console code is initialized.
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config X86_PTDUMP
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bool "Export kernel pagetable layout to userspace via debugfs"
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depends on DEBUG_KERNEL
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select DEBUG_FS
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---help---
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Say Y here if you want to show the kernel pagetable layout in a
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debugfs file. This information is only useful for kernel developers
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who are working in architecture specific areas of the kernel.
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It is probably not a good idea to enable this feature in a production
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kernel.
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If in doubt, say "N"
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config EFI_PGT_DUMP
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bool "Dump the EFI pagetable"
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depends on EFI && X86_PTDUMP
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---help---
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Enable this if you want to dump the EFI page table before
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enabling virtual mode. This can be used to debug miscellaneous
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issues with the mapping of the EFI runtime regions into that
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table.
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config DEBUG_RODATA
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bool "Write protect kernel read-only data structures"
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default y
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depends on DEBUG_KERNEL
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---help---
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Mark the kernel read-only data as write-protected in the pagetables,
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in order to catch accidental (and incorrect) writes to such const
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data. This is recommended so that we can catch kernel bugs sooner.
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If in doubt, say "Y".
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config DEBUG_RODATA_TEST
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bool "Testcase for the DEBUG_RODATA feature"
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depends on DEBUG_RODATA
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default y
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---help---
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This option enables a testcase for the DEBUG_RODATA
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feature as well as for the change_page_attr() infrastructure.
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If in doubt, say "N"
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config DEBUG_SET_MODULE_RONX
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bool "Set loadable kernel module data as NX and text as RO"
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depends on MODULES
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---help---
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This option helps catch unintended modifications to loadable
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kernel module's text and read-only data. It also prevents execution
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of module data. Such protection may interfere with run-time code
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patching and dynamic kernel tracing - and they might also protect
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against certain classes of kernel exploits.
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If in doubt, say "N".
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config DEBUG_NX_TEST
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tristate "Testcase for the NX non-executable stack feature"
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depends on DEBUG_KERNEL && m
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---help---
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This option enables a testcase for the CPU NX capability
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and the software setup of this feature.
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If in doubt, say "N"
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config DOUBLEFAULT
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default y
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bool "Enable doublefault exception handler" if EXPERT
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---help---
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This option allows trapping of rare doublefault exceptions that
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would otherwise cause a system to silently reboot. Disabling this
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option saves about 4k and might cause you much additional grey
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hair.
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config DEBUG_TLBFLUSH
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bool "Set upper limit of TLB entries to flush one-by-one"
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depends on DEBUG_KERNEL
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---help---
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X86-only for now.
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This option allows the user to tune the amount of TLB entries the
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kernel flushes one-by-one instead of doing a full TLB flush. In
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certain situations, the former is cheaper. This is controlled by the
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tlb_flushall_shift knob under /sys/kernel/debug/x86. If you set it
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to -1, the code flushes the whole TLB unconditionally. Otherwise,
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for positive values of it, the kernel will use single TLB entry
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invalidating instructions according to the following formula:
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flush_entries <= active_tlb_entries / 2^tlb_flushall_shift
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If in doubt, say "N".
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config IOMMU_DEBUG
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bool "Enable IOMMU debugging"
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depends on GART_IOMMU && DEBUG_KERNEL
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depends on X86_64
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---help---
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Force the IOMMU to on even when you have less than 4GB of
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memory and add debugging code. On overflow always panic. And
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allow to enable IOMMU leak tracing. Can be disabled at boot
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time with iommu=noforce. This will also enable scatter gather
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list merging. Currently not recommended for production
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code. When you use it make sure you have a big enough
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IOMMU/AGP aperture. Most of the options enabled by this can
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be set more finegrained using the iommu= command line
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options. See Documentation/x86/x86_64/boot-options.txt for more
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details.
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config IOMMU_STRESS
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bool "Enable IOMMU stress-test mode"
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---help---
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This option disables various optimizations in IOMMU related
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code to do real stress testing of the IOMMU code. This option
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will cause a performance drop and should only be enabled for
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testing.
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config IOMMU_LEAK
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bool "IOMMU leak tracing"
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depends on IOMMU_DEBUG && DMA_API_DEBUG
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---help---
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Add a simple leak tracer to the IOMMU code. This is useful when you
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are debugging a buggy device driver that leaks IOMMU mappings.
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config HAVE_MMIOTRACE_SUPPORT
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def_bool y
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config X86_DECODER_SELFTEST
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bool "x86 instruction decoder selftest"
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depends on DEBUG_KERNEL && KPROBES
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depends on !COMPILE_TEST
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---help---
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Perform x86 instruction decoder selftests at build time.
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This option is useful for checking the sanity of x86 instruction
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decoder code.
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If unsure, say "N".
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#
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# IO delay types:
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#
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config IO_DELAY_TYPE_0X80
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int
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default "0"
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config IO_DELAY_TYPE_0XED
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int
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default "1"
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config IO_DELAY_TYPE_UDELAY
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int
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default "2"
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config IO_DELAY_TYPE_NONE
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int
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default "3"
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choice
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prompt "IO delay type"
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default IO_DELAY_0X80
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config IO_DELAY_0X80
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bool "port 0x80 based port-IO delay [recommended]"
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---help---
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This is the traditional Linux IO delay used for in/out_p.
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It is the most tested hence safest selection here.
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config IO_DELAY_0XED
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bool "port 0xed based port-IO delay"
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---help---
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Use port 0xed as the IO delay. This frees up port 0x80 which is
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often used as a hardware-debug port.
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config IO_DELAY_UDELAY
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bool "udelay based port-IO delay"
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---help---
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Use udelay(2) as the IO delay method. This provides the delay
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while not having any side-effect on the IO port space.
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config IO_DELAY_NONE
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bool "no port-IO delay"
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---help---
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No port-IO delay. Will break on old boxes that require port-IO
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delay for certain operations. Should work on most new machines.
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endchoice
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if IO_DELAY_0X80
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_0X80
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endif
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if IO_DELAY_0XED
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_0XED
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endif
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if IO_DELAY_UDELAY
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_UDELAY
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endif
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if IO_DELAY_NONE
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config DEFAULT_IO_DELAY_TYPE
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int
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default IO_DELAY_TYPE_NONE
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endif
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config DEBUG_BOOT_PARAMS
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bool "Debug boot parameters"
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depends on DEBUG_KERNEL
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depends on DEBUG_FS
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---help---
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This option will cause struct boot_params to be exported via debugfs.
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config CPA_DEBUG
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bool "CPA self-test code"
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depends on DEBUG_KERNEL
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---help---
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Do change_page_attr() self-tests every 30 seconds.
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config OPTIMIZE_INLINING
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bool "Allow gcc to uninline functions marked 'inline'"
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---help---
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This option determines if the kernel forces gcc to inline the functions
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developers have marked 'inline'. Doing so takes away freedom from gcc to
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do what it thinks is best, which is desirable for the gcc 3.x series of
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compilers. The gcc 4.x series have a rewritten inlining algorithm and
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enabling this option will generate a smaller kernel there. Hopefully
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this algorithm is so good that allowing gcc 4.x and above to make the
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decision will become the default in the future. Until then this option
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is there to test gcc for this.
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If unsure, say N.
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config DEBUG_NMI_SELFTEST
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bool "NMI Selftest"
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depends on DEBUG_KERNEL && X86_LOCAL_APIC
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---help---
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Enabling this option turns on a quick NMI selftest to verify
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that the NMI behaves correctly.
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This might help diagnose strange hangs that rely on NMI to
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function properly.
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If unsure, say N.
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config DEBUG_IMR_SELFTEST
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bool "Isolated Memory Region self test"
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default n
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depends on INTEL_IMR
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---help---
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This option enables automated sanity testing of the IMR code.
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Some simple tests are run to verify IMR bounds checking, alignment
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and overlapping. This option is really only useful if you are
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debugging an IMR memory map or are modifying the IMR code and want to
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test your changes.
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If unsure say N here.
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config X86_DEBUG_STATIC_CPU_HAS
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bool "Debug alternatives"
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depends on DEBUG_KERNEL
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---help---
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This option causes additional code to be generated which
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fails if static_cpu_has() is used before alternatives have
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run.
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If unsure, say N.
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endmenu
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