a7a6f92544
This patch introduces a new Kconfig option which, when enabled, causes the kernel to write the PID of the current task into the PROCID field of the CONTEXTIDR on context switch. This is useful when analysing hardware trace, since writes to this register can be configured to emit an event into the trace stream. The thread notifier for writing the PID is deliberately kept separate from the ASID code, so that we can easily support newer processors (A15 onwards) which store the ASID in TTBR0. As such, the switch_mm code is updated to perform a read-modify-write sequence to ensure that we don't clobber the PID on older CPUs. Change-Id: I7236834cf4b5e984c9d9f24ba6b872078c2b936f Cc: Wolfgang Betz <wolfgang.betz@st.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Jeff Ohlstein <johlstei@codeaurora.org>
142 lines
4.8 KiB
Plaintext
142 lines
4.8 KiB
Plaintext
menu "Kernel hacking"
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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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depends on MMU
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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.
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If this option is switched on, the /dev/mem file only allows
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userspace access to memory mapped peripherals.
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If in doubt, say Y.
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# RMK wants arm kernels compiled with frame pointers or stack unwinding.
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# If you know what you are doing and are willing to live without stack
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# traces, you can get a slightly smaller kernel by setting this option to
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# n, but then RMK will have to kill you ;).
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config FRAME_POINTER
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bool
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depends on !THUMB2_KERNEL
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default y if !ARM_UNWIND || FUNCTION_GRAPH_TRACER
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help
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If you say N here, the resulting kernel will be slightly smaller and
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faster. However, if neither FRAME_POINTER nor ARM_UNWIND are enabled,
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when a problem occurs with the kernel, the information that is
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reported is severely limited.
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config ARM_UNWIND
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bool "Enable stack unwinding support (EXPERIMENTAL)"
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depends on AEABI && EXPERIMENTAL
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default y
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help
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This option enables stack unwinding support in the kernel
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using the information automatically generated by the
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compiler. The resulting kernel image is slightly bigger but
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the performance is not affected. Currently, this feature
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only works with EABI compilers. If unsure say Y.
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config OLD_MCOUNT
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bool
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depends on FUNCTION_TRACER && FRAME_POINTER
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default y
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config DEBUG_USER
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bool "Verbose user fault messages"
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help
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When a user program crashes due to an exception, the kernel can
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print a brief message explaining what the problem was. This is
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sometimes helpful for debugging but serves no purpose on a
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production system. Most people should say N here.
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In addition, you need to pass user_debug=N on the kernel command
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line to enable this feature. N consists of the sum of:
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1 - undefined instruction events
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2 - system calls
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4 - invalid data aborts
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8 - SIGSEGV faults
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16 - SIGBUS faults
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# These options are only for real kernel hackers who want to get their hands dirty.
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config DEBUG_LL
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bool "Kernel low-level debugging functions"
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depends on DEBUG_KERNEL
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help
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Say Y here to include definitions of printascii, printch, printhex
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in the kernel. This is helpful if you are debugging code that
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executes before the console is initialized.
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config EARLY_PRINTK
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bool "Early printk"
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depends on DEBUG_LL
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help
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Say Y here if you want to have an early console using the
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kernel low-level debugging functions. Add earlyprintk to your
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kernel parameters to enable this console.
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config DEBUG_ICEDCC
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bool "Kernel low-level debugging via EmbeddedICE DCC channel"
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depends on DEBUG_LL
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help
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Say Y here if you want the debug print routines to direct their
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output to the EmbeddedICE macrocell's DCC channel using
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co-processor 14. This is known to work on the ARM9 style ICE
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channel and on the XScale with the PEEDI.
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It does include a timeout to ensure that the system does not
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totally freeze when there is nothing connected to read.
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config OC_ETM
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bool "On-chip ETM and ETB"
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select ARM_AMBA
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help
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Enables the on-chip embedded trace macrocell and embedded trace
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buffer driver that will allow you to collect traces of the
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kernel code.
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config DEBUG_DC21285_PORT
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bool "Kernel low-level debugging messages via footbridge serial port"
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depends on DEBUG_LL && FOOTBRIDGE
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help
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Say Y here if you want the debug print routines to direct their
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output to the serial port in the DC21285 (Footbridge). Saying N
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will cause the debug messages to appear on the first 16550
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serial port.
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config DEBUG_CLPS711X_UART2
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bool "Kernel low-level debugging messages via UART2"
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depends on DEBUG_LL && ARCH_CLPS711X
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help
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Say Y here if you want the debug print routines to direct their
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output to the second serial port on these devices. Saying N will
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cause the debug messages to appear on the first serial port.
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config DEBUG_S3C_UART
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depends on PLAT_SAMSUNG
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int "S3C UART to use for low-level debug"
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default "0"
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help
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Choice for UART for kernel low-level using S3C UARTS,
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should be between zero and two. The port must have been
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initialised by the boot-loader before use.
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The uncompressor code port configuration is now handled
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by CONFIG_S3C_LOWLEVEL_UART_PORT.
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config PID_IN_CONTEXTIDR
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bool "Write the current PID to the CONTEXTIDR register"
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depends on CPU_COPY_V6
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help
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Enabling this option causes the kernel to write the current PID to
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the PROCID field of the CONTEXTIDR register, at the expense of some
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additional instructions during context switch. Say Y here only if you
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are planning to use hardware trace tools with this kernel.
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endmenu
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