b9a3899d59
Hardware errors on the Blackfin architecture are queued by nature of the hardware design. Things that could generate a hardware level queue up at the system interface and might not process until much later, at which point the system would send a notification back to the core. As such, it is possible for user space code to do something that would trigger a hardware error, but have it delay long enough for the process context to switch. So when the hardware error does signal, we mistakenly evaluate it as a different process or as kernel context and panic (erp!). This makes it pretty difficult to find the offending context. But wait, there is good news somewhere. By forcing a SSYNC in the interrupt entry, we force all pending queues at the system level to be processed and all hardware errors to be signaled. Then we check the current interrupt state to see if the hardware error is now signaled. If so, we re-queue the current interrupt and return thus allowing the higher priority hardware error interrupt to process properly. Since we haven't done any other context processing yet, the right context will be selected and killed. There is still the possibility that the exact offending instruction will be unknown, but at least we'll have a much better idea of where to look. The downside of course is that this causes system-wide syncs at every interrupt point which results in significant performance degradation. Since this situation should not occur in any properly configured system (as hardware errors are triggered by things like bad pointers), make it a debug configuration option and disable it by default. Signed-off-by: Robin Getz <robin.getz@analog.com> Signed-off-by: Mike Frysinger <vapier@gentoo.org>
256 lines
8.7 KiB
Plaintext
256 lines
8.7 KiB
Plaintext
menu "Kernel hacking"
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source "lib/Kconfig.debug"
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config DEBUG_STACKOVERFLOW
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bool "Check for stack overflows"
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depends on DEBUG_KERNEL
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help
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This option will cause messages to be printed if free stack space
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drops below a certain limit.
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config DEBUG_STACK_USAGE
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bool "Enable stack utilization instrumentation"
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depends on DEBUG_KERNEL
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help
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Enables the display of the minimum amount of free stack which each
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task has ever had available in the sysrq-T output.
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This option will slow down process creation somewhat.
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config HAVE_ARCH_KGDB
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def_bool y
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config DEBUG_VERBOSE
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bool "Verbose fault messages"
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default y
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select PRINTK
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help
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When a program crashes due to an exception, or the kernel detects
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an internal error, the kernel can print a not so brief message
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explaining what the problem was. This debugging information is
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useful to developers and kernel hackers when tracking down problems,
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but mostly meaningless to other people. This is always helpful for
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debugging but serves no purpose on a production system.
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Most people should say N here.
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config DEBUG_MMRS
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bool "Generate Blackfin MMR tree"
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select DEBUG_FS
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help
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Create a tree of Blackfin MMRs via the debugfs tree. If
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you enable this, you will find all MMRs laid out in the
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/sys/kernel/debug/blackfin/ directory where you can read/write
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MMRs directly from userspace. This is obviously just a debug
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feature.
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config DEBUG_HWERR
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bool "Hardware error interrupt debugging"
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depends on DEBUG_KERNEL
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help
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When enabled, the hardware error interrupt is never disabled, and
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will happen immediately when an error condition occurs. This comes
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at a slight cost in code size, but is necessary if you are getting
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hardware error interrupts and need to know where they are coming
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from.
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config EXACT_HWERR
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bool "Try to make Hardware errors exact"
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depends on DEBUG_HWERR
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help
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By default, the Blackfin hardware errors are not exact - the error
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be reported multiple cycles after the error happens. This delay
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can cause the wrong application, or even the kernel to receive a
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signal to be killed. If you are getting HW errors in your system,
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try turning this on to ensure they are at least comming from the
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proper thread.
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On production systems, it is safe (and a small optimization) to say N.
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config DEBUG_DOUBLEFAULT
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bool "Debug Double Faults"
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default n
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help
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If an exception is caused while executing code within the exception
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handler, the NMI handler, the reset vector, or in emulator mode,
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a double fault occurs. On the Blackfin, this is a unrecoverable
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event. You have two options:
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- RESET exactly when double fault occurs. The excepting
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instruction address is stored in RETX, where the next kernel
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boot will print it out.
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- Print debug message. This is much more error prone, although
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easier to handle. It is error prone since:
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- The excepting instruction is not committed.
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- All writebacks from the instruction are prevented.
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- The generated exception is not taken.
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- The EXCAUSE field is updated with an unrecoverable event
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The only way to check this is to see if EXCAUSE contains the
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unrecoverable event value at every exception return. By selecting
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this option, you are skipping over the faulting instruction, and
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hoping things stay together enough to print out a debug message.
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This does add a little kernel code, but is the only method to debug
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double faults - if unsure say "Y"
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choice
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prompt "Double Fault Failure Method"
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default DEBUG_DOUBLEFAULT_PRINT
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depends on DEBUG_DOUBLEFAULT
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config DEBUG_DOUBLEFAULT_PRINT
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bool "Print"
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config DEBUG_DOUBLEFAULT_RESET
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bool "Reset"
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endchoice
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config DEBUG_ICACHE_CHECK
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bool "Check Instruction cache coherency"
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depends on DEBUG_KERNEL
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depends on DEBUG_HWERR
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help
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Say Y here if you are getting weird unexplained errors. This will
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ensure that icache is what SDRAM says it should be by doing a
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byte wise comparison between SDRAM and instruction cache. This
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also relocates the irq_panic() function to L1 memory, (which is
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un-cached).
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config DEBUG_HUNT_FOR_ZERO
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bool "Catch NULL pointer reads/writes"
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default y
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help
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Say Y here to catch reads/writes to anywhere in the memory range
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from 0x0000 - 0x0FFF (the first 4k) of memory. This is useful in
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catching common programming errors such as NULL pointer dereferences.
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Misbehaving applications will be killed (generate a SEGV) while the
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kernel will trigger a panic.
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Enabling this option will take up an extra entry in CPLB table.
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Otherwise, there is no extra overhead.
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config DEBUG_BFIN_HWTRACE_ON
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bool "Turn on Blackfin's Hardware Trace"
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default y
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help
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All Blackfins include a Trace Unit which stores a history of the last
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16 changes in program flow taken by the program sequencer. The history
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allows the user to recreate the program sequencer’s recent path. This
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can be handy when an application dies - we print out the execution
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path of how it got to the offending instruction.
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By turning this off, you may save a tiny amount of power.
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choice
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prompt "Omit loop Tracing"
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default DEBUG_BFIN_HWTRACE_COMPRESSION_OFF
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depends on DEBUG_BFIN_HWTRACE_ON
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help
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The trace buffer can be configured to omit recording of changes in
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program flow that match either the last entry or one of the last
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two entries. Omitting one of these entries from the record prevents
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the trace buffer from overflowing because of any sort of loop (for, do
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while, etc) in the program.
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Because zero-overhead Hardware loops are not recorded in the trace buffer,
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this feature can be used to prevent trace overflow from loops that
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are nested four deep.
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config DEBUG_BFIN_HWTRACE_COMPRESSION_OFF
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bool "Trace all Loops"
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help
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The trace buffer records all changes of flow
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config DEBUG_BFIN_HWTRACE_COMPRESSION_ONE
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bool "Compress single-level loops"
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help
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The trace buffer does not record single loops - helpful if trace
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is spinning on a while or do loop.
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config DEBUG_BFIN_HWTRACE_COMPRESSION_TWO
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bool "Compress two-level loops"
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help
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The trace buffer does not record loops two levels deep. Helpful if
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the trace is spinning in a nested loop
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endchoice
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config DEBUG_BFIN_HWTRACE_COMPRESSION
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int
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depends on DEBUG_BFIN_HWTRACE_ON
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default 0 if DEBUG_BFIN_HWTRACE_COMPRESSION_OFF
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default 1 if DEBUG_BFIN_HWTRACE_COMPRESSION_ONE
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default 2 if DEBUG_BFIN_HWTRACE_COMPRESSION_TWO
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config DEBUG_BFIN_HWTRACE_EXPAND
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bool "Expand Trace Buffer greater than 16 entries"
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depends on DEBUG_BFIN_HWTRACE_ON
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default n
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help
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By selecting this option, every time the 16 hardware entries in
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the Blackfin's HW Trace buffer are full, the kernel will move them
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into a software buffer, for dumping when there is an issue. This
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has a great impact on performance, (an interrupt every 16 change of
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flows) and should normally be turned off, except in those nasty
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debugging sessions
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config DEBUG_BFIN_HWTRACE_EXPAND_LEN
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int "Size of Trace buffer (in power of 2k)"
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range 0 4
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depends on DEBUG_BFIN_HWTRACE_EXPAND
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default 1
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help
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This sets the size of the software buffer that the trace information
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is kept in.
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0 for (2^0) 1k, or 256 entries,
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1 for (2^1) 2k, or 512 entries,
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2 for (2^2) 4k, or 1024 entries,
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3 for (2^3) 8k, or 2048 entries,
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4 for (2^4) 16k, or 4096 entries
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config DEBUG_BFIN_NO_KERN_HWTRACE
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bool "Turn off hwtrace in CPLB handlers"
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depends on DEBUG_BFIN_HWTRACE_ON
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default y
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help
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The CPLB error handler contains a lot of flow changes which can
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quickly fill up the hardware trace buffer. When debugging crashes,
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the hardware trace may indicate that the problem lies in kernel
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space when in reality an application is buggy.
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Say Y here to disable hardware tracing in some known "jumpy" pieces
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of code so that the trace buffer will extend further back.
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config EARLY_PRINTK
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bool "Early printk"
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default n
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select SERIAL_CORE_CONSOLE
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help
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This option enables special console drivers which allow the kernel
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to print messages very early in the bootup process.
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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. After enabling this
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feature, you must add "earlyprintk=serial,uart0,57600" to the
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command line (bootargs). It is safe to say Y here in all cases, as
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all of this lives in the init section and is thrown away after the
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kernel boots completely.
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config CPLB_INFO
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bool "Display the CPLB information"
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help
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Display the CPLB information via /proc/cplbinfo.
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config ACCESS_CHECK
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bool "Check the user pointer address"
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default y
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help
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Usually the pointer transfer from user space is checked to see if its
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address is in the kernel space.
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Say N here to disable that check to improve the performance.
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endmenu
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