9d843e8faf
There could be a scenario where we define some region in normal memory and use them store to logs which is later retrieved by bootloader during warm reset. In this scenario, we wanted to treat this memory as normal cacheable memory instead of default behaviour which is an overhead. Making it cacheable could improve performance. This commit gives control to change mem_type from Device tree, and also documents the value for normal memory. Signed-off-by: Mukesh Ojha <mojha@codeaurora.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/1616438537-13719-1-git-send-email-mojha@codeaurora.org
67 lines
2.6 KiB
Plaintext
67 lines
2.6 KiB
Plaintext
Ramoops oops/panic logger
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=========================
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ramoops provides persistent RAM storage for oops and panics, so they can be
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recovered after a reboot. This is a child-node of "/reserved-memory", and
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is named "ramoops" after the backend, rather than "pstore" which is the
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subsystem.
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Parts of this storage may be set aside for other persistent log buffers, such
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as kernel log messages, or for optional ECC error-correction data. The total
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size of these optional buffers must fit in the reserved region.
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Any remaining space will be used for a circular buffer of oops and panic
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records. These records have a configurable size, with a size of 0 indicating
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that they should be disabled.
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At least one of "record-size", "console-size", "ftrace-size", or "pmsg-size"
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must be set non-zero, but are otherwise optional as listed below.
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Required properties:
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- compatible: must be "ramoops"
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- reg: region of memory that is preserved between reboots
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Optional properties:
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- ecc-size: enables ECC support and specifies ECC buffer size in bytes
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(defaults to 0: no ECC)
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- record-size: maximum size in bytes of each kmsg dump.
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(defaults to 0: disabled)
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- console-size: size in bytes of log buffer reserved for kernel messages
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(defaults to 0: disabled)
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- ftrace-size: size in bytes of log buffer reserved for function tracing and
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profiling (defaults to 0: disabled)
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- pmsg-size: size in bytes of log buffer reserved for userspace messages
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(defaults to 0: disabled)
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- mem-type: if present, sets the type of mapping is to be used to map the
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reserved region. mem-type: 0 = write-combined (default), 1 = unbuffered,
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2 = cached.
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- unbuffered: deprecated, use mem_type instead. If present, and mem_type is
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not specified, it is equivalent to mem_type = 1 and uses unbuffered mappings
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to map the reserved region (defaults to buffered mappings mem_type = 0). If
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both are specified -- "mem_type" overrides "unbuffered".
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- max-reason: if present, sets maximum type of kmsg dump reasons to store
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(defaults to 2: log Oopses and Panics). This can be set to INT_MAX to
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store all kmsg dumps. See include/linux/kmsg_dump.h KMSG_DUMP_* for other
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kmsg dump reason values. Setting this to 0 (KMSG_DUMP_UNDEF), means the
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reason filtering will be controlled by the printk.always_kmsg_dump boot
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param: if unset, it will be KMSG_DUMP_OOPS, otherwise KMSG_DUMP_MAX.
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- no-dump-oops: deprecated, use max_reason instead. If present, and
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max_reason is not specified, it is equivalent to max_reason = 1
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(KMSG_DUMP_PANIC).
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- flags: if present, pass ramoops behavioral flags (defaults to 0,
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see include/linux/pstore_ram.h RAMOOPS_FLAG_* for flag values).
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