[PATCH] schemas: Add schema for firmware logs
Peter Robinson
pbrobinson at gmail.com
Sat Feb 4 10:35:50 CET 2023
Hi Simon,
Does it make sense to devise something that is compatible with the
kernel's pstore [1] mechanism?
Peter
[1] https://lwn.net/Articles/434821/
On Sat, Feb 4, 2023 at 12:20 AM Simon Glass <sjg at chromium.org> wrote:
>
> A common way to detect problems in firmware is to collect logs from
> the firmware, then pass them to the OS for storage and analysis.
>
> Logs can take the form of simple text output, or structured logs where the
> filename and line number, etc. are provided. Timestamps can sometimes be
> useful, too.
>
> Ideally the log can be displayed as simple ASCII without always needing
> a special program to read it.
>
> The firmware consists of various boot phases, any of which can contribute
> log information. It is assumed that these logs are not interleaved, i.e.
> that the phases run one after the other.
>
> The final boot phase (before the OS) is responsible for collecting the
> logs, e.g. from a Transfer List, and placing them in the devicetree.
>
> This binding collects the logs as individual log at n subnodes within a
> /chosen/logs node.
>
> If firmware phases use the devicetree to pass logs between each other,
> then the /chosen node should still be used. The /options node is not
> supported. Subsequent phases must be sure to use the next numbered
> log at n node.
>
> If the log data is sitting in memory somewhere, it is possible to point
> to it, rather than copying the data into a property. For large logs this
> may be more efficient. It must end with a NUL character, so the total
> space for actual log data is one byte less than the allocated size.
>
> If something goes wrong and an incomplete log record is emitted, then the
> next record may appear to be part of it, since there is no LF or ETX
> character at the end of the previous record.
>
> The intent with this binding is to provide a Linux driver which can
> provide access to the log data after booting is complete.
>
> Other things not considered:
> - signalling overflow of a log buffer
> - circular log buffers
> - a single unified log buffer with inline ASCII characters to indicate the
> phase and project
> - log records that contain multiple lines of text
>
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
>
> dtschema/schemas/chosen.yaml | 3 +
> dtschema/schemas/log.yaml | 176 +++++++++++++++++++++++++++++++++++
> dtschema/schemas/logs.yaml | 30 ++++++
> test/logs.dts | 47 ++++++++++
> 4 files changed, 256 insertions(+)
> create mode 100644 dtschema/schemas/log.yaml
> create mode 100644 dtschema/schemas/logs.yaml
> create mode 100644 test/logs.dts
>
> diff --git a/dtschema/schemas/chosen.yaml b/dtschema/schemas/chosen.yaml
> index 86194dd..46cc9fb 100644
> --- a/dtschema/schemas/chosen.yaml
> +++ b/dtschema/schemas/chosen.yaml
> @@ -236,6 +236,9 @@ properties:
> system.
>
> patternProperties:
> + '^logs$':
> + $ref: logs.yaml#
> +
> "^framebuffer": true
>
> additionalProperties: false
> diff --git a/dtschema/schemas/log.yaml b/dtschema/schemas/log.yaml
> new file mode 100644
> index 0000000..5218234
> --- /dev/null
> +++ b/dtschema/schemas/log.yaml
> @@ -0,0 +1,176 @@
> +# SPDX-License-Identifier: BSD-2-Clause
> +# Copyright 2023 Google LLC
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/log.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Log-output binding
> +
> +maintainers:
> + - Simon Glass <sjg at chromium.org>
> +
> +description:
> + This holds a log file or console dump created by a single phase of the boot.
> + It typically consists of plain ASCII text, but it is also possible to
> + add metadata like files and line numbers.
> +
> + Each log node has a hex unit address which indicates the order of progress
> + through the boot phases. The first node must be log at 0, followed by
> + log at 1, etc.
> +
> +select: false
> +
> +properties:
> + reg:
> + description:
> + Defines a unique log ID for the log represented by the log node.
> +
> + boot-phase:
> + $ref: types.yaml#/definitions/string
> + description: |
> + Indicates the phase of boot which produced this log:
> +
> + - pre-sram: Before SRAM is available
> + - verify: Verification step, which decides which of the available images
> + should be run next
> + - pre-ram: Sets up SDRAM
> + - some-ram: After SDRAM is working but before all of it is available.
> + Some RAM is available but it is limited (e.g. it may be split into
> + two pieces by the location of the running program) because the
> + program code is not yet relocated out of the way.
> + - loader: OS loader, typically the final firmware step
> +
> + pattern: "^pre-sram|verify|pre-ram|some-ram|loader$"
> +
> + project:
> + $ref: types.yaml#/definitions/string
> + description:
> + Indicates the name of the project which produced this log
> +
> + pattern: "^U-Boot|TF-A"
> +
> + time-format:
> + $ref: types.yaml#/definitions/string
> + description: |
> + Indicates the time format used by the log. Options are:
> +
> + usec - a integer number of microseconds since reset was released,
> + expressed in ASCII, e.g. "123"
> +
> + pattern: "^usec$"
> +
> + text-start:
> + oneOf:
> + - $ref: types.yaml#/definitions/uint32
> + - $ref: types.yaml#/definitions/uint64
> + description:
> + These properties hold the physical start and end address of the log text
> + if the 'text' property is not used.
> +
> + Note that text-start is inclusive, but text-end is exclusive.
> +
> + The text must be terminated with a NUL character.
> +
> + text-end:
> + oneOf:
> + - $ref: types.yaml#/definitions/uint32
> + - $ref: types.yaml#/definitions/uint64
> + description:
> + These properties hold the physical start and end address of the log text
> + if the 'text' property is not used.
> +
> + Note that text-start is inclusive, but text-end is exclusive.
> +
> + The text must be terminated with a NUL character.
> +
> + text:
> + $ref: types.yaml#/definitions/string
> + description: |
> + Contains the log text, if it is not referred to by text-start / text-end.
> +
> + The format is ASCII with US and SOT used to indicate optional fields:
> +
> + [timestamp<US>][level[:category[:filename[:line[:function]]]]]<SOT>]message[<LF>|<ETX>]
> +
> + where:
> +
> + timestamp is the timestamp, according to time-format
> +
> + level is the single-digit log level:
> + 0 - emergency (program is unstable)
> + 1 - alert (action must be taken immediately)
> + 2 - crit (critical conditions)
> + 3 - err (error that prevents something from working
> + 4 - warning (may prevent optimal operation)
> + 5 - notice (normal but significant condition, printf())
> + 6 - info (general information message)
> + 7 - debug (basic debug-level message)
> + 8 - debug content (debug message showing full message content)
> + 9 - debug I/O (debug message showing hardware I/O access)
> +
> + category is the category name which is project-dependent
> +
> + filename is the relative filename (__FILE__ in C)
> +
> + line is the line number starting from 1 (__LINE__ in C)
> +
> + function is the function name (__func__ in C)
> +
> + message is the message string, which may not contain control
> + characters (beyond those listed above) except for HT and LF. DEL and CR
> + are not permitted.
> +
> + The timestamp is present only if US is in the string.
> +
> + The fields before <SOT> are all optional, but must be listed in order.
> + To omit a field in the middle, use an empty string between two colons.
> + To omit a field at the end, just leave it out along with the colon before
> + it.
> +
> + Typically LF is used as a line delimiter, but if a record does not
> + end with a newline, ETX can be used. This indicates that it is a new
> + log record but without a newline between them. Often (but not always)
> + the 'continuation' does not include the US and SOT information.
> +
> + A log record without a LF or ETX terminator is considered invalid, even
> + if it is the final record.
> +
> + Examples:
> +
> + 123<US>5:tpm:lib/tpm.c:334:tpm_init<SOT>TPM starting...<LF>
> + 23<US>Hello<LF>
> + 2:boot:lib/panic.c:84:panic<SOT>Memory training failed<LF>
> + 7:mmc:::mmc_bind<SOT>Cannot create block device<LF>
> + Net: eth0: host_lo, eth1: host_enp1s0<ETX>
> +
> + ASCII characters:
> +
> + SOT - 0x2 - indicates the start of the message. This is optional if
> + the record has nothing but a message
> + ETX - 0x3 - indicates the end of a log record (without new line)
> + LF - 0xa - indicates the end of a log record (and new line)
> + US - 0x1f - indicates the end of the timestamp (and that it is present
> + in the record)
> +
> + The above format is intended to be unambiguous, while still being fairly
> + readable it just shown on a terminal with all control characters except
> + LF dropped. The CR character is not permitted since it is not needed to
> + signal an end of line and it avoids worrying about what <CR><LF> actually
> + means.
> +
> + The text size is determined by the property size. The last byte must be
> + a NUL character.
> +
> +required:
> + - boot-phase
> + - project
> +
> +anyOf:
> + - required:
> + - text
> + - required:
> + - text-start
> + - text-end
> +
> +additionalProperties: false
> diff --git a/dtschema/schemas/logs.yaml b/dtschema/schemas/logs.yaml
> new file mode 100644
> index 0000000..76ba2b0
> --- /dev/null
> +++ b/dtschema/schemas/logs.yaml
> @@ -0,0 +1,30 @@
> +# SPDX-License-Identifier: BSD-2-Clause
> +# Copyright 2023 Google LLC
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/logs.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Log information collected during firmware execution
> +
> +maintainers:
> + - Simon Glass <sjg at chromium.org>
> +
> +description:
> + This holds a set of logs build up during booting of the machine. The
> + collection of logs is described in the "/logs" node. This node in turn
> + contains a number of subnodes representing individual log output from
> + different boot phases.
> +
> +properties:
> + '#address-cells':
> + const: 1
> +
> + '#size-cells':
> + const: 0
> +
> +patternProperties:
> + '^log@[0-9a-f]+$':
> + $ref: log.yaml#
> +
> +additionalProperties: false
> diff --git a/test/logs.dts b/test/logs.dts
> new file mode 100644
> index 0000000..7d044df
> --- /dev/null
> +++ b/test/logs.dts
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: BSD-2-Clause
> +// Copyright 2023 Google LLC
> +
> +// Used to validate the "logs" node and its child "log" nodes
> +
> +// dtc -O dtb -o test.dtb test/bootphases.dts && tools/dt-validate -s test/schemas -m test.dtb
> +
> +
> +/dts-v1/;
> +
> +/ {
> + model = "none";
> + compatible = "foo";
> +
> + #address-cells = <1>;
> + #size-cells = <1>;
> +
> + chosen {
> + logs {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + log at 0 {
> + reg = <0>;
> + boot-phase = "pre-ram";
> + project = "U-Boot";
> + text = "\nU-Boot SPL 2023.01 (Feb 03 2023 - 14:45:39 -0700)\nTrying to boot from sandbox_image\nTrying to boot from sandbox_file\n";
> + };
> +
> + log at 1 {
> + reg = <1>;
> + boot-phase = "loader";
> + project = "U-Boot";
> + time-format = "usec";
> + text = "\n\n123\x1f2:boot:lib/display_options.c:43:display_options\x02U-Boot 2023.01 (Feb 03 2023 - 14:45:39 -0700)\n\nReset Status: COLD\nModel: sandbox\nDRAM: 256 MiB\n";
> + };
> +
> + log at 2 {
> + reg = <2>;
> + boot-phase = "pre-ram";
> + project = "TF-A";
> + text-start = <0x103000>;
> + text-end = <0x107000>;
> + };
> + };
> + };
> +};
> --
> 2.39.1.519.gcb327c4b5f-goog
>
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