main: Address strncat() overflow warning

```
FAILED: debug-trigger.p/main.c.o
ccache cc -Idebug-trigger.p -I. -I.. -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -Wped

main: Address strncat() overflow warning

```
FAILED: debug-trigger.p/main.c.o
ccache cc -Idebug-trigger.p -I. -I.. -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -Wpedantic -Werror -std=gnu18 -O0 -g -MD -MQ debug-trigger.p/main.c.o -MF debug-trigger.p/main.c.o.d -o debug-trigger.p/main.c.o -c ../main.c
../main.c: In function ‘main’:
../main.c:549:17: error: ‘strncat’ specified bound 4096 equals destination size [-Werror=stringop-overflow=]
549 | strncat(devnode, devid, sizeof(devnode));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
```

Change-Id: Id9abfb900ad7601acd595febf00eb92c5a56d3af
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>

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main: Log command read from source

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ifeec81b37768052cabed63ff814499c8972817e1

main: Be clear about what we failed to open

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I5884b83716f73da8f055a7267b3efab36c856ea8

main: Add a 'dbus' set of sink actions

The sysrq sink actions are are intended for use with kdump, which will
capture relevant kernel and userspace memory. It's implementation is
thus pretty straigh

main: Add a 'dbus' set of sink actions

The sysrq sink actions are are intended for use with kdump, which will
capture relevant kernel and userspace memory. It's implementation is
thus pretty straight forward.

Most BMCs don't use kdump, so implement a set of sink actions that talk
via D-Bus to generate a dump and gracefully reboot the BMC.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I126b0118faaa793011268a785eeb955139739eaf

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main: Extract a 'source' abstraction

The D-Bus set of sink actions will require polling the D-Bus fd and
processing any inbound messages. To do this, the polling must happen
where we're currently re

main: Extract a 'source' abstraction

The D-Bus set of sink actions will require polling the D-Bus fd and
processing any inbound messages. To do this, the polling must happen
where we're currently reading from the source file descriptor. In the
same manner as the sink abstraction extract a source abstraction to hide
the details. process() is then implemented in terms of the abstract
source interface.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I629e0d71f30592fa30affac1a920104e8086d8b0

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main: Add --sink-actions=... command-line option

Allow explicit configuration of the actions to take when a valid command
is received from the source. This patch gives the current set of actions
the

main: Add --sink-actions=... command-line option

Allow explicit configuration of the actions to take when a valid command
is received from the source. This patch gives the current set of actions
the name 'sysrq'.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ie8e7446599edb5927468865bcea36b596aef12f6

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main: Extract a 'sink' abstraction

In the future we'll add a set of sink actions that call through D-Bus to
generate a BMC dump and do a graceful reboot rather than crashing the
system through /proc

main: Extract a 'sink' abstraction

In the future we'll add a set of sink actions that call through D-Bus to
generate a BMC dump and do a graceful reboot rather than crashing the
system through /proc/sysrq-trigger. Reorganise the code so the process()
function operates on abstract sink types. This way we can encapsulate
the D-Bus specifics in a way that doesn't affect the process()
implementation.

Concretely, there are two actions that can be triggered by the source,
'debug' and 'reboot'. Add the same as callbacks on the sink structure
and implement the 'sysrq' behaviours in terms of the new abstraction.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ic62348365e9d0f13abbdcd81848bc4ca344135ee

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main: Add some documentation

Some tricks like defaulting the source and sink file descriptors to
stdin and stdout aren't necessarily obvious, so add some commentary and
justifications throughout.

S

main: Add some documentation

Some tricks like defaulting the source and sink file descriptors to
stdin and stdout aren't necessarily obvious, so add some commentary and
justifications throughout.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I515f36857a7056aa589ecbb09c46372ec4d3976d

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main: Use /proc/sysrq-trigger for reboot as well as crash

This way when using stdout as the sink we don't accidentally reboot the
system.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id:

main: Use /proc/sysrq-trigger for reboot as well as crash

This way when using stdout as the sink we don't accidentally reboot the
system.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: If6b08f7a2773debf10bd1439790f8f9c83604d59

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process: Lift reboot implementation to separate function

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I400d923781b3dd434dc51178c4dc9a8be6d3408f

process: Lift debug implementation to separate function

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I8f4ed09dfd8a0f034678530e6fc9799d2c8f34b6

debug-trigger: Do what we can to debug unresponsive systems

debug-trigger is a small daemon which translates an external signal that
the system is unresponsive into a system crash for debug data
col

debug-trigger: Do what we can to debug unresponsive systems

debug-trigger is a small daemon which translates an external signal that
the system is unresponsive into a system crash for debug data
collection.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: Ic04f1a95aaf651d56b75f5261d8a6f76d34477a7

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