On 2023-12-20 08:52, Csókás Bence wrote:
On 2023. 12. 20. 8:09, Dragan Simic wrote:
On 2023-12-20 07:49, Csókás Bence wrote:
On 2023. 12. 19. 21:33, Daniel Golle wrote:
What comes to mind is that CONFIG_CONSOLE_RECORD also captures ANSI
sequences during menu or count-down before boot, so we'd have to
either
introduce a dedicated log_printf() call and use that when ever we
want
the output to also become part of the log buffer or we could somehow
filter the recorded console, eliminating all terminal control
sequences.
I don't think that would be a huge problem, Linux userspace can
filter
ANSI control codes if it wants to. For now, I'd like a byte-for-byte
copy of the console, as-is, presented to Linux.
But wouldn't recording the control sequences as-is actually be pretty
much useless? For example, some user can spend a few minutes
scrolling through the boot menu, which would produce a fair amount of
nearly useless recorded data.
Moreover, if I'm not wrong, viewing or parsing such as-is data would
actually require replaying the control sequences, to reproduce the
actual console contents as it was recorded, which would be quite
cumbersome.
It *is* useless, but most of the times the user won't be scrolling at
all anyways, that's why I don't think these few extra bytes would be a
problem.
Quite frankly, when it comes to computing in general, taking the "ah, it
probably won't happen" approach isn't the best thing to do. We should
aim toward covering properly even the edge cases, if you agree.
And no, you don't need anything to "process" ANSI codes, you can just
`cat` them and your terminal will parse it anyways.
In that case, you'd probably see only the end results of the control
sequences, which makes logging them as-is quite pointless. To see what
actually happened on the U-Boot console, you'd need to execute the
control sequences step by step and watch the results.
As I undersand (never used it before, just quickly read the kernel
doc),
PStore is for Linux -> U-Boot communication. What I'm doing is the
opposite. But the approach I envisioned is similar: make U-Boot save
a
copy of the log to a struct at a fixed memory address, then pass this
address + the length of the log to the kernel via DT and/or
commandline.
Actually, pstore is primarily intended as a means to record and store
kernel crash dumps for later investigation. In other words, the
kernel writes data to pstore during an oops so it can be investigated
later.
One of the benefits of using pstore for record the U-Boot console
contents, instead of using a memory region, is that no special
utilities would be required to access the recorded console outputs.
Also, many of the requirements that you listed below would be already
fulfilled.
What I thought to include in the struct:
* magic cookie (it was in the 3rd party solution, and it's an easy
way
of doing some form of integrity check)
* struct version (in case we ever change the layout)
* U-Boot version code (maybe not necessary? It can be parsed out of
the
log as well)
* length of the log (or it could also be passed via DT/cmdline)
* and then the log buffer of course
That's what I read as well. Is there support for U-boot to write and
Linux to read PStores?
No and yes, but U-Boot can already read pstore. Please see
doc/usage/cmd/pstore.rst for the U-Boot part, and
Documentation/admin-guide/pstore-blk.rst for the Linux kernel part.
Another benefit of using pstore would be no permanently wasted RAM for
the recorded console contents. Also, having the data recorded to a
storage device also goes along with providing permanent records.
