Add tracing of interactions between the SCLP base driver, firmware and
other drivers to support problem determination in case of SCLP-related
issues.

For that purpose this patch introduces two new s390dbf debug areas:

  - sclp: An abbreviated log of all common interactions
  - sclp_err: A full log of failed or abnormal interactions

Tracing of full SCCB contents can be enabled for the sclp area by
setting its debug level to maximum (6).

Overview of added trace events:

  * Firmware interaction:
    - SRV1: Service call about to be issued
    - SRV2: Service call was issued
    - INT:  Interrupt received

  * Driver interaction:
    - RQAD: Request was added
    - RQOK: Request success
    - RQAB: Request aborted
    - RQTM: Request timed out
    - REG:  Event listener registered
    - UREG: Event listener unregistered
    - EVNT: Event callback
    - STCG: State-change callback

  * Abnormal events:
    - TMO:  A timeout occurred
    - UNEX: Unexpected SCCB completion

  * Other (not traced at default level):
    - SYN1: Synchronous wait start
    - SYN2: Synchronous wait end

Since the SCLP interface is used by console drivers this patch also
moves s390dbf printks outside the critical section protected by debug
area locks to prevent a potential deadlock that would otherwise be
introduced between console_owner --> sclp_lock --> sclp_debug.lock.

Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Debug areas can currently only be used after s390dbf initialization
which occurs as a postcore_initcall. This is too late for tracing
earlier code such as that related to console_init().

This patch introduces a macro for defining a statically initialized
debug area that can be used to trace very early code. The macro is made
available for built-in code only because modules are never running
during early boot.

Example usage:

1. Define static debug area:

  DEFINE_STATIC_DEBUG_INFO(my_debug, "my_debug", 4, 1, 16,
			   &debug_hex_ascii_view);

2. Add trace entry:

  debug_event(&my_debug, 0, "DATA", 4);

Note: The debug area is automatically registered in debugfs during boot.
      A driver must not call any of the debug_register()/_unregister()
      functions on a static debug_info_t!

Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Currently allocation and registration of s390dbf debug areas are tied
together. As a result, a debug area cannot be unregistered and
re-registered while any process has an associated debugfs file open.

Fix this by splitting alloc/release from register/unregister.

Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Any previously recorded s390dbf debug data is reset when a debug area
is resized using the 'pages' sysfs attribute. This can make
live-debugging unnecessarily complex.

Fix this by copying existing debug data to the newly allocated debug
area when resizing.

Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

When read via debugfs, s390dbf debug-views print the kernel address of
the call-site that created a trace entry. The kernel's %p pointer
hashing feature obfuscates this address, and commit 860ec7c6e21c
("s390/debug: use pK for kernel pointers") made this obfuscation
configurable via the kptr_restrict sysctl.

Obfuscation of kernel address data printed via s390dbf debug-views does
not add any additional protection since the associated debugfs files are
only accessible to the root user that typically has enough other means
to obtain kernel address data.

Also trace payload data may contain binary representations of kernel
addresses as part of logged data structues. Requiring such payload data
to be obfuscated as well would be impractical and greatly diminish the
use of s390dbf.

Therefore completely remove pointer obfuscation from s390dbf
debug-views.

Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

Change __debug_entry structure in the following way:
 - remove redundant union
 - Field containing cpuid is expanded to 16 bits. 8-bit width was not
   enough since we already support up to 512 cpus.
 - Field containing the timestamp is expanded to 60 bits. The timestamp
   itself is now stored in the absolute Unix time format in microseconds
   taking the Epoch Index into acount.
Adjust default header for debug entries by setting minimum width for cpuid
to 4 digits.

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

There is not a single user of the debug raw view. Therefore remove it
before anybody uses it. If anybody would make use of the view it would
expose the struct __debug_entry definition to userspace and really
would make it uapi. This wouldn't be good, since the definition is
suboptimal and needs to be changed.

Right now the structure definition is only defined to be uapi, however
there is no user.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

When specifying insanely large debug buffers a kernel warning is
printed. The debug code does handle the error gracefully, though.
Instead of duplicating the check let us silence the warning to
avoid crashes when panic_on_warn is used.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>

Instead of having all the sysctl handlers deal with user pointers, which
is rather hairy in terms of the BPF interaction, copy the input to and
from  userspace in common code.  This also means that the strings are
always NUL-terminated by the common code, making the API a little bit
safer.

As most handler just pass through the data to one of the common handlers
a lot of the changes are mechnical.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>