Merge "llkd: add bit_wait_io to stack monitoring" am: 5ff35fbd am: 5d08103e

ABA detection since forward scheduling progress is allowed, thus the condition

for the symbols are:

- Check is looking for " " + __symbol__+ "0x" in /proc/<pid>/stack.

- Check is looking for " __symbol__+0x" or " __symbol__.cfi+0x" in

  /proc/__pid__/stack.

- The __symbol__ should be rare and short lived enough that on a typical

  system the function is seen at most only once in a sample over the timeout

  period of ro.llk.stack.timeout_ms, samples occur every ro.llk.check_ms. This

#### ro.llk.stack.timeout_ms

default ro.llk.timeout_ms,

checking for persistent stack symbols maximum timelimit.

Only active on userdebug and eng builds.

Only active on userdebug or eng builds.

#### ro.llk.check_ms

default 2 minutes samples of threads for D or Z.

#### ro.llk.stack

default cma_alloc,__get_user_pages, comma separated list of kernel symbols.

The string "*false*" is the equivalent to an *empty* list.

default cma_alloc,__get_user_pages,bit_wait_io comma separated list of kernel

symbols.  The string "*false*" is the equivalent to an *empty* list.

Look for kernel stack symbols that if ever persistently present can

indicate a subsystem is locked up.

Beware, check does not on purpose do forward scheduling ABA except by polling

should be exceptionally rare and fleeting.

One must be convinced that it is virtually *impossible* for symbol to show up

persistently in all samples of the stack.

Only active on userdebug and eng builds.

Again, looks for a match for either " **symbol**+0x" or " **symbol**.cfi+0x"

in stack expansion.

Only available on userdebug or eng builds, limited privileges due to security

concerns on user builds prevents this checking.

#### ro.llk.blacklist.process

default 0,1,2 (kernel, init and [kthreadd]) plus process names

init,[kthreadd],[khungtaskd],lmkd,lmkd.llkd,llkd,watchdogd,

init,[kthreadd],[khungtaskd],lmkd,llkd,watchdogd,

[watchdogd],[watchdogd/0],...,[watchdogd/***get_nprocs**-1*].

The string "*false*" is the equivalent to an *empty* list.

Do not watch these processes.  A process can be comm, cmdline or pid reference.

Do not watch processes that match this uid.

#### ro.llk.blacklist.process.stack

default process names init,lmkd,lmkd.llkd,llkd,keystore,logd.

default process names init,lmkd.llkd,llkd,keystore,ueventd,apexd,logd.

The string "*false*" is the equivalent to an *empty* list.

This subset of processes are not monitored for live lock stack signatures.

Also prevents the sepolicy violation associated with processes that block

/* LLK_CHECK_MS_DEFAULT = actual timeout_ms / LLK_CHECKS_PER_TIMEOUT_DEFAULT */

#define LLK_CHECKS_PER_TIMEOUT_DEFAULT 5

#define LLK_CHECK_STACK_PROPERTY       "ro.llk.stack"

#define LLK_CHECK_STACK_DEFAULT        "cma_alloc,__get_user_pages"

#define LLK_CHECK_STACK_DEFAULT        "cma_alloc,__get_user_pages,bit_wait_io"

#define LLK_BLACKLIST_PROCESS_PROPERTY "ro.llk.blacklist.process"

#define LLK_BLACKLIST_PROCESS_DEFAULT  \

    "0,1,2,init,[kthreadd],[khungtaskd],lmkd,llkd,watchdogd,[watchdogd],[watchdogd/0]"

    char match = -1;

    for (const auto& stack : llkCheckStackSymbols) {

        if (++idx < 0) break;

        if (kernel_stack.find(" "s + stack + "+0x") != std::string::npos) {

        if ((kernel_stack.find(" "s + stack + "+0x") != std::string::npos) ||

            (kernel_stack.find(" "s + stack + ".cfi+0x") != std::string::npos)) {

            match = idx;

            break;

        }