Build Configuration

In the file le_build_conifg.h are a number of preprocessor macros. Uncommenting these macros enables a non-standard feature of the framework.

LE_MEM_TRACE

When LE_MEM_TRACE is defined, the memory subsystem will create a trace point for every memory pool created. The name of the tracepoint will be the same of the pool, and is of the form "component.poolName".

LE_MEM_VALGRIND

When LE_MEM_VALGRIND is enabled the memory system doesn't use pools anymore but in fact switches to use malloc/free per-block. This way, tools like valgrind can be used on a Legato executable.

LE_SMACK_DISABLE

Legato provides the ability to disable the SMACK API. We don’t recommend disabling SMACK: users do so at their own risk.

By disabling SMACK, you essentially render the SMACK APIs to do nothing; SMACK labels aren’t set during Legato runtime. On the Yocto side, disabling SMACK will not apply SMACK labels on certain processes, files, and directories.

If Legato's SMACK API is disabled, users must set SMACK labels for their own runtime environment if they want to use SMACK security.

To disable SMACK, follow these steps:

  • Edit "framework/include/le_build_config.h" and uncomment "//#define LE_SMACK_DISABLE".
  • Build Legato.
  • Flash the resulting legato.cwe or legatoz.cwe with the fwupdate tool. Do not install Legato with "instlegato".
  • After the target reboots, it should have the file "/legato/SMACK_DISABLED".
  • Reboot the target again.

To re-enable SMACK, follow these steps:

  • Edit "framework/include/le_build_config.h" and comment "#define LE_SMACK_DISABLE".
  • Build Legato.
  • Flash the resulting legato.cwe or legatoz.cwe with the fwupdate tool. Do not install Legato with "instlegato".
  • After the target reboots, it should not have the file "/legato/SMACK_DISABLED".
  • Reboot the target again.

LE_SEGV_HANDLER_DISABLE

When LE_SEGV_HANDLER_DISABLE is disabled, the ShowStackSignalHandler() will not use signal derivation and sigsetjmp()/siglongjmp() to continue and try to survive to invalid memory access while decoding the stack or the back-trace. This "2nd-level" handler is an ultimate protection against SEGV. However this handler relies on undefined behaviour of sigsetjmp(), so is more risky.

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