[GitHub] [nuttx] yamt opened a new issue, #10326: signal handler is called within "kernel"

["yamt (via GitHub)" <gi...@apache.org>]

yamt opened a new issue, #10326:
URL: https://github.com/apache/nuttx/issues/10326

   nuttx, at least w/o CONFIG_LIB_SYSCALL, calls user-specified signal hander within the "kernel" part of the code directly.
   it isn't safe because user handler can call system calls.
   
   in the extreme case, the user handler escapes with a `longjmp`. it likely crashes the kernel later.
   unfortunately it's somehow common for apps for posix environment to use longjmp within a signal handler.
   
   while CONFIG_LIB_SYSCALL seems to defer signal delivery as expected (i haven't tested this. just glancing the code)
   it isn't always desirable because:
   * it has considerable overhead like linking otherwise unused system calls
   * you need to write arch-dependent code (eg. sim doesn't have an implementation right now)
   
   i guess a lighter-weight fix is nicer to have. eg. making every syscall-type functions call, say,`enter_kernel`/`leave_kernel`.
   


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