tests/kernel/h_segv: Disable SIGFPE test on RISC-V.

No floating-point exception traps on RISC-V.

Also don't pass the result of divide-by-zero converted to integer to
usleep. Although the floating-point result of divide-by-zero is
well-defined by IEEE 754 (+/-infinity), the outcome of C conversion
to integer is not. And while on some architectures this might return
zero, on RISC-V it looks like it'll return all bits set. And as of
PR 58184, usleep now honours sleeps longer than 1sec, which means
this will be waiting at least two billion microseconds, or about half
an hour...

So instead, just write the result to a volatile variable.

Fix typo

Clean up terminology: modern arm CPUs do properly implement IEEE 754
floating point exceptions - but some (actually all currently know ones)
do not implement sending traps when these exceptions are raised.

Pointed out by Peter Maydell.

vaxinate against ieeefp.h

Some arm CPUs do not implement traps on floating point exceptions.

Make fenv.h optional for this test to unbreak the vax build.

Use feenableexcept to trap fp exceptions, and trigger one, for SIGFPE.

Not every CPU traps integer division by zero -- aarch64, powerpc,
&c., just return zero.

Sort #includes.

branches: 1.7.2;
Add a comment for the workaround in trigger_bus()

Explain PROT_READ|PROT_WRITE.

Make the trigger_bus() test compatible with more CPUs (at least ALPHA)

If we write a byte character into a pointer, a compiler can emit a
read-modify-write operation, especially when a CPU cannot access directly
a character wide address.

In this scenario calling mmap(2) with PROT_WRITE, without PROT_READ will
emit unexpected trap.

There are two possible workarounds for this issue:
- write register wide memory without rmw sequence,
- mark the region with additional protection PROT_READ

Both work for NetBSD/alpha.

Go for the latter as perhaps more safe for dump compilers emitting rmw
sequences.

Investigated by <martin>

Handle FPE and BUS scenarios in the ATF t_trapsignal tests

These crash signals are crucial for proper handling of abnormal conditions
in a program. The additional purpose of these tests it to assure the proper
handling of these signals for the coming ptrace(2)-related changes in the
signal routing code.

Add a stub for ILL scenarios.

All tests pass (on amd64).

The shell ATF script contains duplicated code. There should be a way to
deduplicate it, without rewrite to C.

Sponsored by <The NetBSD Foundation>

Extend ATF tests in t_trapsignal.sh to verify software breakpoint traps

There are at least four types of SIGTRAP events:
- software/hardware single step (trace trap)
- software breakpoint
- hardware breakpoint/watchpoint
- kernel event (exec, fork, vfork, vfork-done, lwp-create, lwp-exit)

A program can execute software breakpoint without the context of being
traced and this is a regular crash signal emitting SIGTRAP (TRAP_BRKPT).

Rename original trap_* tests (trap_simple, trap_handle, trap_mask,
trap_handle_recurse and trap_ignore) to segv_* tests and restrict them for
SIGSEGV.

Add new tests: trap_* testing the same scenarios as segv_ ones, however
verifying the software breakpoint trap (SIGTRAP).

Keep the original name of h_segv.c, and extend it for software breakpoint
events.

The purpose of these tests is to verify SIGTRAP kernel paths without the
ptrace(2) context.

All tests pass.

Sponsored by <The NetBSD Foundation>

Add new ATF test: t_trapsignal:trap_ignore

Test ignored trap with right exit code.

This test passes.

Sponsored by <The NetBSD Foundation>

branches: 1.2.2;
fix usage.

Add trapsignal tests that make sure that traps don't end up spinning
indefinitely, discussed in tech-kern.

Fix typo

Clean up terminology: modern arm CPUs do properly implement IEEE 754
floating point exceptions - but some (actually all currently know ones)
do not implement sending traps when these exceptions are raised.

Pointed out by Peter Maydell.

vaxinate against ieeefp.h

Some arm CPUs do not implement traps on floating point exceptions.

Make fenv.h optional for this test to unbreak the vax build.

Use feenableexcept to trap fp exceptions, and trigger one, for SIGFPE.

Not every CPU traps integer division by zero -- aarch64, powerpc,
&c., just return zero.

Sort #includes.

Add a comment for the workaround in trigger_bus()

Explain PROT_READ|PROT_WRITE.

Make the trigger_bus() test compatible with more CPUs (at least ALPHA)

If we write a byte character into a pointer, a compiler can emit a
read-modify-write operation, especially when a CPU cannot access directly
a character wide address.

In this scenario calling mmap(2) with PROT_WRITE, without PROT_READ will
emit unexpected trap.

There are two possible workarounds for this issue:
- write register wide memory without rmw sequence,
- mark the region with additional protection PROT_READ

Both work for NetBSD/alpha.

Go for the latter as perhaps more safe for dump compilers emitting rmw
sequences.

Investigated by <martin>

Handle FPE and BUS scenarios in the ATF t_trapsignal tests

These crash signals are crucial for proper handling of abnormal conditions
in a program. The additional purpose of these tests it to assure the proper
handling of these signals for the coming ptrace(2)-related changes in the
signal routing code.

Add a stub for ILL scenarios.

All tests pass (on amd64).

The shell ATF script contains duplicated code. There should be a way to
deduplicate it, without rewrite to C.

Sponsored by <The NetBSD Foundation>

Extend ATF tests in t_trapsignal.sh to verify software breakpoint traps

There are at least four types of SIGTRAP events:
- software/hardware single step (trace trap)
- software breakpoint
- hardware breakpoint/watchpoint
- kernel event (exec, fork, vfork, vfork-done, lwp-create, lwp-exit)

A program can execute software breakpoint without the context of being
traced and this is a regular crash signal emitting SIGTRAP (TRAP_BRKPT).

Rename original trap_* tests (trap_simple, trap_handle, trap_mask,
trap_handle_recurse and trap_ignore) to segv_* tests and restrict them for
SIGSEGV.

Add new tests: trap_* testing the same scenarios as segv_ ones, however
verifying the software breakpoint trap (SIGTRAP).

Keep the original name of h_segv.c, and extend it for software breakpoint
events.

The purpose of these tests is to verify SIGTRAP kernel paths without the
ptrace(2) context.

All tests pass.

Sponsored by <The NetBSD Foundation>

Add new ATF test: t_trapsignal:trap_ignore

Test ignored trap with right exit code.

This test passes.

Sponsored by <The NetBSD Foundation>

branches: 1.2.2;
fix usage.

Add trapsignal tests that make sure that traps don't end up spinning
indefinitely, discussed in tech-kern.

fix usage.

Add trapsignal tests that make sure that traps don't end up spinning
indefinitely, discussed in tech-kern.