arch, sched/signal: Fix compilation with ENABLE_PARTIAL_SIGNALS=y

[jlaitine]

Summary

Correct build errors when CONFIG_ENABLE_ALL_SIGNALS is not defined

The current master doesn't compile for CONFIG_BUILD_PROTECTED with the following setup:

#
# Signal Configuration
#
# CONFIG_ENABLE_ALL_SIGNALS is not set
CONFIG_ENABLE_PARTIAL_SIGNALS=y
# CONFIG_DISABLE_ALL_SIGNALS is not set

The first errors occur from the svcall:

In file included from armv7-m/arm_svcall.c:32:
armv7-m/arm_svcall.c: In function 'arm_svcall':
armv7-m/arm_svcall.c:250:32: error: 'struct xcptcontext' has no member named 'sigreturn'
  250 |           DEBUGASSERT(rtcb->xcp.sigreturn == 0);
      |                                ^
armv7-m/arm_svcall.c:251:20: error: 'struct xcptcontext' has no member named 'sigreturn'
  251 |           rtcb->xcp.sigreturn  = regs[REG_PC];
      |                    ^
armv7-m/arm_svcall.c:257:53: error: 'struct userspace_s' has no member named 'signal_handler'
  257 |           regs[REG_PC]         = (uint32_t)USERSPACE->signal_handler & ~1;
      |                                                     ^~
armv7-m/arm_svcall.c:292:32: error: 'struct xcptcontext' has no member named 'sigreturn'
  292 |           DEBUGASSERT(rtcb->xcp.sigreturn != 0);
      |                                ^
armv7-m/arm_svcall.c:294:43: error: 'struct xcptcontext' has no member named 'sigreturn'
  294 |           regs[REG_PC]         = rtcb->xcp.sigreturn & ~1;
      |                                           ^
armv7-m/arm_svcall.c:300:20: error: 'struct xcptcontext' has no member named 'sigreturn'
  300 |           rtcb->xcp.sigreturn  = 0;
      |                    ^
make[1]: *** [Makefile:179: arm_svcall.o] Error 1

Fixing that, leads to linker errors with undefined symbols with "nxsig_unmask_pendingsignal" etc.

There are reasons why it compiles for CONFIG_BUILD_FLAT (partially by luck, perhaps partially by design):

• Some of the offending code is behind CONFIG_LIB_SYSCALL, which is defined only in memory protected builds
• Some of the offending code is behind CONFIG_BUILD_PROTECTED in signal handler
• When the nuttx is compiled first into archives and later linked together, the call to nxsig_unmask_pendingsignal is only pulled in in case user calls ppoll, pselect, sigsuspend or such from the code (signal.o is not used in linking)

The two commits in this PR fix the compilation, and also correct the functionality in CONFIG_ENABLE_PARTIAL_SIGNALS. With that flag, signal actions are now disabled, but simple signal delivery and wakeup works.

Impact

No impact on any of the current boards; the ENABLE_FULL_SIGNALS is enabled on !DEFAULT_SMALL, and for all the DEFAULT_SMALL boards currently in mainline, the full signals are enabled explicitly in defconfig.

Testing

Tested the compilation and partial signals using a custom application, with the partial signal configuration, with protected and flat builds. With the fixes, the code builds and runs properly. Without the fix, the build and link errors mentioned in the description, occur on protected build.

The ENABLE_FULL_SIGNALS, ENABLE_PARTIAL_SIGNALS and DISABLE_ALL_SIGNALS configurations have been tested on ostest on qemu-armv8a, together with PR apache/nuttx-apps#3538. The logs are in that PR.

Here is an ostest logfile from stm32f7 real hw, using ENABLE_PARTIAL_SIGNALS
ostest_pixhawk4_partial_signals.txt

[jlaitine]

@xiaoxiang781216 : I believe all the options are now properly working (ENABLE_ALL_SIGNALS, ENABLE_PARTIAL_SIGNALS and DISABLE_ALL_SIGNALS). I have been running these on qemu and stm32f7 real hw. The signal wakeup path didn't work with PARTIAL_SIGNALS at all, also there were build errors in DISABLE_ALL_SIGNALS. So hopefully it is more proper now... All signal actions (signal handlers) have been disabled in CONFIG_ENABLE_PARTIAL_SIGNALS, but basic signal delivery & wakeup works.

I also made a PR in apps/ostest, so that it is actually possible to test these different signal configurations.

[jlaitine]

There was incomplete flagging for CONFIG_DISABLE_ALL_SIGNALS in the button driver, added that into this same PR. I also disabled the signals support from the one FOC board, where flash was overflowing. The signals are not used in foc demo, it only reads (samples) the buttons, so this is fine. And the signals didn't work in CONFIG_ENABLE_PARTIAL_SIGNALS (default for CONFIG_DEFAULT_SMALL) anyways before this commit, so nothing actually changed.

[xiaoxiang781216]

@jlaitine please squash the last three patches into one, and remove the check of CONFIG_DISABLE_ALL_SIGNALS from nuttx/libs/libc/pthread/pthread_mutex_destroy.c

[jlaitine]

@xiaoxiang781216 : I addressed your review requests, thank you for thorough reviews. Current version is now re-tested with qemu armv8 in all signal configuration modes, and the original compilation issues are fixed in protected mode as well.