fix condition code. x1==0 is parent.

branches: 1.1.4; 1.1.24; 1.1.26;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

Merge all MD __sigaction14_sigtramp.c copies into one:
- sparc and sparc64 were not using version 0 sigcontext when there were
no arguments in the signal version. This was probably a bug.
- vax is using +1 the version numbers of the other archs.
- Only hppa was defining __LIBC12_SOURCE__ so it was getting a working
sigcontext before. all the other ports that supported sigcontext had
the compat code disabled.
[pointed out by thorpej, thanks!]
If we want to remove sigcontext support from userland at least now there
is less work to do so.

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

Because the PC is not a general purpose register on aarch64, we need
to use DWARF pseudo-register for the signal trampoline return address.

Adjust the style to match other platforms.

Update the unwinder comment to better reflect ARM64

s/ARM/ARM64/ in comment

Restore SP from mcontext

Improves unwinding of multiple frames without frame pointer.

Change x30 to lr for ease of reading

NFCI

Decorate the aarch64 signal trampoline with CFI attributes easing unwinding

Now, the unwinders (in backtrace(3) and similar) can unwind properly
the stack from a signal handler.

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

use adrp not adr, since the data is not pc-rel. fixes brk(2).

branches: 1.1.4; 1.1.26;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

return 0xffffffffffffffff (= -1). not 0x00000000ffffffff.

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

Mark exect(3) obsolete and bind it to plain execve(2) on all platforms

The original exect(2) from BSD4.2 was enabling bit for tracing
(single-step mode) and calling execve(2). The purpose of it was to generate
a signal for a tracer once the application will change its image to a new
program.

This approach no longer works as:
- exect(2) traces (single-steps) libc and it requires hundreds or
thousands steps before entering a new image
- it's vax and x86 specific code
- this functionality has been moved to the kernel - once a process is
traced it will generate SIGTRAP with si_code TRAP_EXEC and route it to
its debugger
- the side effects and unportability make this interface unusable
- there are no known users of this interface
- it apparently never worked better since day0 of NetBSD ("day0 bug")

Users are requested to move to other execve(2) variants. Calling current
execve(2) as it is the most similar behavior to this one from BSD4.2.

Discussed several times on mailing lists and in PR/51700.

Add warning to exect(3) telling about marking this function obsolete.

This function is prepared to be removed in next libc major bump.

Sponsored by <The NetBSD Foundation>

branches: 1.1.4; 1.1.8; 1.1.12;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

lower case 'ret' to avoid macro clash

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

fix a bug. no need postincrement here.

branches: 1.1.4; 1.1.24; 1.1.26;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

branches: 1.1.4;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.

Rename "syscall" to "_syscall" and provide "syscall" as a weak alias.

branches: 1.1.4; 1.1.26;
Preliminary files for AARCH64 (64-bit ARM) support.
Enough for a distribution build.