ZTS: Use correct signal numbers for status checks

Different operating systems encode exit status in different ways.
The logapi shell library assumes the Solaris meaning of exit codes,
which is not correct on other platforms.

Define the needed constants according to the platform we are running
on and use those to decode process exit status.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes openzfs#10121

tests/test-runner/include/logapi.shlib

@@ -165,6 +165,29 @@ function log_mustnot_expect
 	(( $? != 0 )) && log_fail
 }
 
+# Exit status encoding is platform-dependent
+case $(uname) in
+Darwin|FreeBSD)
+	EXIT_SIGNAL=128
+	SIGBUS=10
+	SIGSEGV=11
+	;;
+illumos)
+	EXIT_SIGNAL=256
+	SIGBUS=7
+	SIGSEGV=11
+	;;
+Linux|*)
+	EXIT_SIGNAL=128
+	SIGBUS=7
+	SIGSEGV=11
+	;;
+esac
+EXIT_SUCCESS=0
+EXIT_NOTFOUND=127
+EXIT_SIGBUS=$((EXIT_SIGNAL + SIGBUS))
+EXIT_SIGSEGV=$((EXIT_SIGNAL + SIGSEGV))
+
 # Execute and print command with status where success equals non-zero result
 # or output includes expected keyword
 #
@@ -191,19 +214,19 @@ function log_neg_expect
 	out="cat $logfile"
 
 	# unexpected status
-	if (( $status == 0 )); then
+	if (( $status == EXIT_SUCCESS )); then
 		 print -u2 $($out)
 		_printerror "$@" "unexpectedly exited $status"
 	# missing binary
-	elif (( $status == 127 )); then
+	elif (( $status == EXIT_NOTFOUND )); then
 		print -u2 $($out)
 		_printerror "$@" "unexpectedly exited $status (File not found)"
-	# bus error - core dump (256+signal, SIGBUS=7)
-	elif (( $status == 263 )); then
+	# bus error - core dump
+	elif (( $status == EXIT_SIGBUS )); then
 		print -u2 $($out)
 		_printerror "$@" "unexpectedly exited $status (Bus Error)"
-	# segmentation violation - core dump (256+signal, SIGSEGV=11)
-	elif (( $status == 267 )); then
+	# segmentation violation - core dump
+	elif (( $status == EXIT_SIGSEGV )); then
 		print -u2 $($out)
 		_printerror "$@" "unexpectedly exited $status (SEGV)"
 	else