syscalls: use gperf for lookup

use gperf to generate a perfect hash to lookup syscall names.   It
improves significantly the complexity for seccomp_syscall_resolve_name.*
since it replaces the expensive strcmp for each syscall in the
database, with a lookup table.

The complexity for syscall_resolve_num is not changed and it
uses the linear search, that is anyway less expensive than
seccomp_syscall_resolve_name.* as it uses an index for comparison
instead of doing a string comparison.

On my machine, calling 1000 seccomp_syscall_resolve_name_arch and
seccomp_syscall_resolve_num_arch over the entire syscalls DB passed
from ~0.45 sec to ~0.06s.

Closes: seccomp#207

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

.travis.yml

@@ -32,6 +32,7 @@ addons:
       - valgrind
       - clang
       - lcov
+      - gperf
 
 env:
   global:

configure.ac

@@ -119,6 +119,11 @@ AC_DEFINE_UNQUOTED([ENABLE_PYTHON],
 	[$(test "$enable_python" = yes && echo 1 || echo 0)],
 	[Python bindings build flag.])
 
+AC_CHECK_TOOL(GPERF, gperf)
+if test -z "$GPERF"; then
+	AC_MSG_ERROR(please install gperf)
+fi
+
 dnl ####
 dnl coverity checks
 dnl ####

src/Makefile.am

@@ -31,20 +31,21 @@ SOURCES_ALL = \
 	hash.h hash.c \
 	db.h db.c \
 	arch.c arch.h \
-	arch-x86.h arch-x86.c arch-x86-syscalls.c \
-	arch-x86_64.h arch-x86_64.c arch-x86_64-syscalls.c \
-	arch-x32.h arch-x32.c arch-x32-syscalls.c \
-	arch-arm.h arch-arm.c arch-arm-syscalls.c \
-	arch-aarch64.h arch-aarch64.c arch-aarch64-syscalls.c \
-	arch-mips.h arch-mips.c arch-mips-syscalls.c \
-	arch-mips64.h arch-mips64.c arch-mips64-syscalls.c \
-	arch-mips64n32.h arch-mips64n32.c arch-mips64n32-syscalls.c \
-	arch-parisc.h arch-parisc.c arch-parisc64.c arch-parisc-syscalls.c \
-	arch-ppc.h arch-ppc.c arch-ppc-syscalls.c \
-	arch-ppc64.h arch-ppc64.c arch-ppc64-syscalls.c \
-	arch-riscv64.h arch-riscv64.c arch-riscv64-syscalls.c \
-	arch-s390.h arch-s390.c arch-s390-syscalls.c \
-	arch-s390x.h arch-s390x.c arch-s390x-syscalls.c
+	arch-x86.h arch-x86.c \
+	arch-x86_64.h arch-x86_64.c \
+	arch-x32.h arch-x32.c \
+	arch-arm.h arch-arm.c \
+	arch-aarch64.h arch-aarch64.c \
+	arch-mips.h arch-mips.c \
+	arch-mips64.h arch-mips64.c \
+	arch-mips64n32.h arch-mips64n32.c \
+	arch-parisc.h arch-parisc.c arch-parisc64.c \
+	arch-ppc.h arch-ppc.c \
+	arch-ppc64.h arch-ppc64.c \
+	arch-riscv64.h arch-riscv64.c \
+	arch-s390.h arch-s390.c \
+	arch-s390x.h arch-s390x.c\
+	syscalls.c syscalls.perf.c
 
 EXTRA_DIST = arch-syscall-validate
 
@@ -68,5 +69,14 @@ libseccomp_la_CFLAGS = ${AM_CFLAGS} ${CODE_COVERAGE_CFLAGS} ${CFLAGS} \
 libseccomp_la_LDFLAGS = ${AM_LDFLAGS} ${CODE_COVERAGE_LDFLAGS} ${LDFLAGS} \
 	-version-number ${VERSION_MAJOR}:${VERSION_MINOR}:${VERSION_MICRO}
 
+EXTRA_DIST += syscalls.perf.c syscalls.perf
+CLEANFILES = syscalls.perf.c syscalls.perf
+
+syscalls.perf: syscalls.csv syscalls.perf.template
+	${AM_V_GEN} ./generate_syscalls_perf.sh
+
+syscalls.perf.c: syscalls.perf
+	${GPERF} -m 100 --null-strings --pic -tCEG -T -S1 $< > $@
+
 check-build:
 	${MAKE} ${AM_MAKEFLAGS} ${check_PROGRAMS}