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By adding tcp->s_ent pointer tot syscall table entry, we can replace sysent[tcp->scno] references by tcp->s_ent. More importantly, we may ensure that tcp->s_ent is always valid, regardless of tcp->scno value. This allows us to drop SCNO_IS_VALID(tcp->scno) checks before we access syscall table entry. We can optimize (qual_flags[tcp->scno] & QUAL_foo) checks with a similar technique. Resulting code shrink: text data bss dec hex filename 245975 700 19072 265747 40e13 strace.t3/strace 245703 700 19072 265475 40d03 strace.t4/strace * count.c (count_syscall): Use cheaper SCNO_IN_RANGE() check. * defs.h: Add "int qual_flg" and "const struct sysent *s_ent" to struct tcb. Remove "int u_nargs" from it. Add UNDEFINED_SCNO constant which will mark undefined scnos in tcp->qual_flg. * pathtrace.c (pathtrace_match): Drop SCNO_IS_VALID check. Use tcp->s_ent instead of sysent[tcp->scno]. * process.c (sys_prctl): Use tcp->s_ent->nargs instead of tcp->u_nargs. (sys_waitid): Likewise. * strace.c (init): Add compile-time check that DEFAULT_QUAL_FLAGS constant is consistent with init code. * syscall.c (decode_socket_subcall): Use tcp->s_ent->nargs instead of tcp->u_nargs. Set tcp->qual_flg and tcp->s_ent. (decode_ipc_subcall): Likewise. (printargs): Use tcp->s_ent->nargs instead of tcp->u_nargs. (printargs_lu): Likewise. (printargs_ld): Likewise. (get_scno): [MIPS,ALPHA] Use cheaper SCNO_IN_RANGE() check. If !SCNO_IS_VALID, set tcp->s_ent and tcp->qual_flg to default values. (internal_fork): Use tcp->s_ent instead of sysent[tcp->scno]. (syscall_fixup_for_fork_exec): Remove SCNO_IS_VALID check. Use tcp->s_ent instead of sysent[tcp->scno]. (get_syscall_args): Likewise. (get_error): Drop SCNO_IS_VALID check where it is redundant. (dumpio): Drop SCNO_IS_VALID check where it is redundant. Use tcp->s_ent instead of sysent[tcp->scno]. (trace_syscall_entering): Use (tcp->qual_flg & UNDEFINED_SCNO) instead of SCNO_IS_VALID check. Use tcp->s_ent instead of sysent[tcp->scno]. Drop SCNO_IS_VALID check where it is redundant. Print undefined syscall name with undefined_scno_name(tcp). (trace_syscall_exiting): Likewise. * util.c (setbpt): Use tcp->s_ent instead of sysent[tcp->scno]. Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This is strace, a system call tracer for Linux. strace is released under a Berkeley-style license at the request of Paul Kranenburg; see the file COPYRIGHT for details. See the file CREDITS for a list of authors and other contributors. See the file INSTALL for compilation and installation instructions. See the file NEWS for information on what has changed in recent versions. You can get the latest version of strace from its homepage at http://sourceforge.net/projects/strace/ . Please send bug reports and enhancements to the strace mailinglist at strace-devel@lists.sourceforge.net.