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Opotimize "scno >= 0 && scno < nsyscalls" check

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gcc can't figure out on its own that this check can be done with
single compare, and does two compares. We can help it by casting
scno to unsigned long: ((unsigned long)(scno) < nsyscalls)

* defs.h: New macro SCNO_IN_RANGE(long_var).
* count.c (count_syscall): Use SCNO_IN_RANGE() instead of open-coded check.
* syscall.c (getrval2): Use SCNO_IN_RANGE() instead of open-coded check.
This fixes a bug: missing check for scno < 0 and scno > nsyscalls
instead of scno >= nsyscalls.
(get_scno): Use SCNO_IN_RANGE() instead of open-coded check.
This fixes a bug: scno > nsyscalls instead of scno >= nsyscalls.
(known_scno): Use SCNO_IN_RANGE() instead of open-coded check.
(internal_syscall): Likewise.
(syscall_enter): Likewise.
(trace_syscall_entering): Likewise.
(get_error): Likewise.
(trace_syscall_exiting): Likewise.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko 2011-08-25 01:13:43 +02:00
parent 1a5b5a7aff
commit cb6f056004
3 changed files with 27 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
count.c
View File

@ -50,7 +50,7 @@ static struct timeval shortest = { 1000000, 0 };
void
count_syscall(struct tcb *tcp, struct timeval *tv)
{
if (tcp->scno < 0 || tcp->scno >= nsyscalls)
if (!SCNO_IN_RANGE(tcp->scno))
return;
if (!counts) {

2
defs.h
View File

@ -728,6 +728,8 @@ extern unsigned nioctlents;
extern const char *const *signalent;
extern unsigned nsignals;
#define SCNO_IN_RANGE(scno) ((unsigned long)(scno) < nsyscalls)
#if HAVE_LONG_LONG
/* _l refers to the lower numbered u_arg,

47
syscall.c
View File

@ -675,11 +675,12 @@ getrval2(struct tcb *tcp)
int
sys_indir(struct tcb *tcp)
{
int i, scno, nargs;
int i, nargs;
long scno;
if (entering(tcp)) {
scno = tcp->u_arg[0];
if (scno > nsyscalls) {
if (!SCNO_IN_RANGE(scno)) {
fprintf(stderr, "Bogus syscall: %u\n", scno);
return 0;
}
@ -1045,7 +1046,7 @@ get_scno(struct tcb *tcp)
r2 = regs[REG_V0];
scno = r2;
if (scno < 0 || scno > nsyscalls) {
if (!SCNO_IN_RANGE(scno)) {
if (a3 == 0 || a3 == -1) {
if (debug)
fprintf(stderr, "stray syscall exit: v0 = %ld\n", scno);
@ -1058,7 +1059,7 @@ get_scno(struct tcb *tcp)
if (upeek(tcp, REG_V0, &scno) < 0)
return -1;
if (scno < 0 || scno > nsyscalls) {
if (!SCNO_IN_RANGE(scno)) {
if (a3 == 0 || a3 == -1) {
if (debug)
fprintf(stderr, "stray syscall exit: v0 = %ld\n", scno);
@ -1075,7 +1076,7 @@ get_scno(struct tcb *tcp)
* Do some sanity checks to figure out if it's
* really a syscall entry
*/
if (scno < 0 || scno > nsyscalls) {
if (!SCNO_IN_RANGE(scno)) {
if (a3 == 0 || a3 == -1) {
if (debug)
fprintf(stderr, "stray syscall exit: r0 = %ld\n", scno);
@ -1228,7 +1229,7 @@ known_scno(struct tcb *tcp)
{
long scno = tcp->scno;
#if SUPPORTED_PERSONALITIES > 1
if (scno >= 0 && scno < nsyscalls && sysent[scno].native_scno != 0)
if (SCNO_IN_RANGE(scno) && sysent[scno].native_scno != 0)
scno = sysent[scno].native_scno;
else
#endif
@ -1425,7 +1426,7 @@ internal_syscall(struct tcb *tcp)
*/
int (*func)();
if (tcp->scno < 0 || tcp->scno >= nsyscalls)
if (!SCNO_IN_RANGE(tcp->scno))
return 0;
func = sysent[tcp->scno].sys_func;
@ -1464,7 +1465,7 @@ syscall_enter(struct tcb *tcp)
#ifdef LINUX
int i, nargs;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
if (SCNO_IN_RANGE(tcp->scno))
nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
nargs = tcp->u_nargs = MAX_ARGS;
@ -1635,7 +1636,7 @@ syscall_enter(struct tcb *tcp)
#endif /* LINUX */
#ifdef SUNOS4
int i, nargs;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
if (SCNO_IN_RANGE(tcp->scno))
nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
else
nargs = tcp->u_nargs = MAX_ARGS;
@ -1653,7 +1654,7 @@ syscall_enter(struct tcb *tcp)
* SGI is broken: even though it has pr_sysarg, it doesn't
* set them on system call entry. Get a clue.
*/
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
if (SCNO_IN_RANGE(tcp->scno))
tcp->u_nargs = sysent[tcp->scno].nargs;
else
tcp->u_nargs = tcp->status.pr_nsysarg;
@ -1671,7 +1672,7 @@ syscall_enter(struct tcb *tcp)
/*
* Like SGI, UnixWare doesn't set pr_sysarg until system call exit
*/
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
if (SCNO_IN_RANGE(tcp->scno))
tcp->u_nargs = sysent[tcp->scno].nargs;
else
tcp->u_nargs = tcp->status.pr_lwp.pr_nsysarg;
@ -1679,14 +1680,14 @@ syscall_enter(struct tcb *tcp)
tcp->u_nargs * sizeof(tcp->u_arg[0]), (char *) tcp->u_arg);
# elif defined(HAVE_PR_SYSCALL)
int i;
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
if (SCNO_IN_RANGE(tcp->scno))
tcp->u_nargs = sysent[tcp->scno].nargs;
else
tcp->u_nargs = tcp->status.pr_nsysarg;
for (i = 0; i < tcp->u_nargs; i++)
tcp->u_arg[i] = tcp->status.pr_sysarg[i];
# elif defined(I386)
if (tcp->scno >= 0 && tcp->scno < nsyscalls)
if (SCNO_IN_RANGE(tcp->scno))
tcp->u_nargs = sysent[tcp->scno].nargs;
else
tcp->u_nargs = 5;
@ -1698,7 +1699,7 @@ syscall_enter(struct tcb *tcp)
# endif
#endif /* SVR4 */
#ifdef FREEBSD
if (tcp->scno >= 0 && tcp->scno < nsyscalls &&
if (SCNO_IN_RANGE(tcp->scno) &&
sysent[tcp->scno].nargs > tcp->status.val)
tcp->u_nargs = sysent[tcp->scno].nargs;
else
@ -1756,7 +1757,7 @@ trace_syscall_entering(struct tcb *tcp)
tcp_last = tcp;
if (scno_good != 1)
tprintf("????" /* anti-trigraph gap */ "(");
else if (tcp->scno >= nsyscalls || tcp->scno < 0)
else if (!SCNO_IN_RANGE(tcp->scno))
tprintf("syscall_%lu(", tcp->scno);
else
tprintf("%s(", sysent[tcp->scno].sys_name);
@ -1857,7 +1858,7 @@ trace_syscall_entering(struct tcb *tcp)
internal_syscall(tcp);
if ((tcp->scno >= 0 && tcp->scno < nsyscalls &&
if ((SCNO_IN_RANGE(tcp->scno) &&
!(qual_flags[tcp->scno] & QUAL_TRACE)) ||
(tracing_paths && !pathtrace_match(tcp))) {
tcp->flags |= TCB_INSYSCALL | TCB_FILTERED;
@ -1874,11 +1875,11 @@ trace_syscall_entering(struct tcb *tcp)
printleader(tcp);
tcp->flags &= ~TCB_REPRINT;
tcp_last = tcp;
if (tcp->scno >= nsyscalls || tcp->scno < 0)
if (!SCNO_IN_RANGE(tcp->scno))
tprintf("syscall_%lu(", tcp->scno);
else
tprintf("%s(", sysent[tcp->scno].sys_name);
if (tcp->scno >= nsyscalls || tcp->scno < 0 ||
if (!SCNO_IN_RANGE(tcp->scno) ||
((qual_flags[tcp->scno] & QUAL_RAW) &&
sysent[tcp->scno].sys_func != sys_exit))
res = printargs(tcp);
@ -2011,7 +2012,7 @@ get_error(struct tcb *tcp)
int u_error = 0;
#ifdef LINUX
int check_errno = 1;
if (tcp->scno >= 0 && tcp->scno < nsyscalls &&
if (SCNO_IN_RANGE(tcp->scno) &&
sysent[tcp->scno].sys_flags & SYSCALL_NEVER_FAILS) {
check_errno = 0;
}
@ -2257,7 +2258,7 @@ dumpio(struct tcb *tcp)
return;
if (tcp->u_arg[0] < 0 || tcp->u_arg[0] >= MAX_QUALS)
return;
if (tcp->scno < 0 || tcp->scno >= nsyscalls)
if (!SCNO_IN_RANGE(tcp->scno))
return;
if (sysent[tcp->scno].sys_func == printargs)
return;
@ -2317,7 +2318,7 @@ trace_syscall_exiting(struct tcb *tcp)
if (tcp->flags & TCB_REPRINT) {
printleader(tcp);
if (tcp->scno >= nsyscalls || tcp->scno < 0)
if (!SCNO_IN_RANGE(tcp->scno))
tprintf("<... syscall_%lu resumed> ", tcp->scno);
else
tprintf("<... %s resumed> ", sysent[tcp->scno].sys_name);
@ -2340,7 +2341,7 @@ trace_syscall_exiting(struct tcb *tcp)
return res;
}
if (tcp->scno >= nsyscalls || tcp->scno < 0
if (!SCNO_IN_RANGE(tcp->scno)
|| (qual_flags[tcp->scno] & QUAL_RAW))
sys_res = printargs(tcp);
else {
@ -2360,7 +2361,7 @@ trace_syscall_exiting(struct tcb *tcp)
tprintf(") ");
tabto(acolumn);
u_error = tcp->u_error;
if (tcp->scno >= nsyscalls || tcp->scno < 0 ||
if (!SCNO_IN_RANGE(tcp->scno) ||
qual_flags[tcp->scno] & QUAL_RAW) {
if (u_error)
tprintf("= -1 (errno %ld)", u_error);