On Tue, Aug 23, 2011 at 12:34:14PM +0200, Denys Vlasenko wrote: > Usage -1 as argument count in syscallent tables > necessitates the check for it, a-la: > > if (tcp->scno >= 0 && tcp->scno < nsyscalls && > sysent[tcp->scno].nargs != -1) > tcp->u_nargs = sysent[tcp->scno].nargs; > else > tcp->u_nargs = MAX_ARGS; > > which is stupid: we waste cycles checking something which > is constant and known at compile time. > > I propose to fix it with these changes: > > * Replace all -1 by MA in all tables. > * Redefine struct sysent::nargs as unsigned > (sadly, this is mostly cosmetic, as gcc won't warn > about -1 static initializer for unsigned field, but still...) > * Add #define MA MAX_ARGS / #undef MA around #include "syscallent[N].h" > * Remove sysent[tcp->scno].nargs != -1 checks. > > This seems a good plan to me, so I'm going to commit these changes,
I agree, but first I'd like to reduce redundancy in syscall_enter().
I have a not quite tested patch, please have a look:
diff --git a/syscall.c b/syscall.c
index 2fd5bb4..7beb0cb 100644
--- a/syscall.c
+++ b/syscall.c
@@ -1949,22 +1949,20 @@ static int
syscall_enter(struct tcb *tcp)
{
#ifdef LINUX
-# if defined(S390) || defined(S390X)
int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
+
+ if (tcp->scno >= 0 && tcp->scno < nsyscalls &&
+ sysent[tcp->scno].nargs >= 0 && sysent[tcp->scno].nargs <= MAX_ARGS)
tcp->u_nargs = sysent[tcp->scno].nargs;
else
tcp->u_nargs = MAX_ARGS;
+
+# if defined(S390) || defined(S390X)
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, i==0 ? PT_ORIGGPR2 : PT_GPR2 + i*sizeof(long),
&tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(ALPHA)
- int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; i++) {
/* WTA: if scno is out-of-bounds this will bomb. Add range-check
* for scno somewhere above here!
@@ -1974,7 +1972,7 @@ syscall_enter(struct tcb *tcp)
}
# elif defined(IA64)
if (!ia32) {
- unsigned long *out0, cfm, sof, sol, i;
+ unsigned long *out0, cfm, sof, sol;
long rbs_end;
/* be backwards compatible with kernel < 2.4.4... */
# ifndef PT_RBS_END
@@ -1990,80 +1988,53 @@ syscall_enter(struct tcb *tcp)
sol = (cfm >> 7) & 0x7f;
out0 = ia64_rse_skip_regs((unsigned long *) rbs_end, -sof +
sol);
- if (tcp->scno >= 0 && tcp->scno < nsyscalls
- && sysent[tcp->scno].nargs != -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; ++i) {
if (umoven(tcp, (unsigned long)
ia64_rse_skip_regs(out0, i),
sizeof(long), (char *) &tcp->u_arg[i]) < 0)
return -1;
}
} else {
- int i;
+ static const int argreg[MAX_ARGS] = { PT_R11 /* EBX = out0 */,
+ PT_R9 /* ECX = out1 */,
+ PT_R10 /* EDX = out2 */,
+ PT_R14 /* ESI = out3 */,
+ PT_R15 /* EDI = out4 */,
+ PT_R13 /* EBP = out5 */ };
- if (/* EBX = out0 */
- upeek(tcp, PT_R11, (long *) &tcp->u_arg[0]) < 0
- /* ECX = out1 */
- || upeek(tcp, PT_R9, (long *) &tcp->u_arg[1]) < 0
- /* EDX = out2 */
- || upeek(tcp, PT_R10, (long *) &tcp->u_arg[2]) < 0
- /* ESI = out3 */
- || upeek(tcp, PT_R14, (long *) &tcp->u_arg[3]) < 0
- /* EDI = out4 */
- || upeek(tcp, PT_R15, (long *) &tcp->u_arg[4]) < 0
- /* EBP = out5 */
- || upeek(tcp, PT_R13, (long *) &tcp->u_arg[5]) < 0)
- return -1;
-
- for (i = 0; i < 6; ++i)
+ for (i = 0; i < tcp->u_nargs; ++i) {
+ if (upeek(tcp, argreg[i], &tcp->u_arg[i]) < 0)
+ return -1;
/* truncate away IVE sign-extension */
tcp->u_arg[i] &= 0xffffffff;
-
- if (tcp->scno >= 0 && tcp->scno < nsyscalls
- && sysent[tcp->scno].nargs != -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = 5;
+ }
}
# elif defined(LINUX_MIPSN32) || defined(LINUX_MIPSN64)
/* N32 and N64 both use up to six registers. */
unsigned long long regs[38];
- int i, nargs;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- nargs = tcp->u_nargs = MAX_ARGS;
if (ptrace(PTRACE_GETREGS, tcp->pid, NULL, (long) ®s) < 0)
return -1;
- for (i = 0; i < nargs; i++) {
+ for (i = 0; i < tcp->u_nargs; i++) {
tcp->u_arg[i] = regs[REG_A0 + i];
# if defined(LINUX_MIPSN32)
tcp->ext_arg[i] = regs[REG_A0 + i];
# endif
}
# elif defined(MIPS)
- long sp;
- int i, nargs;
+ if (tcp->u_nargs > 4) {
+ long sp;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- nargs = tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- nargs = tcp->u_nargs = MAX_ARGS;
- if (nargs > 4) {
if (upeek(tcp, REG_SP, &sp) < 0)
return -1;
for (i = 0; i < 4; i++) {
if (upeek(tcp, REG_A0 + i, &tcp->u_arg[i]) < 0)
return -1;
}
- umoven(tcp, sp+16, (nargs-4) * sizeof(tcp->u_arg[0]),
+ umoven(tcp, sp+16, (tcp->u_nargs - 4) * sizeof(tcp->u_arg[0]),
(char *)(tcp->u_arg + 4));
} else {
- for (i = 0; i < nargs; i++) {
+ for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, REG_A0 + i, &tcp->u_arg[i]) < 0)
return -1;
}
@@ -2072,11 +2043,6 @@ syscall_enter(struct tcb *tcp)
# ifndef PT_ORIG_R3
# define PT_ORIG_R3 34
# endif
- int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, (i==0) ?
(sizeof(unsigned long) * PT_ORIG_R3) :
@@ -2085,33 +2051,17 @@ syscall_enter(struct tcb *tcp)
return -1;
}
# elif defined(SPARC) || defined(SPARC64)
- int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; i++)
tcp->u_arg[i] = regs.u_regs[U_REG_O0 + i];
# elif defined(HPPA)
- int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, PT_GR26-4*i, &tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(ARM)
- int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; i++)
tcp->u_arg[i] = regs.uregs[i];
# elif defined(AVR32)
- tcp->u_nargs = sysent[tcp->scno].nargs;
tcp->u_arg[0] = regs.r12;
tcp->u_arg[1] = regs.r11;
tcp->u_arg[2] = regs.r10;
@@ -2119,25 +2069,17 @@ syscall_enter(struct tcb *tcp)
tcp->u_arg[4] = regs.r5;
tcp->u_arg[5] = regs.r3;
# elif defined(BFIN)
- int i;
- static const int argreg[] = { PT_R0, PT_R1, PT_R2, PT_R3, PT_R4, PT_R5
};
-
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = ARRAY_SIZE(argreg);
+ static const int argreg[MAX_ARGS] = { PT_R0, PT_R1, PT_R2, PT_R3,
PT_R4, PT_R5 };
for (i = 0; i < tcp->u_nargs; ++i)
if (upeek(tcp, argreg[i], &tcp->u_arg[i]) < 0)
return -1;
# elif defined(SH)
- int i;
- static const int syscall_regs[] = {
- 4 * (REG_REG0+4), 4 * (REG_REG0+5), 4 * (REG_REG0+6), 4 *
(REG_REG0+7),
- 4 * (REG_REG0 ), 4 * (REG_REG0+1), 4 * (REG_REG0+2)
+ static const int syscall_regs[MAX_ARGS] = {
+ 4 * (REG_REG0+4), 4 * (REG_REG0+5), 4 * (REG_REG0+6),
+ 4 * (REG_REG0+7), 4 * (REG_REG0+0), 4 * (REG_REG0+1)
};
- tcp->u_nargs = sysent[tcp->scno].nargs;
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, syscall_regs[i], &tcp->u_arg[i]) < 0)
return -1;
@@ -2145,87 +2087,48 @@ syscall_enter(struct tcb *tcp)
# elif defined(SH64)
int i;
/* Registers used by SH5 Linux system calls for parameters */
- static const int syscall_regs[] = { 2, 3, 4, 5, 6, 7 };
-
- /*
- * TODO: should also check that the number of arguments encoded
- * in the trap number matches the number strace expects.
- */
- /*
- assert(sysent[tcp->scno].nargs < ARRAY_SIZE(syscall_regs));
- */
+ static const int syscall_regs[MAX_ARGS] = { 2, 3, 4, 5, 6, 7 };
- tcp->u_nargs = sysent[tcp->scno].nargs;
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, REG_GENERAL(syscall_regs[i]), &tcp->u_arg[i]) <
0)
return -1;
}
# elif defined(X86_64)
- int i;
static const int argreg[SUPPORTED_PERSONALITIES][MAX_ARGS] = {
{ 8 * RDI, 8 * RSI, 8 * RDX, 8 * R10, 8 * R8 , 8 * R9 }, /*
x86-64 ABI */
{ 8 * RBX, 8 * RCX, 8 * RDX, 8 * RSI, 8 * RDI, 8 * RBP } /*
i386 ABI */
};
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, argreg[current_personality][i], &tcp->u_arg[i])
< 0)
return -1;
}
# elif defined(MICROBLAZE)
- int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = 0;
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, (5 + i) * 4, &tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(CRISV10) || defined(CRISV32)
- int i;
- static const int crisregs[] = {
+ static const int crisregs[MAX_ARGS] = {
4*PT_ORIG_R10, 4*PT_R11, 4*PT_R12,
4*PT_R13 , 4*PT_MOF, 4*PT_SRP
};
- if (tcp->scno >= 0 && tcp->scno < nsyscalls)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = 0;
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, crisregs[i], &tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(TILE)
- int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; ++i) {
if (upeek(tcp, PTREGS_OFFSET_REG(i), &tcp->u_arg[i]) < 0)
return -1;
}
# elif defined(M68K)
- int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, (i < 5 ? i : i + 2)*4, &tcp->u_arg[i]) < 0)
return -1;
}
# else /* Other architecture (like i386) (32bits specific) */
- int i;
- if (tcp->scno >= 0 && tcp->scno < nsyscalls && sysent[tcp->scno].nargs
!= -1)
- tcp->u_nargs = sysent[tcp->scno].nargs;
- else
- tcp->u_nargs = MAX_ARGS;
for (i = 0; i < tcp->u_nargs; i++) {
if (upeek(tcp, i*4, &tcp->u_arg[i]) < 0)
return -1;
--
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