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s390[x]: get rid of syscall_mode, delete code which never triggers

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Before this change, the logic was as follows:
syscall entry:
  get_scno:
    syscall_mode = GPR2
    scno = syscall_mode unless syscall_mode == -ENOSYS
    (if -ENOSYS, scn is retrieved by decoding current insn)
  fixup:
    gpr2 = GPR2
    syscall_mode = scno unless syscall_mode == -ENOSYS
    if (gpr2 != syscall_mode) stray_entry
syscall exit:
  get_res:
    gpr2 = GRP2
  fixup:
    syscall_mode = scno unless syscall_mode == -ENOSYS
    if (WAITEXECVE && gpr2 in (-ENOSYS, scno)) gpr2 = 0;
  get_error:
    gpr2 is retval

Entry fixup's if() can never trigger:
regardless whether GPR2 is -ENOSYS or not, syscall_mode is always
equal to GRP2 value there. So it can be removed.

On sysexit path, syscall mode is never used.

Therefore, syscall_mode variable is deleted. grp2 is read from
GPR2 register in get_scno, redundant read in entry fixup is removed.
As a result, entry fixup's s390 code block vanishes completely.

gpr2 variable is renamed s390_gpr2 to match the convention used
by other arches.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
This commit is contained in:
Denys Vlasenko 2013-07-07 12:47:39 +02:00
parent 8b7aa2b35d
commit f5730e9614
1 changed files with 10 additions and 27 deletions
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37
syscall.c
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@ -755,8 +755,7 @@ static long long mips_r2;
static long mips_a3;
static long mips_r2;
#elif defined(S390) || defined(S390X)
static long gpr2;
static long syscall_mode;
static long s390_gpr2;
#elif defined(HPPA)
static long hppa_r28;
#elif defined(SH)
@ -1127,14 +1126,14 @@ get_scno(struct tcb *tcp)
long scno = 0;
#if defined(S390) || defined(S390X)
if (upeek(tcp->pid, PT_GPR2, &syscall_mode) < 0)
if (upeek(tcp->pid, PT_GPR2, &s390_gpr2) < 0)
return -1;
if (syscall_mode != -ENOSYS) {
if (s390_gpr2 != -ENOSYS) {
/*
* Since kernel version 2.5.44 the scno gets passed in gpr2.
*/
scno = syscall_mode;
scno = s390_gpr2;
} else {
/*
* Old style of "passing" the scno via the SVC instruction.
@ -1596,20 +1595,6 @@ syscall_fixup_on_sysenter(struct tcb *tcp)
return 0;
}
}
#elif defined(S390) || defined(S390X)
/* TODO: we already fetched PT_GPR2 in get_scno
* and stored it in syscall_mode, reuse it here
* instead of re-fetching?
*/
if (upeek(tcp->pid, PT_GPR2, &gpr2) < 0)
return -1;
if (syscall_mode != -ENOSYS)
syscall_mode = tcp->scno;
if (gpr2 != syscall_mode) {
if (debug_flag)
fprintf(stderr, "not a syscall entry (gpr2 = %ld)\n", gpr2);
return 0;
}
#elif defined(M68K)
/* TODO? Eliminate upeek's in arches below like we did in x86 */
if (upeek(tcp->pid, 4*PT_D0, &m68k_d0) < 0)
@ -2066,7 +2051,7 @@ static int
get_syscall_result(struct tcb *tcp)
{
#if defined(S390) || defined(S390X)
if (upeek(tcp->pid, PT_GPR2, &gpr2) < 0)
if (upeek(tcp->pid, PT_GPR2, &s390_gpr2) < 0)
return -1;
#elif defined(POWERPC)
/* already done by get_regs */
@ -2155,16 +2140,14 @@ static void
syscall_fixup_on_sysexit(struct tcb *tcp)
{
#if defined(S390) || defined(S390X)
if (syscall_mode != -ENOSYS)
syscall_mode = tcp->scno;
if ((tcp->flags & TCB_WAITEXECVE)
&& (gpr2 == -ENOSYS || gpr2 == tcp->scno)) {
&& (s390_gpr2 == -ENOSYS || s390_gpr2 == tcp->scno)) {
/*
* Return from execve.
* Fake a return value of zero. We leave the TCB_WAITEXECVE
* flag set for the post-execve SIGTRAP to see and reset.
*/
gpr2 = 0;
s390_gpr2 = 0;
}
#endif
}
@ -2218,12 +2201,12 @@ get_error(struct tcb *tcp)
check_errno = 0;
}
#if defined(S390) || defined(S390X)
if (check_errno && is_negated_errno(gpr2)) {
if (check_errno && is_negated_errno(s390_gpr2)) {
tcp->u_rval = -1;
u_error = -gpr2;
u_error = -s390_gpr2;
}
else {
tcp->u_rval = gpr2;
tcp->u_rval = s390_gpr2;
}
#elif defined(I386)
if (check_errno && is_negated_errno(i386_regs.eax)) {