Display mask on enter to sigreturn, not on exit

sys_sigreturn() performs ugly manipulations in order to show
signal mask which is restored by this syscall: on syscall entry,
fetches it from the stack, saves it in tcp->u_arg[]
(where it used to overflow this array - fixed sometime ago),
then retrieves the mask and displays it on syscall exit.

Apparently, the motivation is to make it slightly more obvious
to user that signal mask is restored only when this syscall returns.
IMO, this hardly justifies the necessary hacks. It is much easier
to display the mask at the point when we fetch it - on syscall entry.

While at it, I made it so that we do display returned value/errno.
I see no point in hiding it and showing uninformative "= ?" instead.

Example of pause() being interrupted by ALRM which has installed handler
which re-arms ALRM:

Before the patch:

rt_sigsuspend([INT])                    = ? ERESTARTNOHAND (To be restarted)
--- {si_signo=SIGALRM, si_code=SI_KERNEL} (Alarm clock) ---
alarm(1)                                = 0
sigreturn()                             = ? (mask now [INT])

After:

rt_sigsuspend([INT])                    = ? ERESTARTNOHAND (To be restarted)
--- {si_signo=SIGALRM, si_code=SI_KERNEL} (Alarm clock) ---
alarm(1)                                = 0
sigreturn() (mask [INT])                = -1 EINTR (Interrupted system call)

* defs.h: Declare struct pt_regs i386_regs and struct pt_regs x86_64_regs.
* syscall.c: Remove "static" keywork from these structures' definitions.
* signal.c (sys_sigreturn): Display mask on enter, not on exit.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>

diff --git a/defs.h b/defs.h
index 2f4c98ba0d7ca5e99eade0aed47c96a9feca3a63..22383730fd04a383f11fc2892e319ede8a2dd170 100644 (file)
--- a/defs.h
+++ b/defs.h
@@ -391,6 +391,14 @@ extern int mp_ioctl(int f, int c, void *a, int s);
 
 #define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
 
+#ifdef LINUX
+# if defined(I386)
+struct pt_regs i386_regs;
+# elif defined(X86_64)
+struct pt_regs x86_64_regs;
+# endif
+#endif /* LINUX */
+
 /* Trace Control Block */
 struct tcb {
        int flags;              /* See below for TCB_ values */

diff --git a/signal.c b/signal.c
index 1e36973b2974997070a68c87996fd5bd9a28dc5e..11396bd7616d94fe76e65eeeb0003b72083302cf 100644 (file)
--- a/signal.c
+++ b/signal.c
@@ -1117,95 +1117,63 @@ sys_sigreturn(struct tcb *tcp)
        if (entering(tcp)) {
                struct pt_regs regs;
                struct sigcontext_struct sc;
-               tcp->u_arg[0] = 0;
+               sigset_t sigm;
                if (ptrace(PTRACE_GETREGS, tcp->pid, NULL, (void *)&regs) == -1)
                        return 0;
                if (umove(tcp, regs.ARM_sp, &sc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = sc.oldmask;
-       } else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(sc.oldmask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined(S390) || defined(S390X)
        if (entering(tcp)) {
                long usp;
                struct sigcontext_struct sc;
-               tcp->u_arg[0] = 0;
                if (upeek(tcp, PT_GPR15, &usp) < 0)
                        return 0;
-               if (umove(tcp, usp+__SIGNAL_FRAMESIZE, &sc) < 0)
+               if (umove(tcp, usp + __SIGNAL_FRAMESIZE, &sc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               memcpy(&tcp->u_arg[1], &sc.oldmask[0], NSIG / 8);
-       } else {
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               tcp->auxstr = sprintsigmask("mask now ", (sigset_t *)&tcp->u_arg[1], 0);
-               return RVAL_NONE | RVAL_STR;
+               tprints(sprintsigmask(") (mask ", (sigset_t *)&sc.oldmask[0], 0);
        }
        return 0;
 #elif defined(I386)
        if (entering(tcp)) {
-               long esp;
                struct sigcontext_struct sc;
-               tcp->u_arg[0] = 0;
-               if (upeek(tcp, 4*UESP, &esp) < 0)
-                       return 0;
-               if (umove(tcp, esp, &sc) < 0)
-                       return 0;
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = sc.oldmask;
-       }
-       else {
+               /* Note: on i386, sc is followed on stack by struct fpstate
+                * and after it an additional u32 extramask[1] which holds
+                * upper half of the mask. We can fetch it there
+                * if/when we'd want to display the full mask...
+                */
                sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
+               if (umove(tcp, i386_regs.esp, &sc) < 0)
                        return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(sc.oldmask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0));
        }
        return 0;
 #elif defined(IA64)
        if (entering(tcp)) {
                struct sigcontext sc;
                long sp;
+               sigset_t sigm;
                /* offset of sigcontext in the kernel's sigframe structure: */
 #              define SIGFRAME_SC_OFFSET       0x90
-               tcp->u_arg[0] = 0;
                if (upeek(tcp, PT_R12, &sp) < 0)
                        return 0;
                if (umove(tcp, sp + 16 + SIGFRAME_SC_OFFSET, &sc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               memcpy(tcp->u_arg + 1, &sc.sc_mask, NSIG / 8);
-       }
-       else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
                sigemptyset(&sigm);
-               memcpy(&sigm, tcp->u_arg + 1, NSIG / 8);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               memcpy(&sigm, &sc.sc_mask, NSIG / 8);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined(POWERPC)
        if (entering(tcp)) {
                long esp;
                struct sigcontext_struct sc;
-               tcp->u_arg[0] = 0;
-               if (upeek(tcp, sizeof(unsigned long)*PT_R1, &esp) < 0)
+               sigset_t sigm;
+               if (upeek(tcp, sizeof(unsigned long) * PT_R1, &esp) < 0)
                        return 0;
                /* Skip dummy stack frame. */
 #ifdef POWERPC64
@@ -1218,61 +1186,34 @@ sys_sigreturn(struct tcb *tcp)
 #endif
                if (umove(tcp, esp, &sc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = sc.oldmask;
-       }
-       else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(sc.oldmask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined(M68K)
        if (entering(tcp)) {
                long usp;
                struct sigcontext sc;
-               tcp->u_arg[0] = 0;
+               sigset_t sigm;
                if (upeek(tcp, 4*PT_USP, &usp) < 0)
                        return 0;
                if (umove(tcp, usp, &sc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = sc.sc_mask;
-       }
-       else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(sc.sc_mask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined(ALPHA)
        if (entering(tcp)) {
                long fp;
                struct sigcontext_struct sc;
-               tcp->u_arg[0] = 0;
+               sigset_t sigm;
                if (upeek(tcp, REG_FP, &fp) < 0)
                        return 0;
                if (umove(tcp, fp, &sc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = sc.sc_mask;
-       }
-       else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(sc.sc_mask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined (SPARC) || defined (SPARC64)
@@ -1280,7 +1221,7 @@ sys_sigreturn(struct tcb *tcp)
                long i1;
                struct pt_regs regs;
                m_siginfo_t si;
-               tcp->u_arg[0] = 0;
+               sigset_t sigm;
                if (ptrace(PTRACE_GETREGS, tcp->pid, (char *)&regs, 0) < 0) {
                        perror("sigreturn: PTRACE_GETREGS");
                        return 0;
@@ -1290,16 +1231,8 @@ sys_sigreturn(struct tcb *tcp)
                        perror("sigreturn: umove");
                        return 0;
                }
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = si.si_mask;
-       } else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(si.si_mask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined (LINUX_MIPSN32) || defined (LINUX_MIPSN64)
@@ -1308,23 +1241,15 @@ sys_sigreturn(struct tcb *tcp)
        if (entering(tcp)) {
                long sp;
                struct ucontext uc;
-               tcp->u_arg[0] = 0;
+               sigset_t sigm;
                if (upeek(tcp, REG_SP, &sp) < 0)
                        return 0;
                /* There are six words followed by a 128-byte siginfo.  */
                sp = sp + 6 * 4 + 128;
                if (umove(tcp, sp, &uc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = *(long *) &uc.uc_sigmask;
-       } else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(*(long *) &uc.uc_sigmask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined(MIPS)
@@ -1332,7 +1257,7 @@ sys_sigreturn(struct tcb *tcp)
                long sp;
                struct pt_regs regs;
                m_siginfo_t si;
-               tcp->u_arg[0] = 0;
+               sigset_t sigm;
                if (ptrace(PTRACE_GETREGS, tcp->pid, (char *)&regs, 0) < 0) {
                        perror("sigreturn: PTRACE_GETREGS");
                        return 0;
@@ -1340,65 +1265,40 @@ sys_sigreturn(struct tcb *tcp)
                sp = regs.regs[29];
                if (umove(tcp, sp, &si) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = si.si_mask;
-       } else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(si.si_mask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined(CRISV10) || defined(CRISV32)
        if (entering(tcp)) {
                struct sigcontext sc;
                long regs[PT_MAX+1];
-               tcp->u_arg[0] = 0;
+               sigset_t sigm;
                if (ptrace(PTRACE_GETREGS, tcp->pid, NULL, (long)regs) < 0) {
                        perror("sigreturn: PTRACE_GETREGS");
                        return 0;
                }
                if (umove(tcp, regs[PT_USP], &sc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = sc.oldmask;
-       } else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(sc.oldmask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined(TILE)
        if (entering(tcp)) {
                struct ucontext uc;
                long sp;
+               sigset_t sigm;
 
                /* offset of ucontext in the kernel's sigframe structure */
 #              define SIGFRAME_UC_OFFSET C_ABI_SAVE_AREA_SIZE + sizeof(struct siginfo)
-               tcp->u_arg[0] = 0;
                if (upeek(tcp, PTREGS_OFFSET_SP, &sp) < 0)
                        return 0;
                if (umove(tcp, sp + SIGFRAME_UC_OFFSET, &uc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               memcpy(tcp->u_arg + 1, &uc.uc_sigmask, NSIG / 8);
-       }
-       else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
                sigemptyset(&sigm);
-               memcpy(&sigm, tcp->u_arg + 1, NSIG / 8);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               memcpy(&sigm, &uc.uc_sigmask, NSIG / 8);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #elif defined(MICROBLAZE)
@@ -1406,22 +1306,14 @@ sys_sigreturn(struct tcb *tcp)
        if (entering(tcp)) {
                struct sigcontext sc;
                long sp;
-               tcp->u_arg[0] = 0;
+               sigset_t sigm;
                /* Read r1, the stack pointer.  */
                if (upeek(tcp, 1 * 4, &sp) < 0)
                        return 0;
                if (umove(tcp, sp, &sc) < 0)
                        return 0;
-               tcp->u_arg[0] = 1;
-               tcp->u_arg[1] = sc.oldmask;
-       } else {
-               sigset_t sigm;
-               tcp->u_rval = tcp->u_error = 0;
-               if (tcp->u_arg[0] == 0)
-                       return 0;
-               long_to_sigset(tcp->u_arg[1], &sigm);
-               tcp->auxstr = sprintsigmask("mask now ", &sigm, 0);
-               return RVAL_NONE | RVAL_STR;
+               long_to_sigset(sc.oldmask, &sigm);
+               tprints(sprintsigmask(") (mask ", &sigm, 0);
        }
        return 0;
 #else

diff --git a/syscall.c b/syscall.c
index ec3eaab77103a53bd9bc2687d9de81b04e461cb2..b103d3482e87776021da3a5d93f8071e491c9590 100644 (file)
--- a/syscall.c
+++ b/syscall.c
@@ -734,10 +734,10 @@ is_restart_error(struct tcb *tcp)
 struct tcb *tcp_last = NULL;
 
 #ifdef LINUX
-# if defined (I386)
-static struct pt_regs i386_regs;
+# if defined(I386)
+struct pt_regs i386_regs;
 # elif defined(X86_64)
-static struct pt_regs x86_64_regs;
+struct pt_regs x86_64_regs;
 # elif defined (IA64)
 long r8, r10, psr; /* TODO: make static? */
 long ia32 = 0; /* not static */