[PATCH 2/2] Handle TIF_RESTORE_SIGMASK for i386

From: David Howells
Date: Tue Nov 29 2005 - 16:18:32 EST

The attached patch handles TIF_RESTORE_SIGMASK as added by David Woodhouse's
patch entitled:

[PATCH] 2/3 Add TIF_RESTORE_SIGMASK support for arch/powerpc
[PATCH] 3/3 Generic sys_rt_sigsuspend

It does the following:

(1) Declares TIF_RESTORE_SIGMASK for i386.

(2) Invokes it over to do_signal() when TIF_RESTORE_SIGMASK is set.

(3) Makes do_signal() support TIF_RESTORE_SIGMASK, using the signal mask saved
in current->saved_sigmask.

(4) Discards sys_rt_sigsuspend() from the arch, using the generic one instead.

(5) Makes sys_sigsuspend() save the signal mask and set TIF_RESTORE_SIGMASK
rather than attempting to fudge the return registers.

(6) Makes sys_sigsuspend() return -ERESTARTNOHAND rather than looping
intrinsically.

(7) Makes setup_frame(), setup_rt_frame() and handle_signal() return 0 or
-EFAULT rather than true/false to be consistent with the rest of the
kernel.

Due to the fact do_signal() is then only called from one place:

(8) Makes do_signal() no longer have a return value is it was just being
ignored; force_sig() takes care of this.

(9) Discards the old sigmask argument to do_signal() as it's no longer
necessary.

(10) Makes do_signal() static.

(11) Marks the second argument to do_notify_resume() as unused. The unused
argument should remain in the middle as the arguments are passed in as
registers, and the ordering is specific in entry.S

Given the way do_signal() is now no longer called from sys_{,rt_}sigsuspend(),
they no longer need access to the exception frame, and so can just take
arguments normally.

This patch depends on sys_rt_sigsuspend patch.

Signed-Off-By: David Howells <dhowells@xxxxxxxxxx>
---
warthog>diffstat -p1 i386-tifrestore-2615rc2.diff
arch/i386/kernel/signal.c | 109 ++++++++++++++++++-----------------------
include/asm-i386/signal.h | 1
include/asm-i386/thread_info.h | 2
include/asm-i386/unistd.h | 1
4 files changed, 51 insertions(+), 62 deletions(-)

diff -uNrp linux-2.6.15-rc2-frv-dosignal/arch/i386/kernel/signal.c linux-2.6.15-rc2-frv-tifrestore/arch/i386/kernel/signal.c
--- linux-2.6.15-rc2-frv-dosignal/arch/i386/kernel/signal.c 2005-11-01 13:18:57.000000000 +0000
+++ linux-2.6.15-rc2-frv-tifrestore/arch/i386/kernel/signal.c 2005-11-29 18:43:49.000000000 +0000
@@ -37,51 +37,17 @@
asmlinkage int
sys_sigsuspend(int history0, int history1, old_sigset_t mask)
{
- struct pt_regs * regs = (struct pt_regs *) &history0;
- sigset_t saveset;
-
mask &= _BLOCKABLE;
spin_lock_irq(&current->sighand->siglock);
- saveset = current->blocked;
+ current->saved_sigmask = current->blocked;
siginitset(&current->blocked, mask);
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);

- regs->eax = -EINTR;
- while (1) {
- current->state = TASK_INTERRUPTIBLE;
- schedule();
- if (do_signal(regs, &saveset))
- return -EINTR;
- }
-}
-
-asmlinkage int
-sys_rt_sigsuspend(struct pt_regs regs)
-{
- sigset_t saveset, newset;
-
- /* XXX: Don't preclude handling different sized sigset_t's. */
- if (regs.ecx != sizeof(sigset_t))
- return -EINVAL;
-
- if (copy_from_user(&newset, (sigset_t __user *)regs.ebx, sizeof(newset)))
- return -EFAULT;
- sigdelsetmask(&newset, ~_BLOCKABLE);
-
- spin_lock_irq(&current->sighand->siglock);
- saveset = current->blocked;
- current->blocked = newset;
- recalc_sigpending();
- spin_unlock_irq(&current->sighand->siglock);
-
- regs.eax = -EINTR;
- while (1) {
- current->state = TASK_INTERRUPTIBLE;
- schedule();
- if (do_signal(&regs, &saveset))
- return -EINTR;
- }
+ current->state = TASK_INTERRUPTIBLE;
+ schedule();
+ set_thread_flag(TIF_RESTORE_SIGMASK);
+ return -ERESTARTNOHAND;
}

asmlinkage int
@@ -433,11 +399,11 @@ static int setup_frame(int sig, struct k
current->comm, current->pid, frame, regs->eip, frame->pretcode);
#endif

- return 1;
+ return 0;

give_sigsegv:
force_sigsegv(sig, current);
- return 0;
+ return -EFAULT;
}

static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
@@ -527,11 +493,11 @@ static int setup_rt_frame(int sig, struc
current->comm, current->pid, frame, regs->eip, frame->pretcode);
#endif

- return 1;
+ return 0;

give_sigsegv:
force_sigsegv(sig, current);
- return 0;
+ return -EFAULT;
}

/*
@@ -581,7 +547,7 @@ handle_signal(unsigned long sig, siginfo
else
ret = setup_frame(sig, ka, oldset, regs);

- if (ret) {
+ if (ret == 0) {
spin_lock_irq(&current->sighand->siglock);
sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
if (!(ka->sa.sa_flags & SA_NODEFER))
@@ -598,11 +564,12 @@ handle_signal(unsigned long sig, siginfo
* want to handle. Thus you cannot kill init even with a SIGKILL even by
* mistake.
*/
-int fastcall do_signal(struct pt_regs *regs, sigset_t *oldset)
+static void fastcall do_signal(struct pt_regs *regs)
{
siginfo_t info;
int signr;
struct k_sigaction ka;
+ sigset_t *oldset;

/*
* We want the common case to go fast, which
@@ -613,12 +580,14 @@ int fastcall do_signal(struct pt_regs *r
* CS suffices.
*/
if (!user_mode(regs))
- return 1;
+ return;

if (try_to_freeze())
goto no_signal;

- if (!oldset)
+ if (test_thread_flag(TIF_RESTORE_SIGMASK))
+ oldset = &current->saved_sigmask;
+ else
oldset = &current->blocked;

signr = get_signal_to_deliver(&info, &ka, regs, NULL);
@@ -628,38 +597,55 @@ int fastcall do_signal(struct pt_regs *r
* have been cleared if the watchpoint triggered
* inside the kernel.
*/
- if (unlikely(current->thread.debugreg[7])) {
+ if (unlikely(current->thread.debugreg[7]))
set_debugreg(current->thread.debugreg[7], 7);
- }

/* Whee! Actually deliver the signal. */
- return handle_signal(signr, &info, &ka, oldset, regs);
+ if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
+ /* a signal was successfully delivered; the saved
+ * sigmask will have been stored in the signal frame,
+ * and will be restored by sigreturn, so we can simply
+ * clear the TIF_RESTORE_SIGMASK flag */
+ if (test_thread_flag(TIF_RESTORE_SIGMASK))
+ clear_thread_flag(TIF_RESTORE_SIGMASK);
+ }
+
+ return;
}

- no_signal:
+no_signal:
/* Did we come from a system call? */
if (regs->orig_eax >= 0) {
/* Restart the system call - no handlers present */
- if (regs->eax == -ERESTARTNOHAND ||
- regs->eax == -ERESTARTSYS ||
- regs->eax == -ERESTARTNOINTR) {
+ switch (regs->eax) {
+ case -ERESTARTNOHAND:
+ case -ERESTARTSYS:
+ case -ERESTARTNOINTR:
regs->eax = regs->orig_eax;
regs->eip -= 2;
- }
- if (regs->eax == -ERESTART_RESTARTBLOCK){
+ break;
+
+ case -ERESTART_RESTARTBLOCK:
regs->eax = __NR_restart_syscall;
regs->eip -= 2;
+ break;
}
}
- return 0;
+
+ /* if there's no signal to deliver, we just put the saved sigmask
+ * back */
+ if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
+ clear_thread_flag(TIF_RESTORE_SIGMASK);
+ sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
+ }
}

/*
* notification of userspace execution resumption
- * - triggered by current->work.notify_resume
+ * - triggered by the TIF_WORK_MASK flags
*/
__attribute__((regparm(3)))
-void do_notify_resume(struct pt_regs *regs, sigset_t *oldset,
+void do_notify_resume(struct pt_regs *regs, void *_unused,
__u32 thread_info_flags)
{
/* Pending single-step? */
@@ -667,9 +653,10 @@ void do_notify_resume(struct pt_regs *re
regs->eflags |= TF_MASK;
clear_thread_flag(TIF_SINGLESTEP);
}
+
/* deal with pending signal delivery */
- if (thread_info_flags & _TIF_SIGPENDING)
- do_signal(regs,oldset);
+ if (thread_info_flags & (_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK))
+ do_signal(regs);

clear_thread_flag(TIF_IRET);
}
diff -uNrp linux-2.6.15-rc2-frv-dosignal/include/asm-i386/signal.h linux-2.6.15-rc2-frv-tifrestore/include/asm-i386/signal.h
--- linux-2.6.15-rc2-frv-dosignal/include/asm-i386/signal.h 2005-11-23 12:09:19.000000000 +0000
+++ linux-2.6.15-rc2-frv-tifrestore/include/asm-i386/signal.h 2005-11-29 18:36:53.000000000 +0000
@@ -218,7 +218,6 @@ static __inline__ int sigfindinword(unsi
}

struct pt_regs;
-extern int FASTCALL(do_signal(struct pt_regs *regs, sigset_t *oldset));

#define ptrace_signal_deliver(regs, cookie) \
do { \
diff -uNrp linux-2.6.15-rc2-frv-dosignal/include/asm-i386/thread_info.h linux-2.6.15-rc2-frv-tifrestore/include/asm-i386/thread_info.h
--- linux-2.6.15-rc2-frv-dosignal/include/asm-i386/thread_info.h 2005-11-01 13:19:17.000000000 +0000
+++ linux-2.6.15-rc2-frv-tifrestore/include/asm-i386/thread_info.h 2005-11-29 18:22:21.000000000 +0000
@@ -142,6 +142,7 @@ register unsigned long current_stack_poi
#define TIF_SYSCALL_EMU 6 /* syscall emulation active */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing active */
#define TIF_SECCOMP 8 /* secure computing */
+#define TIF_RESTORE_SIGMASK 9 /* restore signal mask in do_signal() */
#define TIF_POLLING_NRFLAG 16 /* true if poll_idle() is polling TIF_NEED_RESCHED */
#define TIF_MEMDIE 17

@@ -154,6 +155,7 @@ register unsigned long current_stack_poi
#define _TIF_SYSCALL_EMU (1<<TIF_SYSCALL_EMU)
#define _TIF_SYSCALL_AUDIT (1<<TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1<<TIF_SECCOMP)
+#define _TIF_RESTORE_SIGMASK (1<<TIF_RESTORE_SIGMASK)
#define _TIF_POLLING_NRFLAG (1<<TIF_POLLING_NRFLAG)

/* work to do on interrupt/exception return */
diff -uNrp linux-2.6.15-rc2-frv-dosignal/include/asm-i386/unistd.h linux-2.6.15-rc2-frv-tifrestore/include/asm-i386/unistd.h
--- linux-2.6.15-rc2-frv-dosignal/include/asm-i386/unistd.h 2005-11-23 12:09:19.000000000 +0000
+++ linux-2.6.15-rc2-frv-tifrestore/include/asm-i386/unistd.h 2005-11-29 18:21:26.000000000 +0000
@@ -416,6 +416,7 @@ __syscall_return(type,__res); \
#define __ARCH_WANT_SYS_SIGPENDING
#define __ARCH_WANT_SYS_SIGPROCMASK
#define __ARCH_WANT_SYS_RT_SIGACTION
+#define __ARCH_WANT_SYS_RT_SIGSUSPEND
#endif

#ifdef __KERNEL_SYSCALLS__
-
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