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Re: [patch] mips, mips64 signal trampoline

To: linux-mips@linux-mips.org
Subject: Re: [patch] mips, mips64 signal trampoline
From: "Kip Walker" <kwalker@broadcom.com>
Date: Fri, 18 Oct 2002 08:57:02 -0700
Organization: Broadcom Corp. BPBU
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <3DB0266E.810D9D28@broadcom.com>
Sender: linux-mips-bounce@linux-mips.org
OK, the patch was broken because it changed regs->regs[31] before the
setup_sigcontext.  I think this one actually fixes a problem instead of
introducing one.  :-)  Somebody sent the 32-bit part of the patch around
a long time ago, but it doesn't seem to have gotten into CVS yet.

Kip

Kip Walker wrote:
> 
> It looks like the RA setup by setup_frame and setup_rt_frame in
> arch/mips64/kernel/signal.c and signal32.c can be wrong.  Same for
> arch/mips/kernel/signal.c
> 
> signal32.c, 32-bit signal.c: sa_restorer is overriden
> signal.c: regs->regs[31] is pointed at the sigframe's code, even though
> there isn't code in the frame, and a comment says that sa_restorer is
> always used.
> 
> Patch for 2.4 attached.
>
Index: arch/mips/kernel/signal.c
===================================================================
RCS file: /home/cvs/linux/arch/mips/kernel/signal.c,v
retrieving revision 1.39.2.9
diff -u -r1.39.2.9 signal.c
--- arch/mips/kernel/signal.c   5 Aug 2002 23:53:33 -0000       1.39.2.9
+++ arch/mips/kernel/signal.c   18 Oct 2002 15:52:26 -0000
@@ -461,6 +461,7 @@
        int signr, sigset_t *set)
 {
        struct sigframe *frame;
+       unsigned long ra;
        int err = 0;
 
        frame = get_sigframe(ka, regs, sizeof(*frame));
@@ -470,7 +471,7 @@
        /* Set up to return from userspace.  If provided, use a stub already
           in userspace.  */
        if (ka->sa.sa_flags & SA_RESTORER)
-               regs->regs[31] = (unsigned long) ka->sa.sa_restorer;
+               ra = (unsigned long) ka->sa.sa_restorer;
        else {
                /*
                 * Set up the return code ...
@@ -483,6 +484,7 @@
                err |= __put_user(0x0000000c                 ,
                                  frame->sf_code + 1);
                flush_cache_sigtramp((unsigned long) frame->sf_code);
+               ra = (unsigned long) frame->sf_code;
        }
 
        err |= setup_sigcontext(regs, &frame->sf_sc);
@@ -504,13 +506,13 @@
        regs->regs[ 5] = 0;
        regs->regs[ 6] = (unsigned long) &frame->sf_sc;
        regs->regs[29] = (unsigned long) frame;
-       regs->regs[31] = (unsigned long) frame->sf_code;
+       regs->regs[31] = ra;
        regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;
 
 #if DEBUG_SIG
        printk("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%p\n",
               current->comm, current->pid,
-              frame, regs->cp0_epc, frame->sf_code);
+              frame, regs->cp0_epc, regs->regs[31]);
 #endif
         return;
 
@@ -524,6 +526,7 @@
        int signr, sigset_t *set, siginfo_t *info)
 {
        struct rt_sigframe *frame;
+       unsigned long ra;
        int err = 0;
 
        frame = get_sigframe(ka, regs, sizeof(*frame));
@@ -533,7 +536,7 @@
        /* Set up to return from userspace.  If provided, use a stub already
           in userspace.  */
        if (ka->sa.sa_flags & SA_RESTORER)
-               regs->regs[31] = (unsigned long) ka->sa.sa_restorer;
+               ra = (unsigned long) ka->sa.sa_restorer;
        else {
                /*
                 * Set up the return code ...
@@ -546,6 +549,7 @@
                err |= __put_user(0x0000000c                 ,
                                  frame->rs_code + 1);
                flush_cache_sigtramp((unsigned long) frame->rs_code);
+               ra = (unsigned long) frame->rs_code;
        }
 
        /* Create siginfo.  */
@@ -580,13 +584,13 @@
        regs->regs[ 5] = (unsigned long) &frame->rs_info;
        regs->regs[ 6] = (unsigned long) &frame->rs_uc;
        regs->regs[29] = (unsigned long) frame;
-       regs->regs[31] = (unsigned long) frame->rs_code;
+       regs->regs[31] = ra;
        regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;
 
 #if DEBUG_SIG
        printk("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%p\n",
               current->comm, current->pid,
-              frame, regs->cp0_epc, frame->rs_code);
+              frame, regs->cp0_epc, regs->regs[31]);
 #endif
        return;
 
Index: arch/mips64/kernel/signal.c
===================================================================
RCS file: /home/cvs/linux/arch/mips64/kernel/signal.c,v
retrieving revision 1.19.2.5
diff -u -r1.19.2.5 signal.c
--- arch/mips64/kernel/signal.c 18 Sep 2002 13:03:07 -0000      1.19.2.5
+++ arch/mips64/kernel/signal.c 18 Oct 2002 15:52:26 -0000
@@ -313,12 +313,6 @@
        if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
                goto give_sigsegv;
 
-       /*
-        * Set up to return from userspace.  On mips64 we always use a stub 
-        * already provided by userspace and ignore SA_RESTORER.
-        */
-       regs->regs[31] = (unsigned long) ka->sa.sa_restorer;
-
        err |= setup_sigcontext(regs, &frame->sf_sc);
        err |= __copy_to_user(&frame->sf_mask, set, sizeof(*set));
        if (err)
@@ -331,20 +325,21 @@
         *   a1 = 0 (should be cause)
         *   a2 = pointer to struct sigcontext
         *
-        * $25 and c0_epc point to the signal handler, $29 points to the
-        * struct sigframe.
+        * $25 and c0_epc point to the signal handler, $29 points to
+        * the struct sigframe.  On mips64 we always use a stub
+        * already provided by userspace and ignore SA_RESTORER.
         */
        regs->regs[ 4] = signr;
        regs->regs[ 5] = 0;
        regs->regs[ 6] = (unsigned long) &frame->sf_sc;
        regs->regs[29] = (unsigned long) frame;
-       regs->regs[31] = (unsigned long) frame->sf_code;
+       regs->regs[31] = (unsigned long) ka->sa.sa_restorer;
        regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;
 
 #if DEBUG_SIG
        printk("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%p\n",
               current->comm, current->pid,
-              frame, regs->cp0_epc, frame->sf_code);
+              frame, regs->cp0_epc, regs->regs[31]);
 #endif
         return;
 
@@ -364,12 +359,6 @@
        if (!access_ok(VERIFY_WRITE, frame, sizeof (*frame)))
                goto give_sigsegv;
 
-       /*
-        * Set up to return from userspace.  On mips64 we always use a stub 
-        * already provided by userspace and ignore SA_RESTORER.
-        */
-       regs->regs[31] = (unsigned long) ka->sa.sa_restorer;
-
        /* Create siginfo.  */
        err |= copy_siginfo_to_user(&frame->rs_info, info);
 
@@ -396,19 +385,20 @@
         *   a2 = pointer to ucontext
         *
         * $25 and c0_epc point to the signal handler, $29 points to
-        * the struct rt_sigframe.
+        * the struct rt_sigframe.  On mips64 we always use a stub
+        * already provided by userspace and ignore SA_RESTORER.
         */
        regs->regs[ 4] = signr;
        regs->regs[ 5] = (unsigned long) &frame->rs_info;
        regs->regs[ 6] = (unsigned long) &frame->rs_uc;
        regs->regs[29] = (unsigned long) frame;
-       regs->regs[31] = (unsigned long) frame->rs_code;
+       regs->regs[31] = (unsigned long) ka->sa.sa_restorer;
        regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;
 
 #if DEBUG_SIG
        printk("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%p\n",
               current->comm, current->pid,
-              frame, regs->cp0_epc, frame->rs_code);
+              frame, regs->cp0_epc, regs->regs[31]);
 #endif
        return;
 
Index: arch/mips64/kernel/signal32.c
===================================================================
RCS file: /home/cvs/linux/arch/mips64/kernel/signal32.c,v
retrieving revision 1.20.2.9
diff -u -r1.20.2.9 signal32.c
--- arch/mips64/kernel/signal32.c       2 Oct 2002 12:21:45 -0000       1.20.2.9
+++ arch/mips64/kernel/signal32.c       18 Oct 2002 15:52:26 -0000
@@ -567,6 +567,7 @@
                               int signr, sigset_t *set)
 {
        struct sigframe *frame;
+       unsigned long ra;
        int err = 0;
 
        frame = get_sigframe(ka, regs, sizeof(*frame));
@@ -576,7 +577,7 @@
        /* Set up to return from userspace.  If provided, use a stub already
           in userspace.  */
        if (ka->sa.sa_flags & SA_RESTORER)
-               regs->regs[31] = (unsigned long) ka->sa.sa_restorer;
+               ra = (unsigned long) ka->sa.sa_restorer;
        else {
                /*
                 * Set up the return code ...
@@ -589,6 +590,7 @@
                err |= __put_user(0x0000000c                 ,
                                  frame->sf_code + 1);
                flush_cache_sigtramp((unsigned long) frame->sf_code);
+               ra = (unsigned long) frame->sf_code;
        }
 
        err |= setup_sigcontext(regs, &frame->sf_sc);
@@ -610,13 +612,13 @@
        regs->regs[ 5] = 0;
        regs->regs[ 6] = (unsigned long) &frame->sf_sc;
        regs->regs[29] = (unsigned long) frame;
-       regs->regs[31] = (unsigned long) frame->sf_code;
+       regs->regs[31] = ra;
        regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;
 
 #if DEBUG_SIG
        printk("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%p\n",
               current->comm, current->pid,
-              frame, regs->cp0_epc, frame->sf_code);
+              frame, regs->cp0_epc, regs->regs[31]);
 #endif
         return;
 
@@ -631,6 +633,7 @@
                                  sigset_t *set, siginfo_t *info)
 {
        struct rt_sigframe32 *frame;
+       unsigned long ra;
        int err = 0;
 
        frame = get_sigframe(ka, regs, sizeof(*frame));
@@ -640,7 +643,7 @@
        /* Set up to return from userspace.  If provided, use a stub already
           in userspace.  */
        if (ka->sa.sa_flags & SA_RESTORER)
-               regs->regs[31] = (unsigned long) ka->sa.sa_restorer;
+               ra = (unsigned long) ka->sa.sa_restorer;
        else {
                /*
                 * Set up the return code ...
@@ -653,6 +656,7 @@
                err |= __put_user(0x0000000c                 ,
                                  frame->rs_code + 1);
                flush_cache_sigtramp((unsigned long) frame->rs_code);
+               ra = (unsigned long) frame->rs_code;
        }
 
        /* Convert (siginfo_t -> siginfo_t32) and copy to user. */
@@ -687,13 +691,13 @@
        regs->regs[ 5] = (unsigned long) &frame->rs_info;
        regs->regs[ 6] = (unsigned long) &frame->rs_uc;
        regs->regs[29] = (unsigned long) frame;
-       regs->regs[31] = (unsigned long) frame->rs_code;
+       regs->regs[31] = ra;
        regs->cp0_epc = regs->regs[25] = (unsigned long) ka->sa.sa_handler;
 
 #if DEBUG_SIG
        printk("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%p\n",
               current->comm, current->pid,
-              frame, regs->cp0_epc, frame->rs_code);
+              frame, regs->cp0_epc, regs->regs[31]);
 #endif
        return;
 
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