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Re: [MIPS] Check FCSR for pending interrupts before restoring from a con

To: vagabon.xyz@gmail.com
Subject: Re: [MIPS] Check FCSR for pending interrupts before restoring from a context.
From: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Date: Fri, 09 Feb 2007 01:54:05 +0900 (JST)
Cc: linux-mips@linux-mips.org, ralf@linux-mips.org, macro@linux-mips.org
In-reply-to: <cda58cb80702080830n44627bafw88b0b6620eefb693@mail.gmail.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20070208.120219.96684712.nemoto@toshiba-tops.co.jp> <20070209.002323.115905985.anemo@mba.ocn.ne.jp> <cda58cb80702080830n44627bafw88b0b6620eefb693@mail.gmail.com>
Sender: linux-mips-bounce@linux-mips.org
On Thu, 8 Feb 2007 17:30:29 +0100, "Franck Bui-Huu" <vagabon.xyz@gmail.com> 
wrote:
> yes this's going to conflict a lot with the patchset I sent...

Here is a patch can be applied on top of your patchset.


Subject: Check FCSR for pending interrupts, alternative version

The commit 6d6671066a311703bca1b91645bb1e04cc983387 is incomplete and
misses non-r4k CPUs.  This patch reverts the commit and fixes in other
way.

* Do FCSR checking in caller of restore_fp_context.
* Send SIGFPE if the signal handler set any FPU exception bits.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
 arch/mips/kernel/r4k_fpu.S       |   16 ------------
 arch/mips/kernel/signal-common.h |    3 ++
 arch/mips/kernel/signal.c        |   46 ++++++++++++++++++++++++++++++++++---
 arch/mips/kernel/signal32.c      |   27 +++++++++++++++++++--
 4 files changed, 70 insertions(+), 22 deletions(-)

diff --git a/arch/mips/kernel/r4k_fpu.S b/arch/mips/kernel/r4k_fpu.S
index 59c1577..dbd42ad 100644
--- a/arch/mips/kernel/r4k_fpu.S
+++ b/arch/mips/kernel/r4k_fpu.S
@@ -114,14 +114,6 @@ LEAF(_save_fp_context32)
  */
 LEAF(_restore_fp_context)
        EX      lw t0, SC_FPC_CSR(a0)
-
-       /* Fail if the CSR has exceptions pending */
-       srl     t1, t0, 5
-       and     t1, t0
-       andi    t1, 0x1f << 7
-       bnez    t1, fault
-        nop
-
 #ifdef CONFIG_64BIT
        EX      ldc1 $f1, SC_FPREGS+8(a0)
        EX      ldc1 $f3, SC_FPREGS+24(a0)
@@ -165,14 +157,6 @@ LEAF(_restore_fp_context)
 LEAF(_restore_fp_context32)
        /* Restore an o32 sigcontext.  */
        EX      lw t0, SC32_FPC_CSR(a0)
-
-       /* Fail if the CSR has exceptions pending */
-       srl     t1, t0, 5
-       and     t1, t0
-       andi    t1, 0x1f << 7
-       bnez    t1, fault
-        nop
-
        EX      ldc1 $f0, SC32_FPREGS+0(a0)
        EX      ldc1 $f2, SC32_FPREGS+16(a0)
        EX      ldc1 $f4, SC32_FPREGS+32(a0)
diff --git a/arch/mips/kernel/signal-common.h b/arch/mips/kernel/signal-common.h
index 9a8abd6..1f24288 100644
--- a/arch/mips/kernel/signal-common.h
+++ b/arch/mips/kernel/signal-common.h
@@ -61,4 +61,7 @@ extern void __user *get_sigframe(struct
  */
 extern int install_sigtramp(unsigned int __user *tramp, unsigned int syscall);
 
+/* Check and clear pending FPU exceptions in saved CSR */
+extern int fpcsr_pending(unsigned int __user *fpcsr);
+
 #endif /* __SIGNAL_COMMON_H */
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 8dfb7b1..d7531d5 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -103,6 +103,37 @@ int setup_sigcontext(struct pt_regs *reg
        return err;
 }
 
+int fpcsr_pending(unsigned int __user *fpcsr)
+{
+       int err, sig = 0;
+       unsigned int csr, enabled;
+
+       err = __get_user(csr, fpcsr);
+       enabled = FPU_CSR_UNI_X | ((csr & FPU_CSR_ALL_E) << 5);
+       /*
+        * If the signal handler set some FPU exceptions, clear it and
+        * send SIGFPE.
+        */
+       if (csr & enabled) {
+               csr &= ~enabled;
+               err |= __put_user(csr, fpcsr);
+               sig = SIGFPE;
+       }
+       return err ?: sig;
+}
+
+static int
+check_and_restore_fp_context(struct sigcontext __user *sc)
+{
+       int err, sig;
+
+       err = sig = fpcsr_pending(&sc->sc_fpc_csr);
+       if (err > 0)
+               err = 0;
+       err |= restore_fp_context(sc);
+       return err ?: sig;
+}
+
 int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 {
        unsigned int used_math;
@@ -137,7 +168,8 @@ int restore_sigcontext(struct pt_regs *r
        if (used_math()) {
                /* restore fpu context if we have used it before */
                own_fpu();
-               err |= restore_fp_context(sc);
+               if (!err)
+                       err = check_and_restore_fp_context(sc);
        } else {
                /* signal handler may have used FPU.  Give it up. */
                lose_fpu();
@@ -307,6 +339,7 @@ asmlinkage void sys_sigreturn(nabi_no_re
 {
        struct sigframe __user *frame;
        sigset_t blocked;
+       int sig;
 
        frame = (struct sigframe __user *) regs.regs[29];
        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -320,8 +353,11 @@ asmlinkage void sys_sigreturn(nabi_no_re
        recalc_sigpending();
        spin_unlock_irq(&current->sighand->siglock);
 
-       if (restore_sigcontext(&regs, &frame->sf_sc))
+       sig = restore_sigcontext(&regs, &frame->sf_sc);
+       if (sig < 0)
                goto badframe;
+       else if (sig)
+               force_sig(sig, current);
 
        /*
         * Don't let your children do this ...
@@ -343,6 +379,7 @@ asmlinkage void sys_rt_sigreturn(nabi_no
        struct rt_sigframe __user *frame;
        sigset_t set;
        stack_t st;
+       int sig;
 
        frame = (struct rt_sigframe __user *) regs.regs[29];
        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -356,8 +393,11 @@ asmlinkage void sys_rt_sigreturn(nabi_no
        recalc_sigpending();
        spin_unlock_irq(&current->sighand->siglock);
 
-       if (restore_sigcontext(&regs, &frame->rs_uc.uc_mcontext))
+       sig = restore_sigcontext(&regs, &frame->rs_uc.uc_mcontext);
+       if (sig < 0)
                goto badframe;
+       else if (sig)
+               force_sig(sig, current);
 
        if (__copy_from_user(&st, &frame->rs_uc.uc_stack, sizeof(st)))
                goto badframe;
diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
index 183fc7e..c37ff65 100644
--- a/arch/mips/kernel/signal32.c
+++ b/arch/mips/kernel/signal32.c
@@ -207,6 +207,18 @@ static int setup_sigcontext32(struct pt_
        return err;
 }
 
+static int
+check_and_restore_fp_context32(struct sigcontext32 __user *sc)
+{
+       int err, sig;
+
+       sig = fpcsr_pending(&sc->sc_fpc_csr);
+       if (sig < 0)
+               err = sig;
+       err |= restore_fp_context32(sc);
+       return err ?: sig;
+}
+
 static int restore_sigcontext32(struct pt_regs *regs,
                                struct sigcontext32 __user *sc)
 {
@@ -242,7 +254,8 @@ static int restore_sigcontext32(struct p
        if (used_math()) {
                /* restore fpu context if we have used it before */
                own_fpu();
-               err |= restore_fp_context32(sc);
+               if (!err)
+                       err = check_and_restore_fp_context32(sc);
        } else {
                /* signal handler may have used FPU.  Give it up. */
                lose_fpu();
@@ -495,6 +508,7 @@ asmlinkage void sys32_sigreturn(nabi_no_
 {
        struct sigframe __user *frame;
        sigset_t blocked;
+       int sig;
 
        frame = (struct sigframe __user *) regs.regs[29];
        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -508,8 +522,11 @@ asmlinkage void sys32_sigreturn(nabi_no_
        recalc_sigpending();
        spin_unlock_irq(&current->sighand->siglock);
 
-       if (restore_sigcontext32(&regs, &frame->sf_sc))
+       sig = restore_sigcontext32(&regs, &frame->sf_sc);
+       if (sig < 0)
                goto badframe;
+       else if (sig)
+               force_sig(sig, current);
 
        /*
         * Don't let your children do this ...
@@ -532,6 +549,7 @@ asmlinkage void sys32_rt_sigreturn(nabi_
        sigset_t set;
        stack_t st;
        s32 sp;
+       int sig;
 
        frame = (struct rt_sigframe32 __user *) regs.regs[29];
        if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
@@ -545,8 +563,11 @@ asmlinkage void sys32_rt_sigreturn(nabi_
        recalc_sigpending();
        spin_unlock_irq(&current->sighand->siglock);
 
-       if (restore_sigcontext32(&regs, &frame->rs_uc.uc_mcontext))
+       sig = restore_sigcontext32(&regs, &frame->rs_uc.uc_mcontext);
+       if (sig < 0)
                goto badframe;
+       else if (sig)
+               force_sig(sig, current);
 
        /* The ucontext contains a stack32_t, so we must convert!  */
        if (__get_user(sp, &frame->rs_uc.uc_stack.ss_sp))

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