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[MIPS] Retry {save,restore}_fp_context if failed in atomic context.

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The save_fp_context()/restore_fp_context() might sleep on accessing
user stack and therefore might lose FPU ownership in middle of them.

If these function failed due to "in_atomic" test in do_page_fault,
touch the sigcontext area in non-atomic context and retry these
save/restore operation.

This is a replacement of a (broken) fix which was titled "Allow CpU
exception in kernel partially".

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Atsushi Nemoto
2007-04-16 23:19:44 +09:00
committed by Ralf Baechle
parent 5323180db7
commit faea623464
4 changed files with 102 additions and 20 deletions
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52
arch/mips/kernel/signal.c
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@@ -20,6 +20,7 @@
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/compiler.h>
#include <linux/uaccess.h>
#include <asm/abi.h>
#include <asm/asm.h>
@@ -27,7 +28,6 @@
#include <asm/cacheflush.h>
#include <asm/fpu.h>
#include <asm/sim.h>
#include <asm/uaccess.h>
#include <asm/ucontext.h>
#include <asm/cpu-features.h>
#include <asm/war.h>
@@ -78,6 +78,46 @@ struct rt_sigframe {
/*
* Helper routines
*/
static int protected_save_fp_context(struct sigcontext __user *sc)
{
int err;
while (1) {
lock_fpu_owner();
own_fpu_inatomic(1);
err = save_fp_context(sc); /* this might fail */
unlock_fpu_owner();
if (likely(!err))
break;
/* touch the sigcontext and try again */
err = __put_user(0, &sc->sc_fpregs[0]) |
__put_user(0, &sc->sc_fpregs[31]) |
__put_user(0, &sc->sc_fpc_csr);
if (err)
break; /* really bad sigcontext */
}
return err;
}
static int protected_restore_fp_context(struct sigcontext __user *sc)
{
int err, tmp;
while (1) {
lock_fpu_owner();
own_fpu_inatomic(0);
err = restore_fp_context(sc); /* this might fail */
unlock_fpu_owner();
if (likely(!err))
break;
/* touch the sigcontext and try again */
err = __get_user(tmp, &sc->sc_fpregs[0]) |
__get_user(tmp, &sc->sc_fpregs[31]) |
__get_user(tmp, &sc->sc_fpc_csr);
if (err)
break; /* really bad sigcontext */
}
return err;
}
int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
int err = 0;
@@ -113,10 +153,7 @@ int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
* Save FPU state to signal context. Signal handler
* will "inherit" current FPU state.
*/
preempt_disable();
own_fpu(1);
err |= save_fp_context(sc);
preempt_enable();
err |= protected_save_fp_context(sc);
}
return err;
}
@@ -148,10 +185,7 @@ check_and_restore_fp_context(struct sigcontext __user *sc)
err = sig = fpcsr_pending(&sc->sc_fpc_csr);
if (err > 0)
err = 0;
preempt_disable();
own_fpu(0);
err |= restore_fp_context(sc);
preempt_enable();
err |= protected_restore_fp_context(sc);
return err ?: sig;
}