openrisc: Support floating point user api

Add support for handling floating point exceptions and forwarding the
SIGFPE signal to processes.  Also, add fpu state to sigcontext.

Signed-off-by: Stafford Horne <shorne@gmail.com>

Author: stffrdhrn

arch/openrisc/include/uapi/asm/elf.h

@@ -53,8 +53,7 @@ typedef unsigned long elf_greg_t;
 #define ELF_NGREG (sizeof(struct user_regs_struct) / sizeof(elf_greg_t))
 typedef elf_greg_t elf_gregset_t[ELF_NGREG];
 
-/* A placeholder; OR32 does not have fp support yes, so no fp regs for now.  */
-typedef unsigned long elf_fpregset_t;
+typedef struct __or1k_fpu_state elf_fpregset_t;
 
 /* EM_OPENRISC is defined in linux/elf-em.h */
 #define EM_OR32         0x8472

arch/openrisc/include/uapi/asm/ptrace.h

@@ -30,6 +30,10 @@ struct user_regs_struct {
 	unsigned long pc;
 	unsigned long sr;
 };
+
+struct __or1k_fpu_state {
+	unsigned long fpcsr;
+};
 #endif
 
 

arch/openrisc/include/uapi/asm/sigcontext.h

@@ -28,6 +28,7 @@
 
 struct sigcontext {
 	struct user_regs_struct regs;  /* needs to be first */
+	struct __or1k_fpu_state fpu;
 	unsigned long oldmask;
 };
 

arch/openrisc/kernel/entry.S

@@ -848,9 +848,16 @@ _syscall_badsys:
 
 /******* END SYSCALL HANDLING *******/
 
-/* ---[ 0xd00: Trap exception ]------------------------------------------ */
+/* ---[ 0xd00: Floating Point exception ]-------------------------------- */
 
-UNHANDLED_EXCEPTION(_vector_0xd00,0xd00)
+EXCEPTION_ENTRY(_fpe_trap_handler)
+	CLEAR_LWA_FLAG(r3)
+	/* r4: EA of fault (set by EXCEPTION_HANDLE) */
+	l.jal   do_fpe_trap
+	 l.addi  r3,r1,0 /* pt_regs */
+
+	l.j     _ret_from_exception
+	 l.nop
 
 /* ---[ 0xe00: Trap exception ]------------------------------------------ */
 

arch/openrisc/kernel/head.S

@@ -424,9 +424,9 @@ _dispatch_do_ipage_fault:
     .org 0xc00
 	EXCEPTION_HANDLE(_sys_call_handler)
 
-/* ---[ 0xd00: Trap exception ]------------------------------------------ */
+/* ---[ 0xd00: Floating point exception ]--------------------------------- */
     .org 0xd00
-	UNHANDLED_EXCEPTION(_vector_0xd00)
+	EXCEPTION_HANDLE(_fpe_trap_handler)
 
 /* ---[ 0xe00: Trap exception ]------------------------------------------ */
     .org 0xe00

arch/openrisc/kernel/signal.c

@@ -50,6 +50,7 @@ static int restore_sigcontext(struct pt_regs *regs,
 	err |= __copy_from_user(regs, sc->regs.gpr, 32 * sizeof(unsigned long));
 	err |= __copy_from_user(&regs->pc, &sc->regs.pc, sizeof(unsigned long));
 	err |= __copy_from_user(&regs->sr, &sc->regs.sr, sizeof(unsigned long));
+	err |= __copy_from_user(&regs->fpcsr, &sc->fpu.fpcsr, sizeof(unsigned long));
 
 	/* make sure the SM-bit is cleared so user-mode cannot fool us */
 	regs->sr &= ~SPR_SR_SM;
@@ -112,6 +113,7 @@ static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 	err |= __copy_to_user(sc->regs.gpr, regs, 32 * sizeof(unsigned long));
 	err |= __copy_to_user(&sc->regs.pc, &regs->pc, sizeof(unsigned long));
 	err |= __copy_to_user(&sc->regs.sr, &regs->sr, sizeof(unsigned long));
+	err |= __copy_to_user(&sc->fpu.fpcsr, &regs->fpcsr, sizeof(unsigned long));
 
 	return err;
 }

arch/openrisc/kernel/traps.c

@@ -243,6 +243,28 @@ asmlinkage void unhandled_exception(struct pt_regs *regs, int ea, int vector)
 	die("Oops", regs, 9);
 }
 
+asmlinkage void do_fpe_trap(struct pt_regs *regs, unsigned long address)
+{
+	int code = FPE_FLTUNK;
+	unsigned long fpcsr = regs->fpcsr;
+
+	if (fpcsr & SPR_FPCSR_IVF)
+		code = FPE_FLTINV;
+	else if (fpcsr & SPR_FPCSR_OVF)
+		code = FPE_FLTOVF;
+	else if (fpcsr & SPR_FPCSR_UNF)
+		code = FPE_FLTUND;
+	else if (fpcsr & SPR_FPCSR_DZF)
+		code = FPE_FLTDIV;
+	else if (fpcsr & SPR_FPCSR_IXF)
+		code = FPE_FLTRES;
+
+	/* Clear all flags */
+	regs->fpcsr &= ~SPR_FPCSR_ALLF;
+
+	force_sig_fault(SIGFPE, code, (void __user *)regs->pc);
+}
+
 asmlinkage void do_trap(struct pt_regs *regs, unsigned long address)
 {
 	force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->pc);