[POWERPC] 8xx: Move softemu8xx.c from arch/ppc

Previously, Soft_emulate_8xx was called with no implementation, resulting in
build failures whenever building 8xx without math emulation.  The
implementation is copied from arch/ppc to resolve this issue.

However, this sort of minimal emulation is not a very good idea other than
for compatibility with existing userspaces, as it's less efficient than
soft-float and can mislead users into believing they have soft-float.  Thus,
it is made a configurable option, off by default.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

4 files changed, 220 insertions, 1 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 6f5155d8c324..31804575dd5e 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -198,6 +198,17 @@ config MATH_EMULATION
           unit, which will allow programs that use floating-point
           instructions to run.
 
+config 8XX_MINIMAL_FPEMU
+        bool "Minimal math emulation for 8xx"
+        depends on 8xx && !MATH_EMULATION
+        help
+          Older arch/ppc kernels still emulated a few floating point
+          instructions such as load and store, even when full math
+          emulation is disabled.  Say "Y" here if you want to preserve
+          this behavior.
+
+          It is recommended that you build a soft-float userspace instead.
+
 config IOMMU_VMERGE
         bool "Enable IOMMU virtual merging"
         depends on PPC64
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 8327d92eeca8..ca51f0cf27ab 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -75,6 +75,8 @@ obj-$(CONFIG_KEXEC)		+= machine_kexec.o crash.o \
 obj-$(CONFIG_AUDIT)             += audit.o
 obj64-$(CONFIG_AUDIT)           += compat_audit.o
 
+obj-$(CONFIG_8XX_MINIMAL_FPEMU) += softemu8xx.o
+
 ifneq ($(CONFIG_PPC_INDIRECT_IO),y)
 obj-y                           += iomap.o
 endif
diff --git a/arch/powerpc/kernel/softemu8xx.c b/arch/powerpc/kernel/softemu8xx.c
new file mode 100644
index 000000000000..67d6f6890edc
--- /dev/null
+++ b/arch/powerpc/kernel/softemu8xx.c
@@ -0,0 +1,202 @@
+/*
+ * Software emulation of some PPC instructions for the 8xx core.
+ *
+ * Copyright (C) 1998 Dan Malek (dmalek@jlc.net)
+ *
+ * Software floating emuation for the MPC8xx processor.  I did this mostly
+ * because it was easier than trying to get the libraries compiled for
+ * software floating point.  The goal is still to get the libraries done,
+ * but I lost patience and needed some hacks to at least get init and
+ * shells running.  The first problem is the setjmp/longjmp that save
+ * and restore the floating point registers.
+ *
+ * For this emulation, our working registers are found on the register
+ * save area.
+ */
+
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/stddef.h>
+#include <linux/unistd.h>
+#include <linux/ptrace.h>
+#include <linux/slab.h>
+#include <linux/user.h>
+#include <linux/a.out.h>
+#include <linux/interrupt.h>
+
+#include <asm/pgtable.h>
+#include <asm/uaccess.h>
+#include <asm/system.h>
+#include <asm/io.h>
+
+/* Eventually we may need a look-up table, but this works for now.
+*/
+#define LFS     48
+#define LFD     50
+#define LFDU    51
+#define STFD    54
+#define STFDU   55
+#define FMR     63
+
+void print_8xx_pte(struct mm_struct *mm, unsigned long addr)
+{
+        pgd_t *pgd;
+        pmd_t *pmd;
+        pte_t *pte;
+
+        printk(" pte @ 0x%8lx: ", addr);
+        pgd = pgd_offset(mm, addr & PAGE_MASK);
+        if (pgd) {
+                pmd = pmd_offset(pud_offset(pgd, addr & PAGE_MASK),
+                                 addr & PAGE_MASK);
+                if (pmd && pmd_present(*pmd)) {
+                        pte = pte_offset_kernel(pmd, addr & PAGE_MASK);
+                        if (pte) {
+                                printk(" (0x%08lx)->(0x%08lx)->0x%08lx\n",
+                                        (long)pgd, (long)pte, (long)pte_val(*pte));
+#define pp ((long)pte_val(*pte))
+                                printk(" RPN: %05lx PP: %lx SPS: %lx SH: %lx "
+                                       "CI: %lx v: %lx\n",
+                                       pp>>12,    /* rpn */
+                                       (pp>>10)&3, /* pp */
+                                       (pp>>3)&1, /* small */
+                                       (pp>>2)&1, /* shared */
+                                       (pp>>1)&1, /* cache inhibit */
+                                       pp&1       /* valid */
+                                       );
+#undef pp
+                        }
+                        else {
+                                printk("no pte\n");
+                        }
+                }
+                else {
+                        printk("no pmd\n");
+                }
+        }
+        else {
+                printk("no pgd\n");
+        }
+}
+
+int get_8xx_pte(struct mm_struct *mm, unsigned long addr)
+{
+        pgd_t *pgd;
+        pmd_t *pmd;
+        pte_t *pte;
+        int retval = 0;
+
+        pgd = pgd_offset(mm, addr & PAGE_MASK);
+        if (pgd) {
+                pmd = pmd_offset(pud_offset(pgd, addr & PAGE_MASK),
+                                 addr & PAGE_MASK);
+                if (pmd && pmd_present(*pmd)) {
+                        pte = pte_offset_kernel(pmd, addr & PAGE_MASK);
+                        if (pte) {
+                                retval = (int)pte_val(*pte);
+                        }
+                }
+        }
+        return retval;
+}
+
+/*
+ * We return 0 on success, 1 on unimplemented instruction, and EFAULT
+ * if a load/store faulted.
+ */
+int Soft_emulate_8xx(struct pt_regs *regs)
+{
+        u32 inst, instword;
+        u32 flreg, idxreg, disp;
+        int retval;
+        s16 sdisp;
+        u32 *ea, *ip;
+
+        retval = 0;
+
+        instword = *((u32 *)regs->nip);
+        inst = instword >> 26;
+
+        flreg = (instword >> 21) & 0x1f;
+        idxreg = (instword >> 16) & 0x1f;
+        disp = instword & 0xffff;
+
+        ea = (u32 *)(regs->gpr[idxreg] + disp);
+        ip = (u32 *)&current->thread.fpr[flreg];
+
+        switch ( inst )
+        {
+        case LFD:
+                /* this is a 16 bit quantity that is sign extended
+                 * so use a signed short here -- Cort
+                 */
+                sdisp = (instword & 0xffff);
+                ea = (u32 *)(regs->gpr[idxreg] + sdisp);
+                if (copy_from_user(ip, ea, sizeof(double)))
+                        retval = -EFAULT;
+                break;
+
+        case LFDU:
+                if (copy_from_user(ip, ea, sizeof(double)))
+                        retval = -EFAULT;
+                else
+                        regs->gpr[idxreg] = (u32)ea;
+                break;
+        case LFS:
+                sdisp = (instword & 0xffff);
+                ea = (u32 *)(regs->gpr[idxreg] + sdisp);
+                if (copy_from_user(ip, ea, sizeof(float)))
+                        retval = -EFAULT;
+                break;
+        case STFD:
+                /* this is a 16 bit quantity that is sign extended
+                 * so use a signed short here -- Cort
+                 */
+                sdisp = (instword & 0xffff);
+                ea = (u32 *)(regs->gpr[idxreg] + sdisp);
+                if (copy_to_user(ea, ip, sizeof(double)))
+                        retval = -EFAULT;
+                break;
+
+        case STFDU:
+                if (copy_to_user(ea, ip, sizeof(double)))
+                        retval = -EFAULT;
+                else
+                        regs->gpr[idxreg] = (u32)ea;
+                break;
+        case FMR:
+                /* assume this is a fp move -- Cort */
+                memcpy(ip, &current->thread.fpr[(instword>>11)&0x1f],
+                       sizeof(double));
+                break;
+        default:
+                retval = 1;
+                printk("Bad emulation %s/%d\n"
+                       " NIP: %08lx instruction: %08x opcode: %x "
+                       "A: %x B: %x C: %x code: %x rc: %x\n",
+                       current->comm,current->pid,
+                       regs->nip,
+                       instword,inst,
+                       (instword>>16)&0x1f,
+                       (instword>>11)&0x1f,
+                       (instword>>6)&0x1f,
+                       (instword>>1)&0x3ff,
+                       instword&1);
+                {
+                        int pa;
+                        print_8xx_pte(current->mm,regs->nip);
+                        pa = get_8xx_pte(current->mm,regs->nip) & PAGE_MASK;
+                        pa |= (regs->nip & ~PAGE_MASK);
+                        pa = (unsigned long)__va(pa);
+                        printk("Kernel VA for NIP %x ", pa);
+                        print_8xx_pte(current->mm,pa);
+                }
+        }
+
+        if (retval == 0)
+                regs->nip += 4;
+
+        return retval;
+}
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 5a49eabd492e..2f1857c9819f 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -906,7 +906,9 @@ void SoftwareEmulation(struct pt_regs *regs)
 {
         extern int do_mathemu(struct pt_regs *);
         extern int Soft_emulate_8xx(struct pt_regs *);
+#if defined(CONFIG_MATH_EMULATION) || defined(CONFIG_8XX_MINIMAL_FPEMU)
         int errcode;
+#endif
 
         CHECK_FULL_REGS(regs);
 
@@ -936,7 +938,7 @@ void SoftwareEmulation(struct pt_regs *regs)
                 return;
         }
 
-#else
+#elif defined(CONFIG_8XX_MINIMAL_FPEMU)
         errcode = Soft_emulate_8xx(regs);
         switch (errcode) {
         case 0:
@@ -949,6 +951,8 @@ void SoftwareEmulation(struct pt_regs *regs)
                 _exception(SIGSEGV, regs, SEGV_MAPERR, regs->nip);
                 return;
         }
+#else
+        _exception(SIGILL, regs, ILL_ILLOPC, regs->nip);
 #endif
 }
 #endif /* CONFIG_8xx */