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SubjectRe: [alpha] cleanup opDEC workaround
On Wed, Nov 21, 2001 at 03:15:55PM +0300, Ivan Kokshaysky wrote:
> > I suppose the other alternative to get the testing code out of
> > the normal entIF is to create a custom entIF that is installed
> > only during opDEC testing. Seems too much work...
>
> Agreed. Alternatively, it's possible to hack dummy_emul(), which
> doesn't affect the normal case.

Actually, the custom entIF isn't that much work. What about this?


r~



--- traps.c.orig Wed Nov 21 14:13:31 2001
+++ traps.c Wed Nov 21 14:25:22 2001
@@ -24,31 +24,35 @@

#include "proto.h"

-/* data/code implementing a work-around for some SRMs which
- mishandle opDEC faults
-*/
-static int opDEC_testing = 0;
-static int opDEC_fix = 0;
-static unsigned long opDEC_test_pc = 0;
+/* Work-around for some SRMs which mishandle opDEC faults. */
+static int opDEC_fix;

-static void
+extern void opDEC_check_entIF(void);
+asm(".section .text.init,\"ax\" \n\
+ .ent opDEC_check_entIF \n\
+opDEC_check_entIF: \n\
+ ldq $16,8($sp) \n\
+ call_pal 63 /* PAL_rti */ \n\
+ .end opDEC_check_entIF \n\
+ .previous");
+
+static void __init
opDEC_check(void)
{
- unsigned long test_pc;
+ long diff;

- lock_kernel();
- opDEC_testing = 1;
+ wrent(opDEC_check_entIF, 3);

__asm__ __volatile__(
- " br %0,1f\n"
- "1: addq %0,8,%0\n"
- " stq %0,%1\n"
- " cvttq/svm $f31,$f31\n"
- : "=&r"(test_pc), "=m"(opDEC_test_pc)
- : );
-
- opDEC_testing = 0;
- unlock_kernel();
+ "br %0,1f\n"
+ "1:\n\t"
+ "cvttq/svm $f31, $f31\n\t"
+ "subq $16, %0, %0"
+ : "=r"(diff) : : "$16");
+
+ opDEC_fix = 4 - diff;
+ if (opDEC_fix)
+ printk("opDEC fixup enabled.\n");
}

void
@@ -231,24 +235,22 @@
unsigned long a2, unsigned long a3, unsigned long a4,
unsigned long a5, struct pt_regs regs)
{
- if (!opDEC_testing || type != 4) {
- die_if_kernel((type == 1 ? "Kernel Bug" : "Instruction fault"),
- &regs, type, 0);
- }
-
switch (type) {
- case 0: /* breakpoint */
+ case 0: /* breakpoint */
+ die_if_kernel("Breakpoint fault", &regs, type, 0);
if (ptrace_cancel_bpt(current)) {
regs.pc -= 4; /* make pc point to former bpt */
}
send_sig(SIGTRAP, current, 1);
return;

- case 1: /* bugcheck */
+ case 1: /* bugcheck */
+ die_if_kernel("Kernel Bug", &regs, type, 0);
send_sig(SIGTRAP, current, 1);
return;

- case 2: /* gentrap */
+ case 2: /* gentrap */
+ die_if_kernel("Divide by zero fault", &regs, type, 0);
/*
* The exception code should be passed on to the signal
* handler as the second argument. Linux doesn't do that
@@ -285,27 +287,14 @@
}
break;

- case 4: /* opDEC */
+ case 4: /* opDEC */
if (implver() == IMPLVER_EV4) {
- /* The some versions of SRM do not handle
- the opDEC properly - they return the PC of the
- opDEC fault, not the instruction after as the
- Alpha architecture requires. Here we fix it up.
- We do this by intentionally causing an opDEC
- fault during the boot sequence and testing if
- we get the correct PC. If not, we set a flag
- to correct it every time through.
- */
- if (opDEC_testing) {
- if (regs.pc == opDEC_test_pc) {
- opDEC_fix = 4;
- regs.pc += 4;
- printk("opDEC fixup enabled.\n");
- }
- return;
- }
+ /* Some versions of SRM do not handle opDEC properly.
+ They return the PC of the opDEC fault, not the
+ instruction after the fault as the architecture
+ requires. Here we fix it up. */
regs.pc += opDEC_fix;
-
+
/* EV4 does not implement anything except normal
rounding. Everything else will come here as
an illegal instruction. Emulate them. */
@@ -314,7 +303,7 @@
}
break;

- case 3: /* FEN fault */
+ case 3: /* FEN fault */
/* Irritating users can call PAL_clrfen to disable the
FPU for the process. The kernel will then trap in
do_switch_stack and undo_switch_stack when we try
@@ -328,10 +317,12 @@
__reload_thread(&current->thread);
return;

- case 5: /* illoc */
- default: /* unexpected instruction-fault type */
- ;
+ case 5: /* illoc */
+ default: /* unexpected instruction-fault type */
+ break;
}
+
+ die_if_kernel("Instruction fault", &regs, type, 0);
send_sig(SIGILL, current, 1);
}

@@ -999,24 +990,22 @@
return -ENOSYS;
}

-void
+void __init
trap_init(void)
{
/* Tell PAL-code what global pointer we want in the kernel. */
register unsigned long gptr __asm__("$29");
wrkgp(gptr);

+ /* Hack for Multia (UDB) and JENSEN: some of their SRMs have
+ a bug in the handling of the opDEC fault. Fix it up if so. */
+ if (implver() == IMPLVER_EV4)
+ opDEC_check();
+
wrent(entArith, 1);
wrent(entMM, 2);
wrent(entIF, 3);
wrent(entUna, 4);
wrent(entSys, 5);
wrent(entDbg, 6);
-
- /* Hack for Multia (UDB) and JENSEN: some of their SRMs have
- * a bug in the handling of the opDEC fault. Fix it up if so.
- */
- if (implver() == IMPLVER_EV4) {
- opDEC_check();
- }
}
-
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