This is a compromising fix for sysmips(MIPS_ATOMIC_SET, ...).  It
forces SIGSYS when the return value is a small negative value.  This
limit is OK for glibc.

This patches works for CPUs both with ll/sc and without ll/sc.

Derived from Maceij's sys_test_and_set patch.

Jun

diff -Nru linux/arch/mips/kernel/sysmips.c.orig linux/arch/mips/kernel/sysmips.c
--- linux/arch/mips/kernel/sysmips.c.orig	Mon Apr 23 11:32:54 2001
+++ linux/arch/mips/kernel/sysmips.c	Tue Jun 26 11:50:48 2001
@@ -16,7 +16,7 @@
 #include <linux/sched.h>
 #include <linux/string.h>
 #include <linux/utsname.h>
-
+#include <linux/signal.h>
 #include <asm/cachectl.h>
 #include <asm/pgalloc.h>
 #include <asm/sysmips.h>
@@ -75,53 +75,83 @@
 	}
 
 	case MIPS_ATOMIC_SET: {
-#ifdef CONFIG_CPU_HAS_LLSC
-		unsigned int tmp;
+		int *ptr, val, ret, err, tmp;
+		struct siginfo info;
 
-		p = (int *) arg1;
-		errno = verify_area(VERIFY_WRITE, p, sizeof(*p));
-		if (errno)
-			return errno;
-		errno = 0;
-
-		__asm__(".set\tpush\t\t\t# sysmips(MIPS_ATOMIC, ...)\n\t"
-			".set\tmips2\n\t"
-			".set\tnoat\n\t"
-			"1:\tll\t%0, %4\n\t"
-			"move\t$1, %3\n\t"
-			"2:\tsc\t$1, %1\n\t"
-			"beqz\t$1, 1b\n\t"
-			".set\tpop\n\t"
-			".section\t.fixup,\"ax\"\n"
-			"3:\tli\t%2, 1\t\t\t# error\n\t"
-			".previous\n\t"
-			".section\t__ex_table,\"a\"\n\t"
-			".word\t1b, 3b\n\t"
-			".word\t2b, 3b\n\t"
-			".previous\n\t"
-			: "=&r" (tmp), "=o" (* (u32 *) p), "=r" (errno)
-			: "r" (arg2), "o" (* (u32 *) p), "2" (errno)
-			: "$1");
+		ptr = (int *)arg1;
+		val = (int)arg2;
 
-		if (errno)
-			return -EFAULT;
+		/* Don't emulate unaligned accesses. */
+		if ((int)ptr & 3) {
+			info.si_signo = SIGBUS;
+                        info.si_code = BUS_ADRALN;
+			goto fault;
+		}
+
+		/* A zero here saves us three instructions. */
+		err = verify_area(VERIFY_WRITE, ptr, 0);
+		if (err) {
+                        info.si_signo = SIGSEGV;
+			info.si_code = SEGV_ACCERR;
+			goto fault;
+		}
 
-		/* We're skipping error handling etc.  */
-		if (current->ptrace & PT_TRACESYS)
-			syscall_trace();
-
-		((struct pt_regs *)&cmd)->regs[2] = tmp;
-		((struct pt_regs *)&cmd)->regs[7] = 0;
-
-		__asm__ __volatile__(
-			"move\t$29, %0\n\t"
-			"j\to32_ret_from_sys_call"
-			: /* No outputs */
-			: "r" (&cmd));
-		/* Unreached */
+#ifdef CONFIG_CPU_HAS_LLSC
+		__asm__(".set   mips2\n\t"
+			"1:\n\t"
+			"ll     %0,%5\n\t"
+	                ".set   push\n\t"
+	                ".set   noreorder\n\t"
+	                "beq    %0,%4,3f\n\t"
+	                " move  %3,%4\n"
+	                ".set   pop\n\t"
+	                "2:\n\t"
+	                "sc     %3,%1\n\t"
+	                "beqz   %3,1b\n\t"
+	                "3:\n\t"
+	                ".set   mips0\n\t"
+	                ".section .fixup,\"ax\"\n"
+	                "4:\n\t"
+	                "li     %2,%7\n\t"
+	                "j      3b\n\t"
+	                ".previous\n\t"
+	                ".section __ex_table,\"a\"\n\t"
+	                ".word  1b,4b\n\t"
+	                ".word  2b,4b\n\t"
+	                ".previous"
+	                : "=&r" (ret), "=R" (*ptr), "=r" (err), "=&r" (tmp)
+	                : "r" (val), "1" (*ptr), "2" (0), "i" (-EFAULT));
 #else
-	printk("sys_sysmips(MIPS_ATOMIC_SET, ...) not ready for !CONFIG_CPU_HAS_LLSC\n");
+		save_and_cli(tmp);
+		err = __get_user(ret, ptr);
+		if (ret != val)
+		err |= __put_user(val, ptr);    /* No fault
+                                                   unless unwriteable. */
+		restore_flags(tmp);
 #endif
+
+		if (err) {
+                        info.si_signo = SIGSEGV;
+			info.si_code = SEGV_MAPERR;
+			goto fault;
+		}
+			
+		if ( (ret < 0) && (ret >= -EMAXERRNO) ) {
+                        info.si_signo = SIGSYS;
+			info.si_code = 0;
+			goto fault;
+		}
+			
+		return ret;
+
+fault:
+		/* Go back to SYSCALL. */
+		((struct pt_regs *)&cmd)->cp0_epc -= 4;
+
+		info.si_addr = (void *)((struct pt_regs *)&cmd)->cp0_epc;
+		force_sig_info(info.si_signo, &info, current);
+
+		return 0;
 	}
 
 	case MIPS_FIXADE: