Restore user-owned bits from PSW after a signal handler, instead of

copying complete PSW after signal handler.

This fixes a psw corruption bug reported by Jens de Smit <jst260@few.vu.nl>.

diff --git a/include/ibm/cpu.h b/include/ibm/cpu.h
index 691ca11db8c690ee9fb8220171a61496e73ab688..ff885b32c58d4739a89478dfb5a2495cb3b1907e 100755 (executable)
--- a/include/ibm/cpu.h
+++ b/include/ibm/cpu.h
@@ -1,15 +1,19 @@
 #ifndef _IBM_CPU_H
 #define _IBM_CPU_H 1
 
-#define X86_FLAG_C     (1L << 0)       /* Carry */
-#define X86_FLAG_P     (1L << 2)       /* Parity */
-#define X86_FLAG_A     (1L << 4)       /* Aux. carry */
-#define X86_FLAG_Z     (1L << 6)       /* Zero */
-#define X86_FLAG_S     (1L << 7)       /* Sign */
-
-#define X86_FLAG_T     (1L <<  8)      /* Trap */
-#define X86_FLAG_I     (1L <<  9)      /* Interrupt */
-#define X86_FLAG_D     (1L << 10)      /* Direction */
-#define X86_FLAG_O     (1L << 11)      /* Overflow */
+#define X86_FLAG_C     (1L << 0)       /* S  Carry */
+#define X86_FLAG_P     (1L << 2)       /* S  Parity */
+#define X86_FLAG_A     (1L << 4)       /* S  Aux. carry */
+#define X86_FLAG_Z     (1L << 6)       /* S  Zero */
+#define X86_FLAG_S     (1L << 7)       /* S  Sign */
+
+#define X86_FLAG_T     (1L <<  8)      /* X  Trap */
+#define X86_FLAG_I     (1L <<  9)      /* X  Interrupt */
+#define X86_FLAG_D     (1L << 10)      /* C  Direction */
+#define X86_FLAG_O     (1L << 11)      /* S  Overflow */
+
+/* User flags are S (Status) and C (Control) flags. */
+#define X86_FLAGS_USER (X86_FLAG_C | X86_FLAG_P | X86_FLAG_A | X86_FLAG_Z | \
+       X86_FLAG_S | X86_FLAG_D | X86_FLAG_O)
 
 #endif

diff --git a/kernel/system/do_sigreturn.c b/kernel/system/do_sigreturn.c
index 97a99c34a2eb4693ab321748984c8d24f1a93587..894260d44c95cd615faeab68874dc3018a81df1d 100644 (file)
--- a/kernel/system/do_sigreturn.c
+++ b/kernel/system/do_sigreturn.c
@@ -10,6 +10,7 @@
 #include "../system.h"
 #include <string.h>
 #include <signal.h>
+#include <ibm/cpu.h>
 #include <sys/sigcontext.h>
 
 #if USE_SIGRETURN 
@@ -38,7 +39,9 @@ message *m_ptr;                       /* pointer to request message */
   if (src_phys == 0) return(EFAULT);
   phys_copy(src_phys, vir2phys(&sc), (phys_bytes) sizeof(struct sigcontext));
 
-  sc.sc_psw  = rp->p_reg.psw;
+  /* Restore user bits of psw from sc, maintain system bits from proc. */
+  sc.sc_psw  =  (sc.sc_psw & X86_FLAGS_USER) |
+                (rp->p_reg.psw & ~X86_FLAGS_USER);
 
 #if (_MINIX_CHIP == _CHIP_INTEL)
   /* Don't panic kernel if user gave bad selectors. */