From: Ben Gras <ben@minix3.org>
Date: Tue, 8 May 2007 15:43:00 +0000 (+0000)
Subject: Restore user-owned bits from PSW after a signal handler, instead of
X-Git-Tag: v3.1.4~381
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/style.css?a=commitdiff_plain;h=b00f2874490fcf135807c3510206697f8bb7aa6a;p=minix.git

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 691ca11db..ff885b32c 100755
--- 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 97a99c34a..894260d44 100644
--- 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. */