FreeBSD Mail Archives

Date:      Wed, 22 Aug 2007 23:10:47 +0200
From:      Roman Divacky <rdivacky@freebsd.org>
To:        Yuriy Tsibizov <yuriy.tsibizov@gmail.com>
Cc:        freebsd-hackers@freebsd.org, freebsd-emulation@freebsd.org
Subject:   Re: User-mode Linux (Was: modify syscall nr on-the-fly)
Message-ID:  <20070822211047.GA35783@freebsd.org>
In-Reply-To: <c019b3090708220242s690b673i601899c0be2b32d4@mail.gmail.com>
References:  <c019b3090708211153o7dce8365l945b24ad1c962d22@mail.gmail.com> <c019b3090708220242s690b673i601899c0be2b32d4@mail.gmail.com>

here is a little review of mine... just little suggestions.

Index: i386/i386/trap.c
===================================================================
RCS file: /home/ncvs/src/sys/i386/i386/trap.c,v
retrieving revision 1.307
diff -u -r1.307 trap.c
--- i386/i386/trap.c	26 Jul 2007 15:32:55 -0000	1.307
+++ i386/i386/trap.c	22 Aug 2007 08:53:19 -0000
@@ -1004,6 +1004,32 @@
 
 		PTRACESTOP_SC(p, td, S_PT_SCE);
 
+		if (__predict_false(p->p_sysent->sv_name[0]=='L')) {

please use __predict_true(p->p_sysent != &elf_linux_sysvec)

+			if (code != frame->tf_eax) {
+			printf("linux sysctl patched: code %d return eax %d\n", code, frame->tf_eax);
+				/* retry */
+				code = frame->tf_eax;
+			
+				if (p->p_sysent->sv_prepsyscall)
+					/*
+					 * The prep code is MP aware.
+					 */
+					(*p->p_sysent->sv_prepsyscall)(frame, args, &code, &params);
+				/* else should always be null */
+
+			 	if (p->p_sysent->sv_mask)
+			 		code &= p->p_sysent->sv_mask;

the sv_mask should be removed.. dont use it in your code. its entirely pointless when dealing
with Linux binaries

+			 	if (code >= p->p_sysent->sv_size)
+			 		callp = &p->p_sysent->sv_table[0];
+			  	else
+			 		callp = &p->p_sysent->sv_table[code];
+
+				narg = callp->sy_narg;
+				/* retry ends */
+			}
+		}
+
 		AUDIT_SYSCALL_ENTER(code, td);
 		error = (*callp->sy_call)(td, args);
 		AUDIT_SYSCALL_EXIT(error, td);
Index: i386/linux/linux_ptrace.c
===================================================================
RCS file: /home/ncvs/src/sys/i386/linux/linux_ptrace.c,v
retrieving revision 1.17
diff -u -r1.17 linux_ptrace.c
--- i386/linux/linux_ptrace.c	22 Feb 2006 18:57:49 -0000	1.17
+++ i386/linux/linux_ptrace.c	22 Aug 2007 09:27:01 -0000
@@ -78,6 +78,7 @@
 #define PTRACE_SETFPXREGS	19
 
 #define PTRACE_SETOPTIONS	21
+#define PTRACE_O_TRACESYSGOOD	0x00000001
 
 /*
  * Linux keeps debug registers at the following
@@ -95,6 +96,10 @@
 	return ((signum == SIGSTOP)? 0 : signum);
 }
 
+struct linux_pt_lreg {
+	l_long reg[19];
+};
+
 struct linux_pt_reg {
 	l_long	ebx;
 	l_long	ecx;
@@ -103,17 +108,17 @@
 	l_long	edi;
 	l_long	ebp;
 	l_long	eax;
-	l_int	xds;
-	l_int	xes;
-	l_int	xfs;
-	l_int	xgs;
+	l_long	xds;
+	l_long	xes;
+	l_long	xfs;
+	l_long	xgs;
 	l_long	orig_eax;
 	l_long	eip;
-	l_int	xcs;
+	l_long	xcs;
 	l_long	eflags;
 	l_long	esp;
-	l_int	xss;
-};
+	l_long	xss;
+} __packed;

why is this necessary? how does it affect amd64 linux32 emulator?
 
 /*
  *   Translate i386 ptrace registers between Linux and FreeBSD formats.
@@ -247,6 +252,7 @@
 		struct linux_pt_reg	reg;
 		struct linux_pt_fpreg	fpreg;
 		struct linux_pt_fpxreg	fpxreg;
+		struct linux_pt_lreg	lreg;
 	} r;
 	union {
 		struct reg		bsd_reg;
@@ -429,20 +435,21 @@
 		 * as necessary.
 		 */
 		if (uap->addr < sizeof(struct linux_pt_reg)) {
+			if (uap->addr == (11 << 2)) /* orig_eax */
+				uap->addr = (6 << 2); /* eax */
+			
 			error = kern_ptrace(td, PT_GETREGS, pid, &u.bsd_reg, 0);
 			if (error != 0)
 				break;
 
 			map_regs_to_linux(&u.bsd_reg, &r.reg);
 			if (req == PTRACE_PEEKUSR) {
-				error = copyout((char *)&r.reg + uap->addr,
-				    (void *)uap->data, sizeof(l_int));
+				error = copyout((l_long*)(&r.lreg.reg[uap->addr>>2]),
+				    (void *)uap->data, sizeof(l_long));
 				break;
 			}
 
-			*(l_int *)((char *)&r.reg + uap->addr) =
-			    (l_int)uap->data;
-
+			r.lreg.reg[uap->addr>>2] = (l_long)uap->data;
 			map_regs_from_linux(&u.bsd_reg, &r.reg);
 			error = kern_ptrace(td, PT_SETREGS, pid, &u.bsd_reg, 0);
 		}
@@ -470,11 +477,34 @@
 			error = kern_ptrace(td, PT_SETDBREGS, pid,
 			    &u.bsd_dbreg, 0);
 		}
-
+	}
+		break;
+	case PTRACE_SETOPTIONS: {
+		struct proc *p;
+		if (uap->data == PTRACE_O_TRACESYSGOOD) {
+			p = td->td_proc;
+			PROC_LOCK(p);
+			p->p_stops |= S_PT_SYSGOOD;
+			PROC_UNLOCK(p);
+			break;
+		}
+		printf("linux: ptrace(21,...,%u) not implemented\n",
+		    (unsigned int)uap->data);
+		error = EINVAL;
+		}
 		break;

braces around case "case" ? please remove (the blocking there is implicit) and introduce
procedure-wide "p"

+	case PTRACE_SYSCALL: {
+		struct proc *p;
+
+		p = td->td_proc;
+		PROC_LOCK(p);
+		p->p_stops |= S_PT_LINUX;
+		PROC_UNLOCK(p);
+
+		if (addr == NULL) addr = (void *)1;
+		error = kern_ptrace(td, PT_SYSCALL, pid, addr, uap->data);
 	}
-	case PTRACE_SYSCALL:
-		/* fall through */
+		break;

ditto.

 	default:
 		printf("linux: ptrace(%u, ...) not implemented\n",
 		    (unsigned int)uap->req);
Index: sys/cdefs.h
===================================================================
RCS file: /home/ncvs/src/sys/sys/cdefs.h,v
retrieving revision 1.93
diff -u -r1.93 cdefs.h
--- sys/cdefs.h	21 Sep 2006 01:38:58 -0000	1.93
+++ sys/cdefs.h	10 Aug 2007 18:01:34 -0000
@@ -338,6 +338,10 @@
 #endif
 
 /* Compiler-dependent macros that rely on FreeBSD-specific extensions. */
+#ifndef __FreeBSD_cc_version
+#define __FreeBSD_cc_version 0
+#endif
+
 #if __FreeBSD_cc_version >= 300001 && defined(__GNUC__) && !defined(__INTEL_COMPILER)
 #define	__printf0like(fmtarg, firstvararg) \
 	    __attribute__((__format__ (__printf0__, fmtarg, firstvararg)))
Index: sys/ptrace.h
===================================================================
RCS file: /home/ncvs/src/sys/sys/ptrace.h,v
retrieving revision 1.28
diff -u -r1.28 ptrace.h
--- sys/ptrace.h	6 Feb 2006 09:41:56 -0000	1.28
+++ sys/ptrace.h	22 Aug 2007 08:53:45 -0000
@@ -103,7 +103,12 @@
 #define	PTRACESTOP_SC(p, td, flag)				\
 	if ((p)->p_flag & P_TRACED && (p)->p_stops & (flag)) {	\
 		PROC_LOCK(p);					\
-		ptracestop((td), SIGTRAP);			\
+		if (__predict_false(p->p_sysent->sv_name[0]=='L')) { \

please use p->p_sysent instead like stated above

+			(p)->p_stops &= ~(S_PT_SCE | S_PT_SCX);	\
+			ptracestop((td), SIGTRAP | 0x80); 	\
+			}					\
+		else						\
+			ptracestop((td), SIGTRAP);		\
 		PROC_UNLOCK(p);					\
 	}
 /*
@@ -112,6 +117,16 @@
  */
 #define	S_PT_SCE	0x000010000
 #define	S_PT_SCX	0x000020000
+/* 
+ * Linux ptrace conventions: clear S_PT_SCE and S_PT_SCX before raising
+ * signals
+ */
+#define S_PT_LINUX	0x000040000
+/* 
+ * Linux ptrace option PTRACE_O_TRACESYSGOOD, when enabled, changes signal
+ * number to ( SIGTRAP | 0x80 )
+ */
+#define S_PT_SYSGOOD	0x000080000
 
 int	ptrace_set_pc(struct thread *_td, unsigned long _addr);
 int	ptrace_single_step(struct thread *_td);
Index: compat/linux/linux_misc.c
===================================================================
RCS file: /home/ncvs/src/sys/compat/linux/linux_misc.c,v
retrieving revision 1.213
diff -u -r1.213 linux_misc.c
--- compat/linux/linux_misc.c	12 Jun 2007 00:11:57 -0000	1.213
+++ compat/linux/linux_misc.c	22 Aug 2007 09:07:34 -0000
@@ -63,6 +63,7 @@
 #include <sys/vmmeter.h>
 #include <sys/vnode.h>
 #include <sys/wait.h>
+#include <sys/ptrace.h>
 
 #include <security/mac/mac_framework.h>
 
@@ -852,6 +853,8 @@
 
 	if (args->status) {
 		tmpstat &= 0xffff;
+		if (!(td->td_proc->p_stops & S_PT_SYSGOOD))
+			tmpstat &= 0x7fff;
 		if (WIFSIGNALED(tmpstat))
 			tmpstat = (tmpstat & 0xffffff80) |
 			    BSD_TO_LINUX_SIGNAL(WTERMSIG(tmpstat));
@@ -898,6 +901,8 @@
 
 	if (args->status) {
 		tmpstat &= 0xffff;
+		if (!(td->td_proc->p_stops & S_PT_SYSGOOD))
+			tmpstat &= 0x7fff;
 		if (WIFSIGNALED(tmpstat))
 			tmpstat = (tmpstat & 0xffffff80) |
 			    BSD_TO_LINUX_SIGNAL(WTERMSIG(tmpstat));


thnx for the patch!

roman

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