[PATCH] uml: skas0 stubs now check system call return values

Change syscall-stub's data to include a "expected retval".

Stub now checks syscalls retval and aborts execution of syscall list, if
retval != expected retval.

run_syscall_stub prints the data of the failed syscall, using the data pointer
and retval written by the stub to the beginning of the stack.

one_syscall_stub is removed, to simplify code, because only some instructions
are saved by one_syscall_stub, no host-syscall.

Using the stub with additional data (modify_ldt via stub)
is prepared also.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 138 insertions, 96 deletions

diff --git a/arch/um/kernel/skas/mem_user.c b/arch/um/kernel/skas/mem_user.c
index c976320ebe84..1d89640bd502 100644
--- a/arch/um/kernel/skas/mem_user.c
+++ b/arch/um/kernel/skas/mem_user.c
@@ -5,13 +5,14 @@
 
 #include <signal.h>
 #include <errno.h>
+#include <string.h>
 #include <sys/mman.h>
 #include <sys/wait.h>
 #include <asm/page.h>
 #include <asm/unistd.h>
 #include "mem_user.h"
 #include "mem.h"
-#include "mm_id.h"
+#include "skas.h"
 #include "user.h"
 #include "os.h"
 #include "proc_mm.h"
@@ -23,56 +24,99 @@
 #include "uml-config.h"
 #include "sysdep/ptrace.h"
 #include "sysdep/stub.h"
-#include "skas.h"
 
-extern unsigned long syscall_stub, batch_syscall_stub, __syscall_stub_start;
+extern unsigned long batch_syscall_stub, __syscall_stub_start;
 
 extern void wait_stub_done(int pid, int sig, char * fname);
 
+static inline unsigned long *check_init_stack(struct mm_id * mm_idp,
+					      unsigned long *stack)
+{
+	if(stack == NULL){
+		stack = (unsigned long *) mm_idp->stack + 2;
+		*stack = 0;
+	}
+	return stack;
+}
+
+extern int proc_mm;
+
 int single_count = 0;
+int multi_count = 0;
+int multi_op_count = 0;
 
-static long one_syscall_stub(struct mm_id * mm_idp, int syscall,
-			     unsigned long *args)
+static long do_syscall_stub(struct mm_id *mm_idp, void **addr)
 {
+	unsigned long regs[MAX_REG_NR];
+	unsigned long *data;
+	unsigned long *syscall;
+	long ret, offset;
         int n, pid = mm_idp->u.pid;
-        unsigned long regs[MAX_REG_NR];
+
+	if(proc_mm)
+#warning Need to look up userspace_pid by cpu
+		pid = userspace_pid[0];
+
+	multi_count++;
 
         get_safe_registers(regs);
         regs[REGS_IP_INDEX] = UML_CONFIG_STUB_CODE +
-                ((unsigned long) &syscall_stub -
+		((unsigned long) &batch_syscall_stub -
                  (unsigned long) &__syscall_stub_start);
-        /* XXX Don't have a define for starting a syscall */
-        regs[REGS_SYSCALL_NR] = syscall;
-        regs[REGS_SYSCALL_ARG1] = args[0];
-        regs[REGS_SYSCALL_ARG2] = args[1];
-        regs[REGS_SYSCALL_ARG3] = args[2];
-        regs[REGS_SYSCALL_ARG4] = args[3];
-        regs[REGS_SYSCALL_ARG5] = args[4];
-        regs[REGS_SYSCALL_ARG6] = args[5];
-        n = ptrace_setregs(pid, regs);
-        if(n < 0){
-		printk("one_syscall_stub : PTRACE_SETREGS failed, "
-		       "errno = %d\n", n);
-		return(n);
+	n = ptrace_setregs(pid, regs);
+	if(n < 0)
+		panic("do_syscall_stub : PTRACE_SETREGS failed, errno = %d\n",
+		      n);
+
+	wait_stub_done(pid, 0, "do_syscall_stub");
+
+	/* When the stub stops, we find the following values on the
+	 * beginning of the stack:
+	 * (long )return_value
+	 * (long )offset to failed sycall-data (0, if no error)
+	 */
+	ret = *((unsigned long *) mm_idp->stack);
+	offset = *((unsigned long *) mm_idp->stack + 1);
+	if (offset) {
+		data = (unsigned long *)(mm_idp->stack +
+					 offset - UML_CONFIG_STUB_DATA);
+		syscall = (unsigned long *)((unsigned long)data + data[0]);
+		printk("do_syscall_stub: syscall %ld failed, return value = "
+		       "0x%lx, expected return value = 0x%lx\n",
+		       syscall[0], ret, syscall[7]);
+		printk("    syscall parameters: "
+		       "0x%lx 0x%lx 0x%lx 0x%lx 0x%lx 0x%lx\n",
+		       syscall[1], syscall[2], syscall[3],
+		       syscall[4], syscall[5], syscall[6]);
+		for(n = 1; n < data[0]/sizeof(long); n++) {
+			if(n == 1)
+				printk("    additional syscall data:");
+			if(n % 4 == 1)
+				printk("\n      ");
+			printk("  0x%lx", data[n]);
+		}
+		if(n > 1)
+			printk("\n");
 	}
+	else ret = 0;
 
-	wait_stub_done(pid, 0, "one_syscall_stub");
+	*addr = check_init_stack(mm_idp, NULL);
 
-	return(*((unsigned long *) mm_idp->stack));
+	return ret;
 }
 
-int multi_count = 0;
-int multi_op_count = 0;
-
-static long many_syscall_stub(struct mm_id * mm_idp, int syscall,
-			      unsigned long *args, int done, void **addr_out)
+long run_syscall_stub(struct mm_id * mm_idp, int syscall,
+		      unsigned long *args, long expected, void **addr,
+ 		      int done)
 {
-        unsigned long regs[MAX_REG_NR], *stack;
-        int n, pid = mm_idp->u.pid;
+ 	unsigned long *stack = check_init_stack(mm_idp, *addr);
+
+	if(done && *addr == NULL)
+		single_count++;
+
+ 	*stack += sizeof(long);
+	stack += *stack / sizeof(long);
 
-        stack = *addr_out;
-        if(stack == NULL)
-                stack = (unsigned long *) current_stub_stack();
         *stack++ = syscall;
         *stack++ = args[0];
         *stack++ = args[1];
@@ -80,53 +124,55 @@ static long many_syscall_stub(struct mm_id * mm_idp, int syscall,
         *stack++ = args[3];
         *stack++ = args[4];
         *stack++ = args[5];
+	*stack++ = expected;
         *stack = 0;
         multi_op_count++;
 
         if(!done && ((((unsigned long) stack) & ~PAGE_MASK) <
-                     PAGE_SIZE - 8 * sizeof(long))){
-                *addr_out = stack;
+		     PAGE_SIZE - 10 * sizeof(long))){
+		*addr = stack;
                 return 0;
         }
 
-        multi_count++;
-        get_safe_registers(regs);
-        regs[REGS_IP_INDEX] = UML_CONFIG_STUB_CODE +
-                ((unsigned long) &batch_syscall_stub -
-                 (unsigned long) &__syscall_stub_start);
-        regs[REGS_SP_INDEX] = UML_CONFIG_STUB_DATA;
+	return do_syscall_stub(mm_idp, addr);
+}
 
-        n = ptrace_setregs(pid, regs);
-        if(n < 0){
-                printk("many_syscall_stub : PTRACE_SETREGS failed, "
-                       "errno = %d\n", n);
-                return(n);
-        }
+long syscall_stub_data(struct mm_id * mm_idp,
+		       unsigned long *data, int data_count,
+		       void **addr, void **stub_addr)
+{
+	unsigned long *stack;
+	int ret = 0;
+
+	/* If *addr still is uninitialized, it *must* contain NULL.
+	 * Thus in this case do_syscall_stub correctly won't be called.
+	 */
+	if((((unsigned long) *addr) & ~PAGE_MASK) >=
+	   PAGE_SIZE - (10 + data_count) * sizeof(long)) {
+		ret = do_syscall_stub(mm_idp, addr);
+ 		/* in case of error, don't overwrite data on stack */
+		if(ret)
+			return ret;
+	}
 
-        wait_stub_done(pid, 0, "many_syscall_stub");
-        stack = (unsigned long *) mm_idp->stack;
+	stack = check_init_stack(mm_idp, *addr);
+	*addr = stack;
 
-        *addr_out = stack;
-        return(*stack);
-}
+	*stack = data_count * sizeof(long);
 
-static long run_syscall_stub(struct mm_id * mm_idp, int syscall,
-                             unsigned long *args, void **addr, int done)
-{
-        long res;
+	memcpy(stack + 1, data, data_count * sizeof(long));
 
-        if((*addr == NULL) && done)
-                res = one_syscall_stub(mm_idp, syscall, args);
-        else res = many_syscall_stub(mm_idp, syscall, args, done, addr);
+	*stub_addr = (void *)(((unsigned long)(stack + 1) & ~PAGE_MASK) +
+			      UML_CONFIG_STUB_DATA);
 
-        return res;
+	return 0;
 }
 
-void *map(struct mm_id * mm_idp, unsigned long virt, unsigned long len,
-          int r, int w, int x, int phys_fd, unsigned long long offset,
-          int done, void *data)
+int map(struct mm_id * mm_idp, unsigned long virt, unsigned long len,
+	int r, int w, int x, int phys_fd, unsigned long long offset,
+	int done, void **data)
 {
-        int prot, n;
+        int prot, ret;
 
         prot = (r ? PROT_READ : 0) | (w ? PROT_WRITE : 0) |
                 (x ? PROT_EXEC : 0);
@@ -146,29 +192,27 @@ void *map(struct mm_id * mm_idp, unsigned long virt, unsigned long len,
                                                  .fd	= phys_fd,
                                                  .offset= offset
                                                } } } );
-                n = os_write_file(fd, &map, sizeof(map));
-                if(n != sizeof(map))
-                        printk("map : /proc/mm map failed, err = %d\n", -n);
+		ret = os_write_file(fd, &map, sizeof(map));
+		if(ret != sizeof(map))
+			printk("map : /proc/mm map failed, err = %d\n", -ret);
+		else ret = 0;
         }
         else {
-                long res;
                 unsigned long args[] = { virt, len, prot,
                                          MAP_SHARED | MAP_FIXED, phys_fd,
                                          MMAP_OFFSET(offset) };
 
-		res = run_syscall_stub(mm_idp, STUB_MMAP_NR, args,
-				       &data, done);
-                if((void *) res == MAP_FAILED)
-                        printk("mmap stub failed, errno = %d\n", res);
+		ret = run_syscall_stub(mm_idp, STUB_MMAP_NR, args, virt,
+				       data, done);
         }
 
-	return data;
+	return ret;
 }
 
-void *unmap(struct mm_id * mm_idp, void *addr, unsigned long len, int done,
-            void *data)
+int unmap(struct mm_id * mm_idp, void *addr, unsigned long len, int done,
+	  void **data)
 {
-        int n;
+        int ret;
 
         if(proc_mm){
                 struct proc_mm_op unmap;
@@ -180,29 +224,29 @@ void *unmap(struct mm_id * mm_idp, void *addr, unsigned long len, int done,
                                                  { .addr	=
                                                    (unsigned long) addr,
                                                    .len		= len } } } );
-                n = os_write_file(fd, &unmap, sizeof(unmap));
-		if(n != sizeof(unmap))
-		  printk("unmap - proc_mm write returned %d\n", n);
+		ret = os_write_file(fd, &unmap, sizeof(unmap));
+		if(ret != sizeof(unmap))
+			printk("unmap - proc_mm write returned %d\n", ret);
+		else ret = 0;
         }
         else {
-                int res;
                 unsigned long args[] = { (unsigned long) addr, len, 0, 0, 0,
                                          0 };
 
-		res = run_syscall_stub(mm_idp, __NR_munmap, args,
-				       &data, done);
-                if(res < 0)
-                        printk("munmap stub failed, errno = %d\n", res);
+		ret = run_syscall_stub(mm_idp, __NR_munmap, args, 0,
+				       data, done);
+                if(ret < 0)
+                        printk("munmap stub failed, errno = %d\n", ret);
         }
 
-        return data;
+        return ret;
 }
 
-void *protect(struct mm_id * mm_idp, unsigned long addr, unsigned long len,
-              int r, int w, int x, int done, void *data)
+int protect(struct mm_id * mm_idp, unsigned long addr, unsigned long len,
+	    int r, int w, int x, int done, void **data)
 {
         struct proc_mm_op protect;
-        int prot, n;
+        int prot, ret;
 
         prot = (r ? PROT_READ : 0) | (w ? PROT_WRITE : 0) |
                 (x ? PROT_EXEC : 0);
@@ -217,21 +261,19 @@ void *protect(struct mm_id * mm_idp, unsigned long addr, unsigned long len,
                                                      .len	= len,
                                                      .prot	= prot } } } );
 
-                n = os_write_file(fd, &protect, sizeof(protect));
-                if(n != sizeof(protect))
-                        panic("protect failed, err = %d", -n);
+                ret = os_write_file(fd, &protect, sizeof(protect));
+                if(ret != sizeof(protect))
+                        printk("protect failed, err = %d", -ret);
+                else ret = 0;
         }
         else {
-                int res;
                 unsigned long args[] = { addr, len, prot, 0, 0, 0 };
 
-                res = run_syscall_stub(mm_idp, __NR_mprotect, args,
-                                       &data, done);
-                if(res < 0)
-                        panic("mprotect stub failed, errno = %d\n", res);
+                ret = run_syscall_stub(mm_idp, __NR_mprotect, args, 0,
+                                       data, done);
         }
 
-        return data;
+        return ret;
 }
 
 void before_mem_skas(unsigned long unused)