[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, 34 insertions, 8 deletions

diff --git a/arch/um/sys-i386/stub.S b/arch/um/sys-i386/stub.S
index a0f9506312d1..6a70d9ab5c29 100644
--- a/arch/um/sys-i386/stub.S
+++ b/arch/um/sys-i386/stub.S
@@ -2,24 +2,50 @@
 
         .globl syscall_stub
 .section .__syscall_stub, "x"
-syscall_stub:
-        int     $0x80
-        mov     %eax, UML_CONFIG_STUB_DATA
-        int3
 
         .globl batch_syscall_stub
 batch_syscall_stub:
-        mov     $UML_CONFIG_STUB_DATA, %esp
-again:  pop     %eax
+        /* load pointer to first operation */
+        mov     $(UML_CONFIG_STUB_DATA+8), %esp
+
+again:
+        /* load length of additional data */
+        mov     0x0(%esp), %eax
+
+        /* if(length == 0) : end of list */
+        /* write possible 0 to header */
+        mov     %eax, UML_CONFIG_STUB_DATA+4
         cmpl    $0, %eax
         jz      done
+
+        /* save current pointer */
+        mov     %esp, UML_CONFIG_STUB_DATA+4
+
+        /* skip additional data */
+        add     %eax, %esp
+
+        /* load syscall-# */
+        pop     %eax
+
+        /* load syscall params */
         pop     %ebx
         pop     %ecx
         pop     %edx
         pop     %esi
         pop     %edi
         pop     %ebp
+
+        /* execute syscall */
         int     $0x80
+
+        /* check return value */
+        pop     %ebx
+        cmp     %ebx, %eax
+        je      again
+
+done:
+        /* save return value */
         mov     %eax, UML_CONFIG_STUB_DATA
-        jmp     again
-done:   int3
+
+        /* stop */
+        int3