[PATCH] i386 ptrace patch needed for user-mode port

Jeff Dike (jdike@karaya.com)
Sun, 26 Sep 1999 15:49:21 -0400

Below is a small patch to ptrace which enables it to change system call
numbers. This is needed in order to run the user-mode port.

It adds range checks to ptrace and to the slow system call path.

I've been feeding this sporadically to Linus for the last couple of months
with no result. If anyone can clue me in as to what would make this more
acceptable, please do so.

Jeff

diff -Naur -X ../exclude-files orig/arch/i386/kernel/entry.S
um/arch/i386/kernel/entry.S
--- orig/arch/i386/kernel/entry.S Sat Sep 25 10:09:14 1999
+++ um/arch/i386/kernel/entry.S Sat Sep 25 10:10:03 1999
@@ -237,9 +237,11 @@
movl $-ENOSYS,EAX(%esp)
call SYMBOL_NAME(syscall_trace)
movl ORIG_EAX(%esp),%eax
+ cmpl $(NR_syscalls),%eax
+ jae 1f
call *SYMBOL_NAME(sys_call_table)(,%eax,4)
movl %eax,EAX(%esp) # save the return value
- call SYMBOL_NAME(syscall_trace)
+1: call SYMBOL_NAME(syscall_trace)
jmp ret_from_sys_call
badsys:
movl $-ENOSYS,EAX(%esp)
diff -Naur -X ../exclude-files orig/arch/i386/kernel/ptrace.c
um/arch/i386/kernel/ptrace.c
--- orig/arch/i386/kernel/ptrace.c Sat Aug 7 22:46:11 1999
+++ um/arch/i386/kernel/ptrace.c Tue Aug 3 13:43:42 1999
@@ -73,7 +73,9 @@
{
switch (regno >> 2) {
case ORIG_EAX:
- return -EIO;
+ if (value >= NR_syscalls)
+ return -EIO;
+ break;
case FS:
if (value && (value & 3) != 3)
return -EIO;

-
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