QEMU_STRACE documentation bit by Thayne Harbaugh.

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@3822 c046a42c-6fe2-441c-8c8c-71466251a162

linux-user/main.c

@@ -1906,7 +1906,12 @@ void usage(void)
            "debug options:\n"
            "-d options   activate log (logfile=%s)\n"
            "-p pagesize  set the host page size to 'pagesize'\n"
-           "-strace      log system calls\n",
+           "-strace      log system calls\n"
+           "\n"
+           "environment variables:\n"
+           "QEMU_STRACE       Print system calls and arguments similar to the\n"
+           "                  'strace' program.  Enable by setting to any value.\n"
+           ,
            TARGET_ARCH,
            interp_prefix,
            x86_stack_size,

qemu-doc.texi

@@ -2507,6 +2507,17 @@ Activate log (logfile=/tmp/qemu.log)
 Act as if the host page size was 'pagesize' bytes
 @end table
 
+Environment variables:
+
+@table @env
+@item QEMU_STRACE
+Print system calls and arguments similar to the 'strace' program
+(NOTE: the actual 'strace' program will not work because the user
+space emulator hasn't implemented ptrace).  At the moment this is
+incomplete.  All system calls that don't have a specific argument
+format are printed with information for six arguments.  Many
+flag-style arguments don't have decoders and will show up as numbers.
+
 @node Other binaries
 @subsection Other binaries