From 99590488e94b6b7f10ecf9a99398fd24a69a7039 Mon Sep 17 00:00:00 2001
From: Alexander Graf <agraf@suse.de>
Date: Wed, 2 Nov 2011 09:23:23 +0000
Subject: [PATCH] linux-user: add open() hijack infrastructure

There are a number of files in /proc that expose host information
to the guest program. This patch adds infrastructure to override
the open() syscall for guest programs to enable us to on the fly
generate guest sensible files.

Signed-off-by: Alexander Graf <agraf@suse.de>
---
 linux-user/syscall.c |   52 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 49 insertions(+), 3 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index f170724..1ecc0e1 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4603,6 +4603,52 @@ int get_osversion(void)
     return osversion;
 }
 
+static int do_open(void *cpu_env, const char *pathname, int flags, mode_t mode)
+{
+    struct fake_open {
+        const char *filename;
+        int (*fill)(void *cpu_env, int fd);
+    };
+    const struct fake_open *fake_open;
+    static const struct fake_open fakes[] = {
+        { NULL, NULL }
+    };
+
+    for (fake_open = fakes; fake_open->filename; fake_open++) {
+        if (!strncmp(pathname, fake_open->filename,
+                     strlen(fake_open->filename))) {
+            break;
+        }
+    }
+
+    if (fake_open->filename) {
+        const char *tmpdir;
+        char filename[PATH_MAX];
+        int fd, r;
+
+        /* create temporary file to map stat to */
+        tmpdir = getenv("TMPDIR");
+        if (!tmpdir)
+            tmpdir = "/tmp";
+        snprintf(filename, sizeof(filename), "%s/qemu-open.XXXXXX", tmpdir);
+        fd = mkstemp(filename);
+        if (fd < 0) {
+            return fd;
+        }
+        unlink(filename);
+
+        if ((r = fake_open->fill(cpu_env, fd))) {
+            close(fd);
+            return r;
+        }
+        lseek(fd, 0, SEEK_SET);
+
+        return fd;
+    }
+
+    return get_errno(open(path(pathname), flags, mode));
+}
+
 /* do_syscall() should always have a single exit point at the end so
    that actions, such as logging of syscall results, can be performed.
    All errnos that do_syscall() returns must be -TARGET_<errcode>. */
@@ -4688,9 +4734,9 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
     case TARGET_NR_open:
         if (!(p = lock_user_string(arg1)))
             goto efault;
-        ret = get_errno(open(path(p),
-                             target_to_host_bitmask(arg2, fcntl_flags_tbl),
-                             arg3));
+        ret = get_errno(do_open(cpu_env, p,
+                                target_to_host_bitmask(arg2, fcntl_flags_tbl),
+                                arg3));
         unlock_user(p, arg1, 0);
         break;
 #if defined(TARGET_NR_openat) && defined(__NR_openat)
-- 
1.6.0.2