[03/19] linux-user: add open() hijack infrastructure

Submitted by riku.voipio@linaro.org on Jan. 31, 2012, 9:29 a.m.

Details

Message ID ca6956285b4ba6a9c66e705e86ebe062d5ac0b00.1328001769.git.riku.voipio@linaro.org
State New
Headers show

Commit Message

riku.voipio@linaro.org Jan. 31, 2012, 9:29 a.m.
From: Alexander Graf <agraf@suse.de>

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>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
---
 linux-user/syscall.c |   52 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 49 insertions(+), 3 deletions(-)

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diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 2bf9e7e..e100025 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4600,6 +4600,52 @@  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>. */
@@ -4685,9 +4731,9 @@  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)