Please find submitted a patch for getdents (this system call stands for
"get directory entries", it is passed a file descriptor pointing to a
directory and returns a struct with info on the entries in that
directory.) This patch is against qemu-2.10 series but continues to apply
cleanly on current as of April 15 2018. If you are running a 32-bit binary
on 64-bit target current qemu will convert he getdents struct, but running
a 64-bit binary on 32-bit target it passes the struct straight through
causing incorrect behavior (file type is in the middle of the 64-bit struct
and at the end of the 32-bit one).
My use case for this has been running aapt (from Android SDK) and whatever
other misc x86-64 bins android studio runs when building on a 32-bit ARM (I
previously had run these x86-64 bins on 32-bit Intel). After an android
build tools update, aapt began erroring out until I applied this patch.
Peter Maydell has raised a concern about possible buffer overflows in this
code (which was meant to handle 32-bit app on 64-bit system, not 64-bit on
32-bit). I must admit I haven't gone through the dirent-copying code with
a fine-toothed comb... it appeared to work for my use case. That said, the
code seems to be careful about using offsetof() rather than making any
assumptions. In addition, the dirent-copying code appears to have an
assert that would crash qemu if it was going to write past the end of the
dirent buffer -- always nice to have plenty of sanity checks!
--Thanks!
Henry Wertz
Signed-off-by: Henry Wertz <hwert...@gmail.com>
*** linux-user/syscall.c~ 2017-03-04 10:31:14.000000000 -0600
--- linux-user/syscall.c 2017-03-07 17:08:24.615399116 -0600
***************
*** 9913,9921 ****
#endif
#ifdef TARGET_NR_getdents
case TARGET_NR_getdents:
#ifdef __NR_getdents
! #if TARGET_ABI_BITS == 32 && HOST_LONG_BITS == 64
{
struct target_dirent *target_dirp;
struct linux_dirent *dirp;
abi_long count = arg3;
--- 9913,9921 ----
#endif
#ifdef TARGET_NR_getdents
case TARGET_NR_getdents:
#ifdef __NR_getdents
! #if TARGET_ABI_BITS != HOST_LONG_BITS
{
struct target_dirent *target_dirp;
struct linux_dirent *dirp;
abi_long count = arg3;
