| Message ID | 150912776103.20350.959452179379767829.malonedeb@soybean.canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | [Bug,1728116,NEW] Empty /proc/self/auxv (linux-user) | expand |
Oops, yes, commit 7c4ee5bcc82e643 broke this -- it switched the order in
which we fill in the AUXV info, but forgot to adjust the calculation of
the length, which as you've guessed we now get backwards.
** Changed in: qemu
Status: New => Confirmed
I've just sent this patch which fixes this bug:
https://lists.gnu.org/archive/html/qemu-devel/2017-11/msg01199.html
(it turns out it wasn't quite as simple as getting the sign wrong, we were subtracting two things that were totally wrong).
** Changed in: qemu
Status: Confirmed => In Progress
** Tags added: linux-user
Fix has been released with QEMU 2.11:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=f516511ea84d8bb3395d6e
** Changed in: qemu
Status: In Progress => Fix Released
diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 9b6364a..49285f9 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -7469,6 +7469,9 @@ static int open_self_auxv(void *cpu_env, int fd) abi_ulong len = ts->info->auxv_len; char *ptr; + gemu_log(TARGET_ABI_FMT_lu"\n", len); + gemu_log(TARGET_ABI_FMT_ld"\n", len); + /* * Auxiliary vector is stored in target process stack. * read in whole auxv vector and copy it to file
Public bug reported: The userspace Linux API virtualization used to fake access to /proc/self/auxv, to provide meaningful data for the guest process. For newer qemu versions, this fails: The openat() is intercepted, but there's no content: /proc/self/auxv has length zero (i.e. reading from it returns 0 bytes). Good: $ x86_64-linux-user/qemu-x86_64 /usr/bin/cat /proc/self/auxv | wc -c 256 /proc/self/auxv Bad: $ x86_64-linux-user/qemu-x86_64 /usr/bin/cat /proc/self/auxv | wc -c 0 /proc/self/auxv This worked in 2.7.1, and fails in 2.10.1. This causes e.g. any procps-ng-based tool to segfault while reading from /proc/self/auxv in an endless loop (probably worth another bug report...) Doing a "git bisect" shows that this commit: https://github.com/qemu/qemu/commit/7c4ee5bcc introduced the problem. It might be a simple logic (subtraction in the wrong direction?) or sign-ness error: Adding some logging (to v2.10.1) shows this output: $ x86_64-linux-user/qemu-x86_64 /usr/bin/cat /proc/self/auxv | wc -c 18446744073709551264 -352 0 And 352 could be the expected length. ** Affects: qemu Importance: Undecided Status: New