Le 29/08/2018 à 11:23, Shivaprasad G Bhat a écrit : > If the hostpage size is greater than the TARGET_PAGESIZE, the > target-pages of size TARGET_PAGESIZE are marked valid only till the > length requested during the elfload. The glibc attempts to consume unused > space in the last page of data segment(__libc_memalign() in > elf/dl-minimal.c). If PT_LOAD p_align is greater than or > equal to hostpage size, the GLRO(dl_pagesize) is actually the host pagesize > as set in the auxillary vectors. So, there is no explicit mmap request for > the remaining target-pages on the last hostpage. The glibc assumes that > particular space as available and subsequent attempts to use > those addresses lead to crash as the target_mmap has not marked them valid > for those target-pages. > > The issue is seen when trying to chroot to 16.04-x86_64 ubuntu on a PPC64 > host where the fork fails to access the thread_id as it is allocated on a > page not marked valid. The recent glibc doesn't have checks for thread-id in > fork, but the issue can manifest somewhere else, none the less. > > The fix here is to map all the target-pages of the hostpage during the > elfload if the p_align is greater than or equal to hostpage size, for > data segment to allow the glibc for proper consumption. > > Signed-off-by: Shivaprasad G Bhat <sb...@linux.vnet.ibm.com> > --- > v2: https://lists.gnu.org/archive/html/qemu-devel/2018-08/msg05943.html > Changes from v2: > - Simplified the macro as suggested. > - Fixed some grammatical error in commit message. > v1: https://lists.gnu.org/archive/html/qemu-devel/2018-08/msg05730.html > Changes from v1: > - Made the conditionals consistent with the commit "33143c446e" and > changed the commit message accordingly. > > linux-user/elfload.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) >
Reviewed-by: Laurent Vivier <laur...@vivier.eu>
