This patch give the possibility of time vdso support on 32bit kernel.
If the 32bit x86 kernel provides gettimeofday() and clock_gettime()
primitives in vdso. In this case make bionic use them. If the kernel
doesn't provide them, fallback to the legacy system call versions.
Change-Id: I87b772a9486fa356903e1f98f486ab9eb0b6f6f7
Signed-off-by: Robert Jarzmik <robert.jarzmik@intel.com>
Signed-off-by: Mingwei Shi <mingwei.shi@intel.com>
This reverts commit 1946856b1f.
This goes back to the original scheme of PROT_NONEing a page within
libc. Allocating a new page didn't fail safe for cases where these
functions are called from the dynamic linker.
Bug: http://b/22568628
Change-Id: I3e7241c8b54c27ea4a898bc952375c1e9ae38c80
Global, writable function pointers are low-hanging fruit for hijacking
control flow with an overflow from a global buffer or an arbitrary write
vulnerability. This moves the function pointer table into a dedicated
page and makes it read-only at runtime, similar to RELRO.
This increases the memory usage of the library by just under one page.
This could be avoided by having the linker load the vdso by replacing
weak symbols. It's not significant within the Zygote spawning model
though because it's read-only after early init.
Change-Id: Id7a49c96c1b15c2e1926528304b3c54a81e78caf
