Hi Muhammad On Mon, Aug 19, 2024 at 3:05 AM Muhammad Usama Anjum <Usama.Anjum@xxxxxxxxxxxxx> wrote: > > On 8/14/24 3:29 AM, Jeff Xu wrote: > > Hi Muhammad > > > > On Fri, Aug 9, 2024 at 1:25 AM Muhammad Usama Anjum > > <usama.anjum@xxxxxxxxxxxxx> wrote: > >> > >> The __NR_mmap isn't found on armhf. The mmap() is commonly available > >> system call and its wrapper is presnet on all architectures. So it > >> should be used directly. It solves problem for armhf and doesn't create > >> problem for architectures as well. Remove sys_mmap() functions as they > >> aren't doing anything else other than calling mmap(). There is no need > >> to set errno = 0 manually as glibc always resets it. > >> > > The mseal_test should't have dependency on libc, and mmap() is > > implemented by glibc, right ? > > > > I just fixed a bug to switch mremap() to sys_mremap to address an > > issue that different glibc version's behavior is slightly different > > for mremap(). > > > > What is the reason that __NR_mmap not available in armhf ? (maybe it > > is another name ?) there must be a way to call syscall directly on > > armhf, can we use that instead ? > > It seems __NR_mmap syscall is deprecated for arm. Found this comment in > arch/arm/include/asm/unistd.h: > /* > * The following syscalls are obsolete and no longer available for EABI: > * __NR_time > * __NR_umount > * __NR_stime > * __NR_alarm > * __NR_utime > * __NR_getrlimit > * __NR_select > * __NR_readdir > * __NR_mmap > * __NR_socketcall > * __NR_syscall > * __NR_ipc > */ > > The glibc mmap() calls mmap2() these days by adjusting the parameters > internally. From man mmap: > C library/kernel differences: > This page describes the interface provided by the glibc mmap() wrapper > function. Originally, this function invoked a system call of the same > name. Since Linux 2.4, that system call has been superseded by > mmap2(2), and nowadays the glibc mmap() wrapper function invokes > mmap2(2) with a suitably adjusted value for offset. > > I'm not sure if behaviour of glibc mmap() and syscall mmap2() would be > same, but we should use glibc at most places which accounts for > different architectures correctly. Maybe the differences were only > present in case of mremap(). > We shouldn't use glibc to test mseal, mseal is a security feature, and an attacker can access syscall directly, so the test needs to test with as little layer as possible. I think there are two options: 1> switch everything to use __NR_mmap2 2> switch to __NR_mmap2 only for ARM. I'm not sure which one is more appropriate though. Thanks -Jeff > -- > BR, > Muhammad Usama Anjum >
