On Tue, Aug 18, 2015 at 10:25:31AM +0000, Nikola Veljkovic wrote: > There is a discrepancy in the personality() syscall on mips64. > > For a 32bit process (o32 or n32) sys_32_personality() [1] is called, which > converts PER_LINUX32 -> PER_LINUX: > > ret = sys_personality(p); > if (ret != -1 && (ret & PER_MASK) == PER_LINUX32) // personality macro applied > ret = (ret & ~PER_MASK) | PER_LINUX; // to make it clearer > > This is different than what Intel and ARM are doing. They directly invoke > sys_personality(). On Android, this causes a bionic test to fail for mips, as it > expects PER_LINUX32 but receives PER_LINUX, when ran on mips64 core. > > The code itself comes from older kernel versions (2.4), where it was also used > by other architectures [2], [3], [4]. However, since kernel 2.6 other archs are > invoking sys_personality() directly, for all ABIs. > > Is there any reason why we should do PER_LINUX32 -> PER_LINUX on mips? Also, if > we do change this for o32, should we change it for n32, as well? There is no n32 > support for Android, so it would have to be tested elsewhere. > > Tested changing only o32 on Android, there were no regressions: > > diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S > index ab93427..b94ee4e 100644 > --- a/arch/mips/kernel/scall64-o32.S > +++ b/arch/mips/kernel/scall64-o32.S > @@ -358,7 +358,7 @@ sys_call_table: > sys sys_fchdir 1 > sys sys_bdflush 2 > sys sys_sysfs 3 /* 4135 */ > - sys sys_32_personality 1 > + sys sys_personality 1 > sys sys_ni_syscall 0 /* for afs_syscall */ > sys sys_setfsuid 1 > sys sys_setfsgid 1 > -- > > [1] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/mips/kernel/linux32.c#n122 > [2] http://git.linux-mips.org/cgit/ralf/linux.git/tree/include/asm-mips64/elf.h?h=linux-2.4#n124 > [3] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/x86_64/ia32/sys_ia32.c?h=linux-2.4#n1974 > [4] http://git.linux-mips.org/cgit/ralf/linux.git/tree/arch/ia64/ia32/sys_ia32.c?h=linux-2.4#n4005 > -- > Nikola Veljkovic Hi, I am not sure what the implication will be to userland with that change... I presume you also need to fix the n32 case and then completely remove the sys_32_personality syscall from linux32.c. Moreover, I think you also need to fix the arch/mips/include/asm/elf.h code to set LINUX32 for O32 and n32 (for both 32b and 64b kernels.) If you are going to submit a new patch, can you please create a proper git patch (using git format-patch) and include your Signed-off-by line as well? Thank you -- markos
