On Fri, Feb 10, 2017 at 8:28 AM, Dmitry Safonov <dsafonov@xxxxxxxxxxxxx> wrote: > On 02/10/2017 07:13 PM, Andy Lutomirski wrote: >> >> On Fri, Feb 10, 2017 at 3:52 AM, Dmitry Safonov <dsafonov@xxxxxxxxxxxxx> >> wrote: >>> >>> Kernel erases R8..R11 registers prior returning to userspace >>> from int80: https://lkml.org/lkml/2009/10/1/164 >>> >>> GCC can reuse this registers and doesn't expect them to change >>> during syscall invocation. I met this kind of bug in CRIU once >>> gcc 6.1 and clang stored local variables in those registers >>> and the kernel zerofied them during syscall: >>> >>> https://github.com/xemul/criu/commit/990d33f1a1cdd17bca6c2eb059ab3be2564f7fa2 >>> >>> By that reason I suggest to add those registers to clobbers >>> in selftests. >> >> >> Seems reasonable, but presumably INT80_CLOBBERS should be defined the >> same way in all the tests. IOW, if the "flags" clobber is actually >> needed, it should be "flags", INT80_CLOBBERS (possibly without the >> comma if it's problematic). >> > > Well, that was my initial attempt: I've defined it as: > +# define INT80_CLOBBERS , "r8", "r9", "r10", "r11" > > But that hanging comma looks awful, so I added "flags" there. > And if I do define it without coma and leave it in asm statement, > 32-bit version would be unhappy. > So, I found that it's easier to define it with flags included. > Woudl the right answer be to get rid of "flags" in the test where it appears? I'm not sure it's needed in the first place. -- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
