On Wed, Sep 22, 2021 at 10:46 AM Richard Palethorpe rpalethorpe@suse.de wrote:
Richard Palethorpe rpalethorpe@suse.de writes:
Then the output is:
[ 11.252268] io_pgetevents(f7f19000, 4294967295, 1, ...) [ 11.252401] comparing 4294967295 <= 1 io_pgetevents02.c:114: TPASS: invalid min_nr: io_pgetevents() failed as expected: EINVAL (22) [ 11.252610] io_pgetevents(f7f19000, 1, 4294967295, ...) [ 11.252748] comparing 1 <= 4294967295 io_pgetevents02.c:103: TFAIL: invalid max_nr: io_pgetevents() passed unexpectedly
and below is the macro expansion for the automatically generated 32bit to 64bit io_pgetevents. I believe it is casting u32 to s64, which appears to mean there is no sign extension. I don't know if this is the expected behaviour?
Thank you for digging through this, I meant to already reply once more yesterday but didn't get around to that.
__typeof(__builtin_choose_expr( (__builtin_types_compatible_p(typeof((long)0), typeof(0LL)) || __builtin_types_compatible_p(typeof((long)0), typeof(0ULL))), 0LL, 0L)) min_nr, __typeof(__builtin_choose_expr( (__builtin_types_compatible_p(typeof((long)0), typeof(0LL)) || __builtin_types_compatible_p(typeof((long)0), typeof(0ULL))), 0LL, 0L)) nr,
The part that I remembered is in arch/s390/include/asm/syscall_wrapper.h, which uses this version instead:
#define __SC_COMPAT_CAST(t, a) \ ({ \ long __ReS = a; \ \ BUILD_BUG_ON((sizeof(t) > 4) && !__TYPE_IS_L(t) && \ !__TYPE_IS_UL(t) && !__TYPE_IS_PTR(t) && \ !__TYPE_IS_LL(t)); \ if (__TYPE_IS_L(t)) \ __ReS = (s32)a; \ if (__TYPE_IS_UL(t)) \ __ReS = (u32)a; \ if (__TYPE_IS_PTR(t)) \ __ReS = a & 0x7fffffff; \ if (__TYPE_IS_LL(t)) \ return -ENOSYS; \ (t)__ReS; \ })
This also takes care of s390-specific pointer conversion, which is the reason for needing an architecture-specific wrapper, but I suppose the handling of signed arguments as done in s390 should also be done everywhere else.
I also noticed that only x86 and s390 even have separate entry points for normal syscalls when called in compat mode, while the others all just zero the upper halves of the registers in the low-level entry code and then call the native entry point.
Arnd