Messages in this thread | | | Date | Thu, 4 Feb 2016 14:39:07 +0000 | From | Russell King - ARM Linux <> | Subject | Re: linux-next: build failure after merge of the aio tree |
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On Thu, Feb 04, 2016 at 09:32:04AM -0500, Benjamin LaHaise wrote: > On Thu, Feb 04, 2016 at 02:12:53PM +0000, Russell King - ARM Linux wrote: > > Hence, __get_user() on x86-32 with a 64-bit quantity results in > > __get_user_bad() being called, which is an undefined function. > > Only if you build with x86-64 support enabled (iow, CONFIG_X86_32 not > > defined) then you get the 64-bit __get_user() support. > > > > Given this, I fail to see how x86-32 can possibly work. > > You're right; mea culpa. It compiles without warning on x86-32, but it > does not link. I still think this is broken archtecture stupidity since > put_user() works for 64 bit data types.
Indeed, and you'll find that several other architectures besides ARM and x86-32 have exactly the same problem - as I listed in my message from a few days ago.
Okay, so now I get to set you a challenge, since you're the one wanting 64-bit __get_user(): try implementing it on x86-32 :)
Also in my previous message from a few days ago I provided a set of functions which test out the implementation. Here they are... again.
All these should not produce any warnings, and should produce correct code - especially the narrowing/widening tests:
int test_8(unsigned char *v, unsigned char *p) { return __get_user(*v, p); } int test_8_constp(unsigned char *v, const unsigned char *p) { return __get_user(*v, p); } int test_8_volatilep(unsigned char *v, volatile unsigned char *p) { return __get_user(*v, p); } int test_16(unsigned short *v, unsigned short *p) { return __get_user(*v, p); } int test_16_constp(unsigned short *v, const unsigned short *p) { return __get_user(*v, p); } int test_32(unsigned int *v, unsigned int *p) { return __get_user(*v, p); } int test_32_constp(unsigned int *v, const unsigned int *p) { return __get_user(*v, p); } int test_64(unsigned long long *v, unsigned long long *p) { return __get_user(*v, p); } int test_64_constp(unsigned long long *v, const unsigned long long *p) { return __get_user(*v, p); } int test_ptr(unsigned int **v, unsigned int **p) { return __get_user(*v, p); } int test_const(unsigned int *v, const unsigned int *p) { return __get_user(*v, p); } int test_64_narrow(unsigned long *v, unsigned long long *p) { return __get_user(*v, p); } int test_32_wide(unsigned long long *v, unsigned long *p) { return __get_user(*v, p); }
However, this one should warn:
int test_wrong(char **v, const char **p) { return __get_user(*v, p); }
Good luck (I think you'll need lots of it to get a working solution)! :)
-- RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.
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