Re: randconfig build error with next-20150529, in crypto/jitterentropy.c

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On 06/08/2015 03:36 PM, Stephan Mueller wrote:
Am Monday 08 June 2015, 12:54:12 schrieb Guenter Roeck:

Hi Guenter,

Thanks for the note.

...

---

openrisc:defconfig:

In file included from ./arch/openrisc/include/asm/timex.h:23:0,
	...
	from crypto/jitterentropy.c:52:
./arch/openrisc/include/asm/spr.h: In function 'jent_loop_shuffle':
./arch/openrisc/include/asm/spr.h:30:2: warning: asm operand 1 probably
doesn't match constraints
./arch/openrisc/include/asm/spr.h:30:2: error: impossible constraint in 'asm'

I received this one also before. But that seems to be an error on the OpenRISC
platform as the random_get_entropy() function or the get_cycles function is
not implemented as defined.

The crypto code uses the following which triggers the issue:

         __u64 tmp = 0;

         tmp = random_get_entropy();

That one seems to be an appropriate use of random_get_entropy() which on
almost all arches is an alias for get_cycles().

Yes and no. I suspect it may have something to do with the compiler options.
The code compiles with the following patch applied.

---
diff --git a/arch/openrisc/include/asm/spr.h b/arch/openrisc/include/asm/spr.h
index 1cccb42dd477..373532cc41f4 100644
--- a/arch/openrisc/include/asm/spr.h
+++ b/arch/openrisc/include/asm/spr.h
@@ -24,7 +24,7 @@
        "l.mtspr %0,%1,%2"                                      \
        : : "r" (_off), "r" (_val), "K" (_spr))

-static inline unsigned long mfspr(unsigned long add)
+static inline unsigned long mfspr(const unsigned long add)
 {
        unsigned long ret;
        __asm__ __volatile__ ("l.mfspr %0,r0,%1" : "=r" (ret) : "K" (add));

---

get_cycles is implemented as static inline which executes mfspr(SPR_TTCR).
SPR_TTCR is a constant. Normally that information seems to be passed on,
but not when get_cycles() is compiled through jitterentropy.

Any idea what might cause this ?

Thanks,
Guenter

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