In the Proxy Kernel, gettimeofday always returns 0

[forresti]

I'm building a simple program with riscv-gcc and running with the proxy kernel. I'm using the proxy kernel to obtain some system libraries such as time.h.

Here's an example usage:

struct timeval tp;
struct timezone tzp;
gettimeofday(&tp,&tzp);
printf("time = %f \n", (double)tp.tv_sec + (double)tp.tv_usec*1.e-6); 

This always prints 0.0000, even when called in a long loop. Strange...

Any ideas what might be going wrong?

I can provide code and give more details if anyone wants to try to reproduce it.

Thanks,
Forrest

[ccelio]

Well, if we disassemble that code we get this:

00000000000187d8 <gettimeofday>:
  187d8:   00093423    sd zero,8(a0)
  187dc:   00093023    sd zero,0(a0)
  187e0:   00000813    li v0,0
  187e4:   0000806f    ret

So yah, it's only ever going to return zero. "gettimeofday" should make a syscall, which would be handled by the riscv-pk (SYS_time) properly and return a value based off of "rdcycle()" and assuming a 1GHz clock.

So the question is why is the compiler giving us the wrong code, when the proxy-kernel is waiting for a SYS_time syscall? I'm guessing a stub somewhere in riscv-gcc didn't get filled out, but I don't really know where to look myself.

[aswaterman]

Newlib's implementation of gettimeofday was doing exactly what Chris'
disassembly would suggest. I've changed it to use rdtime, assuming a
timebase of 1 GHz, which is on the right order of magnitude, at least.

Need to rebuild riscv-gcc before rebuilding riscv-pk.

On Tue, Nov 12, 2013 at 10:54 PM, Christopher Celio <
notifications@github.com> wrote:

Well, if we disassemble that code we get this:

00000000000187d8 :
187d8: 00093423 sd zero,8(a0)
187dc: 00093023 sd zero,0(a0)
187e0: 00000813 li v0,0
187e4: 0000806f ret

So yah, it's only ever going to return zero. "gettimeofday" should make a
syscall, which would be handled by the riscv-pk (SYS_time) properly and
return a value based off of "rdcycle()" and assuming a 1GHz clock.

So the question is why is the compiler giving us the wrong code, when the
proxy-kernel is waiting for a SYS_time syscall?

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