How to resolve Segmentation Fault in RISC-V Program

[Vindhya Ejanthkar]

// factorial.c
#include <stdio.h>
unsigned long long factorial(unsigned int n) {
    if (n == 0)
        return 1;
    else
        return n * factorial(n - 1);
}
int main() {
    unsigned long long result = factorial(10);
    printf("Factorial of 10 = %llu\n", result);
    return 0;
}

1. Compiled the program using RISC-V GCC Compiler with optimization flags (-O2) and profiling flag (-pg).
2. Executed the compiled program using the Spike RISC-V simulator with pk.
3. Encountered a segfault error during execution.
   
   Attaching my commands and output :
   vindhya@latitude-7390:~$ nano factorial.c
   vindhya@latitude-7390:~$ /home/latitude-7390/rvv64/bin/riscv64-unknown-elf-gcc -O2 -pg factorial.c -o factorial
   vindhya@latitude-7390:~$ /home/vindhya/riscv-vector/riscv-isa-sim/build/spike /home/latitude-7390/rvv64/bin/riscv64-unknown-elf/bin/pk ./factorial
   z  0000000000000000 ra 00000000000101d4 sp 0000003fff7ffff0 gp 000000000001b018
   tp 0000000000000000 t0 0000000000010818 t1 000000000000000f t2 0000000000000000
   s0 0000000000000000 s1 0000000000000000 a0 00000000000101d4 a1 0000003ffffffb58
   a2 0000000000000000 a3 0000000000000010 a4 000000000001a680 a5 0000000000000000
   a6 000000000000001f a7 0000000000000000 s2 0000000000000000 s3 0000000000000000
   s4 0000000000000000 s5 0000000000000000 s6 0000000000000000 s7 0000000000000000
   s8 0000000000000000 s9 0000000000000000 sA 0000000000000000 sB 0000000000000000
   t3 0000000000000000 t4 0000000000000000 t5 0000000000000000 t6 0000000000000000
   pc 00000000000101cc va/inst 0000003fff7ffff8 sr 8000000200006020
   User store segfault @ 0x0000003fff7ffff8
   
   Let me know what more information should i provide and how to resolve this.
   

[Tommy Murphy]

You're compiling your program with a bare-metal Newlib toolchain (e.g. riscv64-unknown-elf-gcc) but running Spike with pk which is normally (always?) intended for programs compiled with the Linux toolchain (e.g. riscv64-unknown-linux-gnu-gcc) creating a Linux user mode executable.

You should search for information about running bare-metal programs on Spike. There should be some useful info out there for your situation. Or else try compiling your program with a RISC-V Linux toolchain.

[Bruce Hoult]

No, that's not correct. Newlib is simply a slimmer version of libc,
but still by default makes Linux syscalls for things such as printf.
It is absolutely normal to use riscv64-unknown-elf-gcc to make
programs to run in Spike because the most important attribute is it
links the program statically, so everything needed is included in the
one binary.

I use riscv64-unknown-elf-gcc all the time to make programs that I
want to run on a variety of RISC-V Linux boards with different OS
distros and different glibc versions.

On Tue, Mar 5, 2024 at 2:26 AM Tommy Murphy <tommy_...@hotmail.com> wrote:
>
> You're compiling your program with a bare-metal Newlib toolchain (e.g. riscv64-unknown-elf-gcc) but running Spike with pk which is normally (always?) intended for programs compiled with the Linux toolchain (e.g. riscv64-unknown-linux-gnu-gcc) creating a Linux user mode executable.
>
> You should search for information about running bare-metal programs on Spike. There should be some useful info out there for your situation. Or else try compiling your program with a RISC-V Linux toolchain.
>

> --
> You received this message because you are subscribed to the Google Groups "RISC-V SW Dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to sw-dev+un...@groups.riscv.org.
> To view this discussion on the web visit https://groups.google.com/a/groups.riscv.org/d/msgid/sw-dev/LO2P123MB7050F3AE610DEE51BD6386D2F9232%40LO2P123MB7050.GBRP123.PROD.OUTLOOK.COM.

[Vindhya Ejanthkar]

Any idea how to resolve this ?

[Tommy Murphy]

> No, that's not correct. 

Apologies if anything that I posted was inadvertently misleading. Thanks for correcting it, Bruce.

> Any idea how to resolve this ?

You should probably debug your program to identify the location and root cause of the crash first:

* https://github.com/riscv-software-src/riscv-isa-sim?tab=readme-ov-file#interactive-debug-mode

* https://github.com/riscv-software-src/riscv-isa-sim?tab=readme-ov-file#debugging-with-gdb