PTRACE_GETSIGINFO si_code for breakpoint doesn't match with siginfo.h definition

Question

I'm using PTRACE_GETSIGINFO to get information over the nature of a SIGTRAP signal. I want to know if the SIGTRAP was triggered by a software breakpoint, a hardware breakpoint, a fork... However, the si_code field from siginfo_t is set to 0x80 when hitting a breakpoint, where it should be 1 looking at header asm/siginfo.h. Do you have any idea of where this value is defined ? I made a small program to reproduce the issue :

#include <sys/ptrace.h>
#include <unistd.h>
#include <stdint.h>
#include <stdio.h>
#include <sys/user.h>
#include <signal.h>

int main() {
    pid_t pid;
    if(!(pid = fork())) {
        ptrace(PTRACE_TRACEME, NULL, NULL, NULL);
        __asm__("int3");
        return 0;
    }
    ptrace(PTRACE_ATTACH, pid, NULL, NULL);
    struct user_regs_struct regs;
    waitpid(pid, NULL, NULL);
    ptrace(PTRACE_CONT, pid, NULL, NULL);
    waitpid(pid, NULL, NULL);
    ptrace(PTRACE_GETREGS, pid, NULL, &regs);
    regs.rip--;
    uint64_t read_word = ptrace(PTRACE_PEEKDATA, pid, regs.rip, NULL);
    printf("Read byte : %x\n", read_word & 0xff);
    siginfo_t si;
    ptrace(PTRACE_GETSIGINFO, pid, 0, &si);
    printf("Signal : %llx\n", si.si_signo);
    printf("Code : %llx\n", si.si_code);
    return 0;
}

And the output is :

Read byte : cc
Signal : 5
Code : 80