int main(void) { uint8_t *p, *ep; size_t s = syslinux_adv_size(); char buf[256]; #if 0 /* this hangs! */ openconsole(&dev_stdcon_r, &dev_stdcon_w); #else /* this works */ openconsole(&dev_rawcon_r, &dev_ansiserial_w); #endif p = syslinux_adv_ptr(); printf("ADV size: %zd bytes at %p\n", s, p); ep = p + s; /* Need at least opcode+len */ while (p < ep - 1 && *p) { int t = *p++; int l = *p++; if (p + l > ep) break; memcpy(buf, p, l); buf[l] = '\0'; printf("ADV %3d: \"%s\"\n", t, buf); p += l; } return 0; }
int syslinux_setadv(int tag, size_t size, const void *data) { uint8_t *p, *advtmp; size_t rleft, left; if ((unsigned)tag - 1 > 254) { errno = EINVAL; return -1; /* Impossible tag value */ } if (size > 255) { errno = ENOSPC; /* Max 255 bytes for a data item */ return -1; } rleft = left = syslinux_adv_size(); p = advtmp = alloca(left); memcpy(p, syslinux_adv_ptr(), left); /* Make working copy */ while (rleft >= 2) { uint8_t ptag = p[0]; size_t plen = p[1] + 2; if (ptag == ADV_END) break; if (ptag == tag) { /* Found our tag. Delete it. */ if (plen >= rleft) { /* Entire remainder is our tag */ break; } memmove(p, p + plen, rleft - plen); rleft -= plen; /* Fewer bytes to read, but not to write */ } else { /* Not our tag */ if (plen > rleft) break; /* Corrupt tag (overrun) - overwrite it */ left -= plen; rleft -= plen; p += plen; } } /* Now (p, left) reflects the position to write in and how much space we have for our data. */ if (size) { if (left < size + 2) { errno = ENOSPC; /* Not enough space for data */ return -1; } *p++ = tag; *p++ = size; memcpy(p, data, size); p += size; left -= size + 2; } memset(p, 0, left); /* If we got here, everything went OK, commit the write to low memory */ memcpy(syslinux_adv_ptr(), advtmp, syslinux_adv_size()); return 0; }