pmeerw's blog

Sun, 16 Jun 2019

Assembler at your fingertips: rappel

rappel is a Linux-based assembly REPL (read-eval-print loop) supporting Intel syntax. Quite handy to try out various instructions:

rax: 0x0000000000000001	rbx: 0x0000000000000002	rcx: 0x0000000000000000	rdx: 0x0000000000000000
rsi: 0x0000000000000000	rdi: 0x0000000000000000	r8 : 0x0000000000000000	r9 : 0x0000000000000000
r10: 0x0000000000000000	r11: 0x0000000000000000	r12: 0x0000000000000000	r13: 0x0000000000000000
r14: 0x0000000000000000	r15: 0x0000000000000000
rip: 0x0000000000400006	rsp: 0x00007fffd64d8f10	rbp: 0x0000000000000000
flags: 0x0000000000000202 [cf:0, zf:0, of:0, sf:0, pf:0, af:0, df:0]
> add eax,ebx
rax: 0x0000000000000003	rbx: 0x0000000000000002	rcx: 0x0000000000000000	rdx: 0x0000000000000000
rsi: 0x0000000000000000	rdi: 0x0000000000000000	r8 : 0x0000000000000000	r9 : 0x0000000000000000
r10: 0x0000000000000000	r11: 0x0000000000000000	r12: 0x0000000000000000	r13: 0x0000000000000000
r14: 0x0000000000000000	r15: 0x0000000000000000
rip: 0x0000000000400003	rsp: 0x00007fffd64d8f10	rbp: 0x0000000000000000
flags: 0x0000000000000206 [cf:0, zf:0, of:0, sf:0, pf:1, af:0, df:0]

Under the hood, it just runs nasm and observes register values. FP/XMM is supported as well...

posted at: 23:00 | path: /programming | permanent link

Wed, 12 Jun 2019

Ubuntu 19.04, two monitor setup

Using two 27" monitors now: one Iiyama (3840x2160), one BenQ (1920x1080). The first has way higher DPI. To compensate, I use fractional scaling (175% and 100%). This needs to be enabled for X11, requires Ubuntu 19.04:

gsettings set org.gnome.mutter experimental-features "['x11-randr-fractional-scaling']"
See here for more details.

posted at: 21:28 | path: /configuration | permanent link

Mon, 20 May 2019

Debugging a WWAN USB stick

What to do when a USB WWAN (UMTS) stick doesn't work? That is, network manager shown broadband as not enabled...

The kernel log looks good:

[ 3313.057520] usb 2-1: New USB device found, idVendor=0e8d, idProduct=00a5, bcdDevice= 3.00
[ 3313.057528] usb 2-1: New USB device strings: Mfr=9, Product=10, SerialNumber=0
[ 3313.057536] usb 2-1: Manufacturer: MediaTek Inc
[ 3313.085587] cdc_mbim 2-1:1.0: cdc-wdm0: USB WDM device
[ 3313.086142] cdc_mbim 2-1:1.0 wwan0: register 'cdc_mbim' at usb-0000:00:14.0-1, CDC MBIM, d2:9c:37:32:10:73
[ 3313.086885] option 2-1:1.2: GSM modem (1-port) converter detected
[ 3313.087140] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB0
[ 3313.087520] option 2-1:1.3: GSM modem (1-port) converter detected
[ 3313.087654] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB1
[ 3313.087924] option 2-1:1.4: GSM modem (1-port) converter detected
[ 3313.088050] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB2
[ 3313.088322] option 2-1:1.5: GSM modem (1-port) converter detected
[ 3313.090237] usb 2-1: GSM modem (1-port) converter now attached to ttyUSB3
[ 3313.090693] usb-storage 2-1:1.6: USB Mass Storage device detected
[ 3313.143856] cdc_mbim 2-1:1.0 wwp0s20u1: renamed from wwan0
[ 3314.109400] scsi 3:0:0:0: Direct-Access     MEDIATEK  FLASH DISK      6225 PQ: 0 ANSI: 0 CCS
[ 3314.110360] sd 3:0:0:0: Attached scsi generic sg1 type 0
[ 3314.128902] sd 3:0:0:0: [sdb] 0 512-byte logical blocks: (0 B/0 B)
[ 3314.131013] sd 3:0:0:0: [sdb] Attached SCSI removable disk
The ModemManager has a useful command-line tool, mmcli, that can be used to show status of the modem. Try mmcli -v -m 6 where 6 is an index of the modem:
[20 Mai 2019, 18:56:55] [Debug] ModemManager process found at ':1.2'
[20 Mai 2019, 18:56:55] [Debug] Assuming '6' is the modem index
[20 Mai 2019, 18:56:55] [Debug] Modem found at '/org/freedesktop/ModemManager1/Modem/6'

[20 Mai 2019, 18:56:55] [Debug] Printing modem info...
  --------------------------
  General  |      dbus path: /org/freedesktop/ModemManager1/Modem/6
           |      device id: a67f08189ddc6295ad23160780ebeb06a0925a6c
  --------------------------
  Hardware |   manufacturer: MediaTek Inc
           |          model: Product
           |       revision: UW980_42M_ESMT_V101R01B08
           |   h/w revision: MTK2
           |      supported: gsm-umts
           |        current: gsm-umts
           |   equipment id: 355128006541593
  --------------------------
  System   |         device: /sys/devices/pci0000:00/0000:00:14.0/usb2/2-1
           |        drivers: cdc_mbim, option1
           |         plugin: Generic
           |   primary port: cdc-wdm0
           |          ports: ttyUSB0 (at), ttyUSB1 (at), cdc-wdm0 (mbim), wwp0s20u1 (net)
  --------------------------
  Status   |          state: failed
           |  failed reason: sim-missing
           |    power state: on
           | signal quality: 0% (cached)
  --------------------------
  Modes    |      supported: allowed: 2g, 3g; preferred: none
           |        current: allowed: any; preferred: none
  --------------------------
  IP       |      supported: ipv4, ipv6, ipv4v6
In this case, the SIM card seem to be missing (failed reason: sim-missing); or defective rather.

posted at: 21:26 | path: /configuration | permanent link

Sat, 18 May 2019

New PC build: Ryzen 5 2400G

I got a AMD Ryzen 5 2400G, Asus X370-A Prime mainboard, a pair of G.Skill F4-3000C16D (Aegis) 8 GB DDR4 RAM modules, a AData XPG SX8200 512 GB NVMe SSD (M.2-2280), be quiet Pure Power 11 400W power supply, all in a Chieftec Elox HC-10b case.

So far, so good; RAM is working at 3000MHz, CPU slightly overclocked at 3750 MHz.

The particular mainboard has two PCI slots (hard to find these days :-), and can take up to 4 RAM modules (max. 64 GB).

posted at: 19:03 | path: /review | permanent link

Thu, 16 May 2019

Epson ET-2710

Epson has a line of EcoTank inkjet printers which promises to bring the ink cost down thanks to ink tanks that can be poured into the printer, no ink cardridges. The printer is about 230 € (May 2019).

It is a multi-function device, i.e. printer/scanner/copier, with several limitations: no fax, no duplex, no automatic document feeder, no card reader. Higher priced models add these features. The printer does WiFi and WiFi Direct -- installation is a bit cumbersome due to the lack of a display.

Linux support is acceptable, Epson provides PPD files which integrate nicely with lsb, but does not support those files. Hard to find: http://download.ebz.epson.net/dsc/search/01/search/?OSC=LX Tested with Ubuntu 18.04.

The scanner part is also supported, I've so far tested the network support (should also work over USB): http://support.epson.net/linux/en/imagescanv3.php. Tested with Ubuntu 19.04.

posted at: 17:05 | path: /review | permanent link

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