See what takes time in kernel compilation

Makefile projects can be profiled and debugged with the remake project. You need a recent version of remake that supports --profile=json (see --help).

This works with parallel builds as well (I've use -j8 here but use whatever you have).

• "name" is the makefile target
• "len" is the duration in seconds

$ cd linux-git
$ mkdir -p json && remake --profile=json --profile-directory=$PWD/json -j8
$ cd json
 

# Look at items sorted by total time (time taken by all dependencies + the recipe length)
$ jq -s '[.[] |.targets[]|select(.recipe!=null)|{ name: .name, len: (.end-.start) }]|sort_by(-.len)' *.json
[
  {
    "name": "bzImage",
    "len": 77.26787257194519
  },
  {
    "name": "vmlinux",
    "len": 76.33200693130493
  },
  {
    "name": "arch/x86/kernel/vmlinux.lds",
    "len": 75.16884279251099
  },
  {
    "name": "drivers",
    "len": 75.013343334198
  },
  {
    "name": "arch/x86/lib/lib.a",
    "len": 75.01327657699585
  },
....

# Or look at item sorted by recipe time only (without the dependencies)
$ jq -s '[.[] |.targets[]|select(.recipe!=null)|{ name: .name, len: (.end-.recipe) }]|sort_by(-.len)' *json
[
  {
    "name": "drivers",
    "len": 47.737035512924194
  },
  {
    "name": "fs",
    "len": 45.02375769615173
  },
  {
    "name": "net",
    "len": 40.28609848022461
  },
  {
    "name": "net/ipv4",
    "len": 31.197179794311523
  },
...

AdressSanitizer link error and autoconf configure script

If you get linking errors like the following when trying to use AddressSanitizer in an autoconf project:

spnego.c:(.text+0x3c): undefined reference to `__asan_option_detect_stack_use_after_return'
/bin/ld: spnego.c:(.text+0x49): undefined reference to `__asan_stack_malloc_1'
/bin/ld: spnego.c:(.text+0xfd): undefined reference to `__asan_report_load16'
/bin/ld: spnego.c:(.text+0x180): undefined reference to `__asan_report_load8'
/bin/ld: spnego.c:(.text+0x1ad): undefined reference to `__asan_report_load8'
/bin/ld: spnego.c:(.text+0x1ff): undefined reference to `__asan_report_load8'
/bin/ld: spnego.c:(.text+0x22e): undefined reference to `__asan_report_load8'

It's because the configure guesses something wrong. You can work around it by providing the answer via an env var like so:

CFLAGS='-fsanitize=address' \
LDFLAGS='-fsanitize=address' \
ac_cv_func_malloc_0_nonnull=yes \
./configure

notmuch mark as spam

Adds a keybinding that applies/removes tags to the currently viewed email or --when looking at search results-- the thread under point.

(defun mark-spam ()
  (interactive)
  (let ((tlist '("+spam" "-unread" "-inbox" "-new")))
    (if (eq major-mode 'notmuch-show-mode)
 (progn
   (let ((id (notmuch-show-get-message-id)))
     (notmuch-tag id tlist)
     (notmuch-show-next-thread)))
      (notmuch-search-tag tlist)
      (notmuch-search-next-thread))))

(define-key 'notmuch-search-mode-map (kbd "S") 'mark-spam)
(define-key 'notmuch-show-mode-map (kbd "S") 'mark-spam)

_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build

_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build

If you are pulling your hair and wondering why your kernel does not have a /sys/kernel/debug/dynamic_debug directory despite having CONFIG_DYNAMIC_DEBUG enabled and debugfs mounted, the issue could be that you built the kernel using GOLD linker. You can simply switch through the LD Makefile variable (make LD=ld.bfd)

Extracting and applying a clean git patchset from an email thread with notmuch

I just wrote a quick python script to filter the actual patches from a email thread send with git send-email (those "[PATCH 1/15] xyz" threads). The script assumes you use notmuch. Give it a search expression that returns a list of messages that includes all the patches like the thread-id (C-u c i while looking at the thread in emacs).

You can get it on github. There is a small elisp snippet in the README to run the script and apply the patchset from emacs.

Copy current buffer absolute file path to the OS clipboard

(defun copy-full-path ()
  (interactive)
  (let ((path (buffer-file-name)))
    (when path
      (setq path (expand-file-name path))
      (funcall interprogram-cut-function path)
      (message "copied %s in clipboard" path))))

Quick-and-dirty email template for notmuch

(defun prepare-report ()
  (interactive)
  (notmuch-mua-new-mail)
  (insert "foo@example.com")
  (search-forward "Subject: ")
  (insert "work report week " (format-time-string "%W"))
  (search-forward "\n\n")
  (backward-char)
  (insert "my super email content\n"))