From: Hiltjo Posthuma [hil...@codemadness.org]
Sent: Wednesday, September 6, 2017 5:32 PM
To: hackers mail list
Subject: Re: [hackers] [dwm][PATCH] move config data to read-only sections
On Wed, Sep 06, 2017 at 05:07:06PM +0200, Anselm R Garbe wrote:
> Hi Joachim,
>
> On 6 September 2017 at 17:02, <joachim.he...@t-systems.com> wrote:
> > commit 6a5056d4c919bb5ae0222b2fde0ed787d50092cf
> > Author: Joachim Henke <joachim.he...@t-systems.com>
> > AuthorDate: Wed, 6 Sep 2017 16:26:42 +0200
> >
> > The configuration data is just used read-only. So making it immutable
> > might improve security. Testing on x86_64 showed that the .data section
> > shrunk considerably: by ~2500 bytes.
> >
> > diff --git a/config.def.h b/config.def.h
> > index a9ac303..a43a03c 100644
> > --- a/config.def.h
> > +++ b/config.def.h
> > @@ -5,14 +5,14 @@ static const unsigned int borderpx = 1; /* border
> > pixel of windows */
> > static const unsigned int snap = 32; /* snap pixel */
> > static const int showbar = 1; /* 0 means no bar */
> > static const int topbar = 1; /* 0 means bottom bar */
> > -static const char *fonts[] = { "monospace:size=10" };
> > +static const char *const fonts[] = { "monospace:size=10" };
> > static const char dmenufont[] = "monospace:size=10";
> > static const char col_gray1[] = "#222222";
> > static const char col_gray2[] = "#444444";
> > static const char col_gray3[] = "#bbbbbb";
> > static const char col_gray4[] = "#eeeeee";
> > static const char col_cyan[] = "#005577";
> > -static const char *colors[][3] = {
> > +static const char *const colors[][3] = {
> > /* fg bg border */
> > [SchemeNorm] = { col_gray3, col_gray1, col_gray2 },
> > [SchemeSel] = { col_gray4, col_cyan, col_cyan },
> > @@ -56,10 +56,10 @@ static const Layout layouts[] = {
> >
> > /* commands */
> > static char dmenumon[2] = "0"; /* component of dmenucmd, manipulated in
> > spawn() */
> > -static const char *dmenucmd[] = { "dmenu_run", "-m", dmenumon, "-fn",
> > dmenufont, "-nb", col_gray1, "-nf", col_gray3, "-sb", col_cyan, "-sf",
> > col_gray4, NULL };
> > -static const char *termcmd[] = { "st", NULL };
> > +static const char *const dmenucmd[] = { "dmenu_run", "-m", dmenumon,
> > "-fn", dmenufont, "-nb", col_gray1, "-nf", col_gray3, "-sb", col_cyan,
> > "-sf", col_gray4, NULL };
> > +static const char *const termcmd[] = { "st", NULL };
> >
> > -static Key keys[] = {
> > +static const Key keys[] = {
> > /* modifier key function argument
> > */
> > { MODKEY, XK_p, spawn, {.v =
> > dmenucmd } },
> > { MODKEY|ShiftMask, XK_Return, spawn, {.v =
> > termcmd } },
> > @@ -98,7 +98,7 @@ static Key keys[] = {
> >
> > /* button definitions */
> > /* click can be ClkLtSymbol, ClkStatusText, ClkWinTitle, ClkClientWin, or
> > ClkRootWin */
> > -static Button buttons[] = {
> > +static const Button buttons[] = {
> > /* click event mask button function
> > argument */
> > { ClkLtSymbol, 0, Button1, setlayout,
> > {0} },
> > { ClkLtSymbol, 0, Button3, setlayout,
> > {.v = &layouts[2]} },
> > diff --git a/drw.c b/drw.c
> > index 319eb6b..902976f 100644
> > --- a/drw.c
> > +++ b/drw.c
> > @@ -153,7 +153,7 @@ xfont_free(Fnt *font)
> > }
> >
> > Fnt*
> > -drw_fontset_create(Drw* drw, const char *fonts[], size_t fontcount)
> > +drw_fontset_create(Drw* drw, const char *const fonts[], size_t fontcount)
> > {
> > Fnt *cur, *ret = NULL;
> > size_t i;
> > @@ -194,7 +194,7 @@ drw_clr_create(Drw *drw, XftColor *dest, const char
> > *clrname)
> > /* Wrapper to create color schemes. The caller has to call free(3) on the
> > * returned color scheme when done using it. */
> > Scm
> > -drw_scm_create(Drw *drw, const char *clrnames[], size_t clrcount)
> > +drw_scm_create(Drw *drw, const char *const clrnames[], size_t clrcount)
> > {
> > size_t i;
> > Scm ret;
> > diff --git a/drw.h b/drw.h
> > index ff4355b..2de6a6f 100644
> > --- a/drw.h
> > +++ b/drw.h
> > @@ -32,14 +32,14 @@ void drw_resize(Drw *drw, unsigned int w, unsigned int
> > h);
> > void drw_free(Drw *drw);
> >
> > /* Fnt abstraction */
> > -Fnt *drw_fontset_create(Drw* drw, const char *fonts[], size_t fontcount);
> > +Fnt *drw_fontset_create(Drw* drw, const char *const fonts[], size_t
> > fontcount);
> > void drw_fontset_free(Fnt* set);
> > unsigned int drw_fontset_getwidth(Drw *drw, const char *text);
> > void drw_font_getexts(Fnt *font, const char *text, unsigned int len,
> > unsigned int *w, unsigned int *h);
> >
> > /* Colorscheme abstraction */
> > void drw_clr_create(Drw *drw, XftColor *dest, const char *clrname);
> > -Scm drw_scm_create(Drw *drw, const char *clrnames[], size_t clrcount);
> > +Scm drw_scm_create(Drw *drw, const char *const clrnames[], size_t
> > clrcount);
> >
> > /* Cursor abstraction */
> > Cur *drw_cur_create(Drw *drw, int shape);
>
> I like your patch, at first glance it makes config.h more consistent
> with the other const declarations, however I need to browse through
> the patches if there were any places, where the non-const declaration
> was on purpose for some reason prior to accepting this upstream.
>
> BR,
> Anselm
Please no const char *const. I'm ok with the other const changes though.
--
Kind regards,
Hiltjo
Well, C might not have the most beautiful syntax in this regard, but I see no
other way to make a pointer itself read-only (and especially the ...cmd[]
pointer arrays really should be). Would using a typedef for that be more
comfortable to you?
Regards,
Jo.
