[Buildroot] [PATCH] toolchain: generate check-headers program under $(BUILD_DIR)

[Carlos Santos]

On Mon, Sep 23, 2019 at 5:39 AM <yann.morin at orange.com> wrote:
>
> Carlos, All,
>
> On 2019-09-22 22:05 -0300, unixmania at gmail.com spake thusly:
> > From: Carlos Santos <unixmania at gmail.com>
> >
> > Some installations mount /tmp with the 'noexec' option, which prevents
> > running the program generated there to check the kernel headers.
>
> I'm rather surprised that check-headers is the nly thing broken in that
> case... :-/
>
> Alternatively, we should probably use our own TMPDIR instead, which
> would fix all such problems:
>
>     diff --git a/Makefile b/Makefile
>     index 82c844620a..a006149898 100644
>     --- a/Makefile
>     +++ b/Makefile
>     @@ -209,6 +209,11 @@ BASE_TARGET_DIR := $(BASE_DIR)/target
>      HOST_DIR := $(BASE_DIR)/host
>      GRAPHS_DIR := $(BASE_DIR)/graphs
>
>     +export TMPDIR = $(BUILD_DIR)/.br-temp-or-whatever
>     +export TMP_DIR = $(TMPDIR)
>     +export TEMP_DIR = $(TMPDIR)
>     +# And so on...

That would create all temporary files under
$(BUILD_DIR)/.br-temp-or-whatever, ruining the advantage of using a
tmpfs mounted at /tmp, which is much faster because it's in RAM.

>      LEGAL_INFO_DIR = $(BASE_DIR)/legal-info
>      REDIST_SOURCES_DIR_TARGET = $(LEGAL_INFO_DIR)/sources
>      REDIST_SOURCES_DIR_HOST = $(LEGAL_INFO_DIR)/host-sources
>     @@ -1016,7 +1021,7 @@ savedefconfig: $(BUILD_DIR)/buildroot-config/conf outputmakefile
>
>      # staging and target directories do NOT list these as
>      # dependencies anywhere else
>     -$(BUILD_DIR) $(BASE_TARGET_DIR) $(HOST_DIR) $(BINARIES_DIR) $(LEGAL_INFO_DIR) $(REDIST_SOURCES_DIR_TARGET) $(REDIST_SOURCES_DIR_HOST):
>     +$(BUILD_DIR) $(BASE_TARGET_DIR) $(HOST_DIR) $(BINARIES_DIR) $(LEGAL_INFO_DIR) $(REDIST_SOURCES_DIR_TARGET) $(REDIST_SOURCES_DIR_HOST) $(TMPDIR):
>         @mkdir -p $@
>
>      # outputmakefile generates a Makefile in the output directory, if using a
>
> Doing smething like that would solve the issue globally, rather than
> having ad-hoc solutions everywhere this will be needed.
>
> > Avoid the problem by generating the program under $(BUILD_DIR), passed
> > as the first argument to check-kernel-headers.sh.
> >
> > Fixes: https://bugs.busybox.net/show_bug.cgi?id=12241
> [--SNIP--]
> > diff --git a/support/scripts/check-kernel-headers.sh b/support/scripts/check-kernel-headers.sh
> > index a8cca78b27..cbf71e0f23 100755
> > --- a/support/scripts/check-kernel-headers.sh
> > +++ b/support/scripts/check-kernel-headers.sh
> > @@ -1,14 +1,17 @@
> >  #!/bin/sh
> >
> > -SYSROOT="${1}"
> > +BUILDDIR="${1}"
> > +SYSROOT="${2}"
> >  # Make sure we have enough version components
> > -HDR_VER="${2}.0.0"
> > +HDR_VER="${3}.0.0"
> >
> >  HDR_M="${HDR_VER%%.*}"
> >  HDR_V="${HDR_VER#*.}"
> >  HDR_m="${HDR_V%%.*}"
> >
> > -EXEC="$(mktemp -t check-headers.XXXXXX)"
> > +EXEC="$(mktemp -p "${BUILDDIR}" -t .check-headers.XXXXXX)"
> > +
> > +trap 'rm -f "${EXEC}"' EXIT
>
> Two things:
>
> 1. A trap on EXIT is a bashism, while this script uses /bin/sh, which
> is not guaranteed to be bash.

>From the IEEE Std 1003.1, 2004 Edition
(https://pubs.opengroup.org/onlinepubs/009695399/utilities/trap.html):

"The condition can be EXIT, 0 (equivalent to EXIT), or a signal
specified using a symbolic name, without the SIG prefix [...]"

> 2. Why do you want to use a trap on EXIT? If there is a motivation to do
> so, it does not seem to be related to this change anyway, so should be
> done in its own patch.

It's a cleaner solution.

-- 
Carlos Santos <unixmania at gmail.com>