Re: [Buildroot] [PATCH 1/1] package: busybox: backport fix for missing getrandom()

["Yann E. MORIN" <yann.morin.1998@free.fr>]

Raphaël, All,

On 2023-04-19 14:51 +0200, Raphaël Mélotte spake thusly:
> The current Busybox version (1.36.0) fails to build with some
> libc/linux combinations where getrandom() is not available. Two fixes
> for glibc already exists upstream, so backport them here. A third
> one (submitted upstream, not part of the main branch yet) was needed
> to be able to compile with older musl and uClibc versions (or older
> kernels).
> 
> This fixes the following build failure raised since commit
> d68b617993bd2f5c82a4936ed1e24e4fec6b94a2:
> 
> miscutils/seedrng.c:45:24: fatal error: sys/random.h: No such file or directory
>  #include <sys/random.h>
> 
> Fixes:
> - http://autobuild.buildroot.net/results/44a0476b86c579e6aa658f156f0292958d40513c
> - http://autobuild.buildroot.net/results/ed028160db397581558fd8c96755621dd8298bb1
> - https://gitlab.com/buildroot.org/buildroot/-/jobs/4122624008
> - https://gitlab.com/buildroot.org/buildroot/-/jobs/4122624034
> - https://gitlab.com/buildroot.org/buildroot/-/jobs/4122624044
> - https://gitlab.com/buildroot.org/buildroot/-/jobs/4122624048
> - https://gitlab.com/buildroot.org/buildroot/-/jobs/4122624051
> 
> It also fixes the following (similar) build failure, raised since the
> same commit:
> 
> miscutils/lib.a(seedrng.o): In function `seedrng_main':
> seedrng.c:(.text.seedrng_main+0x26c): undefined reference to `getrandom'
> seedrng.c:(.text.seedrng_main+0x2e8): undefined reference to `getrandom'
> collect2: error: ld returned 1 exit status
> 
> Fixes:
> - https://gitlab.com/buildroot.org/buildroot/-/jobs/4122624028
> - https://gitlab.com/buildroot.org/buildroot/-/jobs/4122624031
> 
> Signed-off-by: Raphaël Mélotte <raphael.melotte@mind.be>

I had to backport this patch, as it causes build failures:

    $ cat defconfig
    BR2_arm=y
    BR2_cortex_a7=y
    BR2_TOOLCHAIN_EXTERNAL=y
    BR2_TOOLCHAIN_EXTERNAL_BOOTLIN=y

    $ make busybox-configure
    [...]
    ..../build/busybox-1.36.0/Makefile.flags:165: *** unterminated call to function 'shell': missing ')'.  Stop.


... which is dues to some issue in (scroll down)...

> diff --git a/package/busybox/0007-seedrng-fix-getrandom-detection-for-non-glibc-libc.patch b/package/busybox/0007-seedrng-fix-getrandom-detection-for-non-glibc-libc.patch
> new file mode 100644
> index 0000000000..90cace7968
> --- /dev/null
> +++ b/package/busybox/0007-seedrng-fix-getrandom-detection-for-non-glibc-libc.patch
> @@ -0,0 +1,106 @@
> +From b8d32dba741daea2ed01a0da32083b1bc994aa04 Mon Sep 17 00:00:00 2001
> +From: =?UTF-8?q?Rapha=C3=ABl=20M=C3=A9lotte?= <raphael.melotte@mind.be>
> +Date: Tue, 18 Apr 2023 15:54:43 +0200
> +Subject: [PATCH] seedrng: fix getrandom() detection for non-glibc libc
> +MIME-Version: 1.0
> +Content-Type: text/plain; charset=UTF-8
> +Content-Transfer-Encoding: 8bit
> +
> +glibc <= 2.24 does not provide getrandom(). A check for it has been
> +added in 200a9669fbf6f06894e4243cccc9fc11a1a6073a and fixed in
> +cb57abb46f06f4ede8d9ccbdaac67377fdf416cf.
> +
> +However, building with a libc other than glibc can lead to the same
> +problem as not every other libc has getrandom() either:
> +
> +- uClibc provides it from v1.0.2 onwards, but requires to define
> +_GNU_SOURCE (all versions - we already define it by default), and
> +stddef to be included first (when using uClibc < 1.0.35 - we already
> +include it through libbb.h).
> +
> +- musl libc has getrandom(), but only from version 1.1.20 onwards. As
> +musl does not provide __MUSL__ or version information, it's not
> +possible to check for it like we did for glibc.
> +
> +All of this makes it difficult (or impossible in case of musl) to
> +check what we need to do to have getrandom() based on each libc
> +versions.
> +
> +On top of that, getrandom() is also not available on older kernels. As
> +an example, when using a 3.10 kernel with uClibc 1.0.26, getrandom()
> +is declared so compiling works, but it fails at link time because
> +getrandom() is not defined.
> +
> +To make it easier, take a similar approach to what was done for the
> +crypt library: try to build a sample program to see if we have
> +getrandom().
> +
> +Based on the new Makefile variable, we now either use the
> +libc-provided getrandom() when it's available, or use our own
> +implementation when it's not (like it was the case already for glibc <
> +2.25).
> +
> +This should fix compiling with many libc/kernel combinations.
> +
> +Signed-off-by: Raphaël Mélotte <raphael.melotte@mind.be>
> +Upstream: http://lists.busybox.net/pipermail/busybox/2023-April/090285.html
> +---
> +Note that I was not able to test every single combination, but I could
> +confirm it builds successfully for:
> +uClibc 10.0.24, linux headers 3.10 (libc getrandom NOT used)
> +uClibc 1.0.36, linux headers 4.9 (libc getrandom used)
> +musl 1.1.16, linux headers 4.12 (libc getrandom NOT used)
> +musl 1.2.1, linux headers (libc getrandom used)
> +glibc 2.25, linux headers 4.10 (libc getrandom used)
> +
> + Makefile.flags      | 7 +++++++
> + miscutils/seedrng.c | 8 ++++----
> + 2 files changed, 11 insertions(+), 4 deletions(-)
> +
> +diff --git a/Makefile.flags b/Makefile.flags
> +index 1cec5ba20..88c11862f 100644
> +--- a/Makefile.flags
> ++++ b/Makefile.flags
> +@@ -161,6 +161,13 @@ ifeq ($(RT_AVAILABLE),y)
> + LDLIBS += rt
> + endif
> + 
> ++# Not all libc versions have getrandom, so check for it.
> ++HAVE_GETRANDOM := $(shell printf '#include <stddef.h>\n#include <sys/random.h>\nint main(void){char buf[256];\ngetrandom(buf,sizeof(buf),GRND_NONBLOCK);}' >bb_libtest.c; $(CC) $(CFLAGS) $(CFLAGS_busybox) -D_GNU_SOURCE -o /dev/null bb_libtest.c >/dev/null 2>&1 && echo "y"; rm bb_libtest.c)

... this big line here...

Regards,
Yann E. MORIN.

> ++
> ++ifeq ($(HAVE_GETRANDOM),y)
> ++CFLAGS += -DHAVE_GETRANDOM
> ++endif
> ++
> + # libpam may use libpthread, libdl and/or libaudit.
> + # On some platforms that requires an explicit -lpthread, -ldl, -laudit.
> + # However, on *other platforms* it fails when some of those flags
> +diff --git a/miscutils/seedrng.c b/miscutils/seedrng.c
> +index 3bf6e2ea7..2f1e18c32 100644
> +--- a/miscutils/seedrng.c
> ++++ b/miscutils/seedrng.c
> +@@ -44,8 +44,10 @@
> + #include <linux/random.h>
> + #include <sys/file.h>
> + 
> +-/* Fix up glibc <= 2.24 not having getrandom() */
> +-#if defined(__GLIBC__) && __GLIBC__ == 2 && __GLIBC_MINOR__ <= 24
> ++/* Fix up some libc (e.g. glibc <= 2.24) not having getrandom() */
> ++#if defined HAVE_GETRANDOM
> ++#include <sys/random.h>
> ++#else /* No getrandom */
> + #include <sys/syscall.h>
> + static ssize_t getrandom(void *buffer, size_t length, unsigned flags)
> + {
> +@@ -56,8 +58,6 @@ static ssize_t getrandom(void *buffer, size_t length, unsigned flags)
> + 	return -1;
> + # endif
> + }
> +-#else
> +-#include <sys/random.h>
> + #endif
> + 
> + /* Apparently some headers don't ship with this yet. */
> +-- 
> +2.39.1
> +
> -- 
> 2.37.3
> 
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