From: Masahiro Yamada <masahiroy@kernel.org>
To: linux-kbuild@vger.kernel.org
Cc: bpf <bpf@vger.kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Sam Ravnborg <sam@ravnborg.org>,
linux-kernel@vger.kernel.org,
Masahiro Yamada <masahiroy@kernel.org>
Subject: [PATCH v2 01/15] bpfilter: match bit size of bpfilter_umh to that of the kernel
Date: Wed, 29 Apr 2020 12:45:13 +0900 [thread overview]
Message-ID: <20200429034527.590520-2-masahiroy@kernel.org> (raw)
In-Reply-To: <20200429034527.590520-1-masahiroy@kernel.org>
bpfilter_umh is built for the default machine bit of the compiler,
which may not match to the bit size of the kernel.
This happens in the scenario below:
You can use biarch GCC that defaults to 64-bit for building the 32-bit
kernel. In this case, Kbuild passes -m32 to teach the compiler to
produce 32-bit kernel space objects. However, it is missing when
building bpfilter_umh. It is built as a 64-bit ELF, and then embedded
into the 32-bit kernel.
The 32-bit kernel and 64-bit umh is a bad combination.
In theory, we can have 32-bit umh running on 64-bit kernel, but we do
not have a good reason to support such a usecase.
The best is to match the bit size between them.
Pass -m32 or -m64 to the umh build command if it is found in
$(KBUILD_CFLAGS). Evaluate CC_CAN_LINK against the kernel bit-size.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---
Changes in v2:
- New patch
init/Kconfig | 4 +++-
net/bpfilter/Makefile | 5 +++--
usr/include/Makefile | 4 ++++
3 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/init/Kconfig b/init/Kconfig
index a494212a3a79..57562a8e2761 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -45,7 +45,9 @@ config CLANG_VERSION
default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
config CC_CAN_LINK
- def_bool $(success,$(srctree)/scripts/cc-can-link.sh $(CC))
+ bool
+ default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m64-flag)) if 64BIT
+ default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(m32-flag))
config CC_HAS_ASM_GOTO
def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
diff --git a/net/bpfilter/Makefile b/net/bpfilter/Makefile
index 36580301da70..f6209e4827b9 100644
--- a/net/bpfilter/Makefile
+++ b/net/bpfilter/Makefile
@@ -5,14 +5,15 @@
hostprogs := bpfilter_umh
bpfilter_umh-objs := main.o
-KBUILD_HOSTCFLAGS += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi
+KBUILD_HOSTCFLAGS += -I $(srctree)/tools/include/ -I $(srctree)/tools/include/uapi \
+ $(filter -m32 -m64, $(KBUILD_CFLAGS))
HOSTCC := $(CC)
ifeq ($(CONFIG_BPFILTER_UMH), y)
# builtin bpfilter_umh should be compiled with -static
# since rootfs isn't mounted at the time of __init
# function is called and do_execv won't find elf interpreter
-KBUILD_HOSTLDFLAGS += -static
+KBUILD_HOSTLDFLAGS += -static $(filter -m32 -m64, $(KBUILD_CFLAGS))
endif
$(obj)/bpfilter_umh_blob.o: $(obj)/bpfilter_umh
diff --git a/usr/include/Makefile b/usr/include/Makefile
index 5a7ee3e5ed86..55362f3ab393 100644
--- a/usr/include/Makefile
+++ b/usr/include/Makefile
@@ -8,6 +8,10 @@
# We cannot go as far as adding -Wpedantic since it emits too many warnings.
UAPI_CFLAGS := -std=c90 -Wall -Werror=implicit-function-declaration
+# In theory, we do not care -m32 or -m64 for header compile tests.
+# It is here just because CONFIG_CC_CAN_LINK is tested with -m32 or -m64.
+UAPI_CFLAGS += $(filter -m32 -m64, $(KBUILD_CFLAGS))
+
override c_flags = $(UAPI_CFLAGS) -Wp,-MMD,$(depfile) -I$(objtree)/usr/include
# The following are excluded for now because they fail to build.
--
2.25.1
next prev parent reply other threads:[~2020-04-29 3:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-29 3:45 [PATCH v2 00/15] kbuild: support 'userprogs' syntax Masahiro Yamada
2020-04-29 3:45 ` Masahiro Yamada [this message]
2020-04-29 3:45 ` [PATCH v2 02/15] kbuild: add infrastructure to build userspace programs Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 03/15] bpfilter: use 'userprogs' syntax to build bpfilter_umh Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 04/15] samples: seccomp: build sample programs for target architecture Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 05/15] kbuild: doc: document the new syntax 'userprogs' Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 06/15] samples: uhid: fix warnings in uhid-example Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 07/15] samples: uhid: build sample program for target architecture Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 08/15] samples: hidraw: " Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 09/15] samples: connector: " Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 10/15] samples: vfs: build sample programs " Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 11/15] samples: pidfd: build sample program " Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 12/15] samples: mei: " Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 13/15] samples: auxdisplay: use 'userprogs' syntax Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 14/15] samples: timers: " Masahiro Yamada
2020-04-29 3:45 ` [PATCH v2 15/15] samples: watchdog: " Masahiro Yamada
2020-05-12 4:34 ` [PATCH v2 00/15] kbuild: support " Masahiro Yamada
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200429034527.590520-2-masahiroy@kernel.org \
--to=masahiroy@kernel.org \
--cc=arnd@arndb.de \
--cc=bpf@vger.kernel.org \
--cc=linux-kbuild@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=sam@ravnborg.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).