[Letux-kernel] [BUG v5.2-rc1] ARM build broken
keescook at chromium.org
Mon May 20 20:53:49 CEST 2019
[Adding Chris and Ard, who might have more compiler versions that me...]
On Mon, May 20, 2019 at 07:08:39PM +0200, H. Nikolaus Schaller wrote:
> > Am 20.05.2019 um 17:59 schrieb Kees Cook <keescook at chromium.org>:
> > On Mon, May 20, 2019 at 05:15:02PM +0200, H. Nikolaus Schaller wrote:
> >> Hi,
> >> it seems as if ARM build is broken since ARM now hard enables CONFIG_HAVE_GCC_PLUGINS
> >> which indirectly enables CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK. Compiling this breaks
> >> on my system (Darwin build host) due to conflicts in system headers and Linux headers.
> >> So how can I turn off all these GCC_PLUGINS?
> >> The offending patch seems to be
> >> security: Create "kernel hardening" config area
> >> especially the new "default y" for GCC_PLUGINS. After removing that line from
> >> scripts/gcc-plugins/Kconfig makes my compile succeed.
> > The intention is to enable it _if_ the plugins are available as part of
> > the build environment. The "default y" on GCC_PLUGINS is mediated by:
> > depends on HAVE_GCC_PLUGINS
> HAVE_GCC_PLUGINS has the following description:
> An arch should select this symbol if it supports building with
> GCC plugins.
> So an ARCH (ARM) selects it unconditionally of the build environment.
> > depends on PLUGIN_HOSTCC != ""
> Well, we have it set to "g++" for ages and it was not a problem.
> So both conditions are true.
PLUGIN_HOSTCC should have passed the scripts/gcc-plugin.sh test, so
that's correct. And the result (CONFIG_GCC_PLUGINS) is correct: it
doesn't enable or disable anything itself.
What you want is to disable CONFIG_STACKPROTECTOR_PER_TASK, which
is the knob for the feature:
bool "Use a unique stack canary value for each task"
depends on GCC_PLUGINS && STACKPROTECTOR && SMP && !XIP_DEFLATED_DATA
> Build error:
> HOSTCXX -fPIC scripts/gcc-plugins/arm_ssp_per_task_plugin.o - due to: scripts/gcc-plugins/gcc-common.h
> In file included from scripts/gcc-plugins/arm_ssp_per_task_plugin.c:3:0:
> scripts/gcc-plugins/gcc-common.h:153:0: warning: "__unused" redefined
> #define __unused __attribute__((__unused__))
Does the following patch fix your build? (I assume that line is just a
warning, but if not...)
diff --git a/scripts/gcc-plugins/gcc-common.h b/scripts/gcc-plugins/gcc-common.h
index 552d5efd7cb7..17f06079a712 100644
@@ -150,8 +150,12 @@ void print_gimple_expr(FILE *, gimple, int, int);
void dump_gimple_stmt(pretty_printer *, gimple, int, int);
#define __unused __attribute__((__unused__))
#define __visible __attribute__((visibility("default")))
#define DECL_NAME_POINTER(node) IDENTIFIER_POINTER(DECL_NAME(node))
#define DECL_NAME_LENGTH(node) IDENTIFIER_LENGTH(DECL_NAME(node))
> HOSTLLD -shared scripts/gcc-plugins/arm_ssp_per_task_plugin.so - due to target missing
> Undefined symbols for architecture x86_64:
> "gen_reg_rtx(machine_mode)", referenced from:
> (anonymous namespace)::arm_pertask_ssp_rtl_pass::execute() in arm_ssp_per_task_plugin.o
However, this part sounds more like what was fixed with
259799ea5a9a ("gcc-plugins: arm_ssp_per_task_plugin: Fix for older GCC < 6")
And maybe some additional fixes for 4.9 are needed?
> This is because CONFIG_GCC_PLUGIN_ARM_SSP_PER_TASK became automatically enabled and was never
> before. So the compiler may lack some library search path for building this plugin (which we
> did never miss).
Right -- maybe CONFIG_STACKPROTECTOR_PER_TASK doesn't work with old gcc
4.9.2? I'll see if I can find that compiler version...
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