| Message ID | 20230307140522.2311461-2-ardb@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Add support for LPA2 at stage1 and WXN | expand |
On Tue, Mar 07, 2023 at 03:04:23PM +0100, Ard Biesheuvel wrote: > Avoid build issues in the early C code related to the latent_entropy GCC > plugin, by incorporating the C flags fragment that disables it. > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Just to check, are you seeing issues today? IIUC the plugin only instruments functions which are explicitly marked with __latent_entropy, and if we're seeing that happen unexpectedly (or due to that being applying to __meminit / __init), we might need to do likewise for other noinstr code. Regardless, for this patch: Acked-by: Mark Rutland <mark.rutland@arm.com> Mark. > --- > arch/arm64/kernel/pi/Makefile | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm64/kernel/pi/Makefile b/arch/arm64/kernel/pi/Makefile > index 4c0ea3cd4ea406b6..c844a0546d7f0e62 100644 > --- a/arch/arm64/kernel/pi/Makefile > +++ b/arch/arm64/kernel/pi/Makefile > @@ -3,6 +3,7 @@ > > KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) -fpie \ > -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN) \ > + $(DISABLE_LATENT_ENTROPY_PLUGIN) \ > $(call cc-option,-mbranch-protection=none) \ > -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \ > -include $(srctree)/include/linux/hidden.h \ > -- > 2.39.2 > >
On Fri, 28 Apr 2023 at 11:38, Mark Rutland <mark.rutland@arm.com> wrote: > > On Tue, Mar 07, 2023 at 03:04:23PM +0100, Ard Biesheuvel wrote: > > Avoid build issues in the early C code related to the latent_entropy GCC > > plugin, by incorporating the C flags fragment that disables it. > > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > Just to check, are you seeing issues today? IIUC the plugin only instruments > functions which are explicitly marked with __latent_entropy, and if we're > seeing that happen unexpectedly (or due to that being applying to __meminit / > __init), we might need to do likewise for other noinstr code. > I don't quite remember, tbh, but it is unlikely that I would have written or included this patch without having run into some actual issue. > Regardless, for this patch: > > Acked-by: Mark Rutland <mark.rutland@arm.com> > Thanks,
On Fri, Apr 28, 2023 at 11:54:16AM +0100, Ard Biesheuvel wrote: > On Fri, 28 Apr 2023 at 11:38, Mark Rutland <mark.rutland@arm.com> wrote: > > > > On Tue, Mar 07, 2023 at 03:04:23PM +0100, Ard Biesheuvel wrote: > > > Avoid build issues in the early C code related to the latent_entropy GCC > > > plugin, by incorporating the C flags fragment that disables it. > > > > > > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > > > > Just to check, are you seeing issues today? IIUC the plugin only instruments > > functions which are explicitly marked with __latent_entropy, and if we're > > seeing that happen unexpectedly (or due to that being applying to __meminit / > > __init), we might need to do likewise for other noinstr code. > > > > I don't quite remember, tbh, but it is unlikely that I would have > written or included this patch without having run into some actual > issue. Sure. Looking at the series, from patch 15 onwards you mark portions of the PI code as __init. As __init currently implies __latent_entropy (which I think is a bit crazy as of itself...), that's why this'll start to fail. It would be nice if we could mention that in the commit message, e.g. | In subsequent patches we'll mark portions of the early C code as __init. | Unfortunarely, __init implies __latent_entropy, and this would result in the | early C code being instrumented in an unsafe manner. | | Disable the latent entropy plugin for the early C code. ... though my ack stands regardless of whether we add such wording. Mark. > > Regardless, for this patch: > > > > Acked-by: Mark Rutland <mark.rutland@arm.com> > > > > Thanks,
diff --git a/arch/arm64/kernel/pi/Makefile b/arch/arm64/kernel/pi/Makefile index 4c0ea3cd4ea406b6..c844a0546d7f0e62 100644 --- a/arch/arm64/kernel/pi/Makefile +++ b/arch/arm64/kernel/pi/Makefile @@ -3,6 +3,7 @@ KBUILD_CFLAGS := $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) -fpie \ -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN) \ + $(DISABLE_LATENT_ENTROPY_PLUGIN) \ $(call cc-option,-mbranch-protection=none) \ -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \ -include $(srctree)/include/linux/hidden.h \
Avoid build issues in the early C code related to the latent_entropy GCC plugin, by incorporating the C flags fragment that disables it. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- arch/arm64/kernel/pi/Makefile | 1 + 1 file changed, 1 insertion(+)