| Message ID | 20230619143725.57967-1-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ARM: change link order of $(mmy-y) to avoid veneers | expand |
On Mon, Jun 19, 2023 at 11:37 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > The kernel compiled with multi_v7_defconfig + CONFIG_KASAN=y + > CONFIG_KASAN_INLINE=y does not boot. > > I do not think KASAN is the direct reason of the boot failure. > CONFIG_KASAN_INLINE is just one example configuration that grows the > image size significantly and makes a big distance between function > callers and callees. > > I see some veneers for __get_user_* in the bad kernel image. I am > not perfectly clear, but __get_user_* may not work with veneers for > some reasons. > > If I move the link order of arch/arm/lib/getuser.S, the veneers are > gone, and the kernel gets working again. > > I do not see a good reason that $(mmu-y) must be added to lib-y because > all the code in $(mmu-y) is mandatory. Add it to obj-y to move the code > to lower address. > > [1] multi_v7_defconfig (works) > > $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 > c072a450 T __get_user_1 > c17ea033 r __kstrtab___get_user_1 > c18119fe r __kstrtabns___get_user_1 > c17c4878 r __ksymtab___get_user_1 > > [2] multi_v7_defconfig + CONFIG_KASAN_INLINE (does not work) > > $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 > c341ec2c T __get_user_1 > c06e3580 t ____get_user_1_veneer > c0adc6c0 t ____get_user_1_veneer > c12cf054 t ____get_user_1_veneer > c43f42cc r __kstrtab___get_user_1 > c441c128 r __kstrtabns___get_user_1 > c43cead8 r __ksymtab___get_user_1 > > [3] multi_v7_defconfig + CONFIG_KASAN_INLINE + this patch (works) > > $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 > c10975b0 T __get_user_1 > c43f42cc r __kstrtab___get_user_1 > c441c128 r __kstrtabns___get_user_1 > c43cead8 r __ksymtab___get_user_1 > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > --- > > arch/arm/lib/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile > index 650404be6768..4d092ef87a1d 100644 > --- a/arch/arm/lib/Makefile > +++ b/arch/arm/lib/Makefile > @@ -28,7 +28,7 @@ endif > # using lib_ here won't override already available weak symbols > obj-$(CONFIG_UACCESS_WITH_MEMCPY) += uaccess_with_memcpy.o > > -lib-$(CONFIG_MMU) += $(mmu-y) > +obj-$(CONFIG_MMU) += $(mmu-y) > > ifeq ($(CONFIG_CPU_32v3),y) > lib-y += io-readsw-armv3.o io-writesw-armv3.o > -- > 2.39.2 > I also wonder why __get_user* is defined in arch/arm/lib/ instead of arch/arm/kernel/, but I might be a convention. x86 puts it in the lib directory, arch/x86/lib/getuser.S then other architectures copy the code structure.
Subject: [PATCH] ARM: change link order of $(mmy-y) to avoid veneers There is a typo in the subject (mmy-y -> mmu-y). Kind regards, Nicolas On Mon, Jun 19, 2023 at 11:37:25PM +0900, Masahiro Yamada wrote: > The kernel compiled with multi_v7_defconfig + CONFIG_KASAN=y + > CONFIG_KASAN_INLINE=y does not boot. > > I do not think KASAN is the direct reason of the boot failure. > CONFIG_KASAN_INLINE is just one example configuration that grows the > image size significantly and makes a big distance between function > callers and callees. > > I see some veneers for __get_user_* in the bad kernel image. I am > not perfectly clear, but __get_user_* may not work with veneers for > some reasons. > > If I move the link order of arch/arm/lib/getuser.S, the veneers are > gone, and the kernel gets working again. > > I do not see a good reason that $(mmu-y) must be added to lib-y because > all the code in $(mmu-y) is mandatory. Add it to obj-y to move the code > to lower address. > > [1] multi_v7_defconfig (works) > > $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 > c072a450 T __get_user_1 > c17ea033 r __kstrtab___get_user_1 > c18119fe r __kstrtabns___get_user_1 > c17c4878 r __ksymtab___get_user_1 > > [2] multi_v7_defconfig + CONFIG_KASAN_INLINE (does not work) > > $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 > c341ec2c T __get_user_1 > c06e3580 t ____get_user_1_veneer > c0adc6c0 t ____get_user_1_veneer > c12cf054 t ____get_user_1_veneer > c43f42cc r __kstrtab___get_user_1 > c441c128 r __kstrtabns___get_user_1 > c43cead8 r __ksymtab___get_user_1 > > [3] multi_v7_defconfig + CONFIG_KASAN_INLINE + this patch (works) > > $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 > c10975b0 T __get_user_1 > c43f42cc r __kstrtab___get_user_1 > c441c128 r __kstrtabns___get_user_1 > c43cead8 r __ksymtab___get_user_1 > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > --- > > arch/arm/lib/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile > index 650404be6768..4d092ef87a1d 100644 > --- a/arch/arm/lib/Makefile > +++ b/arch/arm/lib/Makefile > @@ -28,7 +28,7 @@ endif > # using lib_ here won't override already available weak symbols > obj-$(CONFIG_UACCESS_WITH_MEMCPY) += uaccess_with_memcpy.o > > -lib-$(CONFIG_MMU) += $(mmu-y) > +obj-$(CONFIG_MMU) += $(mmu-y) > > ifeq ($(CONFIG_CPU_32v3),y) > lib-y += io-readsw-armv3.o io-writesw-armv3.o > -- > 2.39.2 >
On Mon, Jun 19, 2023 at 10:37 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > The kernel compiled with multi_v7_defconfig + CONFIG_KASAN=y + > CONFIG_KASAN_INLINE=y does not boot. > > I do not think KASAN is the direct reason of the boot failure. > CONFIG_KASAN_INLINE is just one example configuration that grows the > image size significantly and makes a big distance between function > callers and callees. > > I see some veneers for __get_user_* in the bad kernel image. I am > not perfectly clear, but __get_user_* may not work with veneers for > some reasons. I'm kind of curious to know more about this. Has there been other instances in the ARCH=arm port where "there must not be a veneer from X to Y for reason Z?" I thought the linker inserted veneers were meant to be transparent here. If you disassemble ____get_user_1_veneer, do they themselves branch to different symbols, or the same symbol? (Perhaps they trampoline to each other then the final one is the "call" to the original symbol). But perhaps the symbol at the end of the chain gives us more clues. I'd bet it's the KASAN callback, though does KASAN_INLINE inline those? Perhaps the veneer is corrupting a register? Maybe inline asm in the caller is missing a clobber for that register... > > If I move the link order of arch/arm/lib/getuser.S, the veneers are > gone, and the kernel gets working again. > > I do not see a good reason that $(mmu-y) must be added to lib-y because > all the code in $(mmu-y) is mandatory. Add it to obj-y to move the code > to lower address. > > [1] multi_v7_defconfig (works) > > $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 > c072a450 T __get_user_1 > c17ea033 r __kstrtab___get_user_1 > c18119fe r __kstrtabns___get_user_1 > c17c4878 r __ksymtab___get_user_1 > > [2] multi_v7_defconfig + CONFIG_KASAN_INLINE (does not work) > > $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 > c341ec2c T __get_user_1 > c06e3580 t ____get_user_1_veneer > c0adc6c0 t ____get_user_1_veneer > c12cf054 t ____get_user_1_veneer > c43f42cc r __kstrtab___get_user_1 > c441c128 r __kstrtabns___get_user_1 > c43cead8 r __ksymtab___get_user_1 > > [3] multi_v7_defconfig + CONFIG_KASAN_INLINE + this patch (works) > > $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 > c10975b0 T __get_user_1 > c43f42cc r __kstrtab___get_user_1 > c441c128 r __kstrtabns___get_user_1 > c43cead8 r __ksymtab___get_user_1 > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > --- > > arch/arm/lib/Makefile | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile > index 650404be6768..4d092ef87a1d 100644 > --- a/arch/arm/lib/Makefile > +++ b/arch/arm/lib/Makefile > @@ -28,7 +28,7 @@ endif > # using lib_ here won't override already available weak symbols > obj-$(CONFIG_UACCESS_WITH_MEMCPY) += uaccess_with_memcpy.o > > -lib-$(CONFIG_MMU) += $(mmu-y) > +obj-$(CONFIG_MMU) += $(mmu-y) > > ifeq ($(CONFIG_CPU_32v3),y) > lib-y += io-readsw-armv3.o io-writesw-armv3.o > -- > 2.39.2 >
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile index 650404be6768..4d092ef87a1d 100644 --- a/arch/arm/lib/Makefile +++ b/arch/arm/lib/Makefile @@ -28,7 +28,7 @@ endif # using lib_ here won't override already available weak symbols obj-$(CONFIG_UACCESS_WITH_MEMCPY) += uaccess_with_memcpy.o -lib-$(CONFIG_MMU) += $(mmu-y) +obj-$(CONFIG_MMU) += $(mmu-y) ifeq ($(CONFIG_CPU_32v3),y) lib-y += io-readsw-armv3.o io-writesw-armv3.o
The kernel compiled with multi_v7_defconfig + CONFIG_KASAN=y + CONFIG_KASAN_INLINE=y does not boot. I do not think KASAN is the direct reason of the boot failure. CONFIG_KASAN_INLINE is just one example configuration that grows the image size significantly and makes a big distance between function callers and callees. I see some veneers for __get_user_* in the bad kernel image. I am not perfectly clear, but __get_user_* may not work with veneers for some reasons. If I move the link order of arch/arm/lib/getuser.S, the veneers are gone, and the kernel gets working again. I do not see a good reason that $(mmu-y) must be added to lib-y because all the code in $(mmu-y) is mandatory. Add it to obj-y to move the code to lower address. [1] multi_v7_defconfig (works) $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 c072a450 T __get_user_1 c17ea033 r __kstrtab___get_user_1 c18119fe r __kstrtabns___get_user_1 c17c4878 r __ksymtab___get_user_1 [2] multi_v7_defconfig + CONFIG_KASAN_INLINE (does not work) $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 c341ec2c T __get_user_1 c06e3580 t ____get_user_1_veneer c0adc6c0 t ____get_user_1_veneer c12cf054 t ____get_user_1_veneer c43f42cc r __kstrtab___get_user_1 c441c128 r __kstrtabns___get_user_1 c43cead8 r __ksymtab___get_user_1 [3] multi_v7_defconfig + CONFIG_KASAN_INLINE + this patch (works) $ arm-linux-gnueabihf-nm vmlinux | grep __get_user_1 c10975b0 T __get_user_1 c43f42cc r __kstrtab___get_user_1 c441c128 r __kstrtabns___get_user_1 c43cead8 r __ksymtab___get_user_1 Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- arch/arm/lib/Makefile | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)