[PATCH 0/2] x86: Avoid CONFIG_X86_X32_ABI=y with llvm-objcopy

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Nathan Chancellor

14 Mar 2022 14 Mar '22

8:48 p.m.

This series disables CONFIG_X86_X32_ABI=y with llvm-objcopy, which has had two outstanding issues, which are further outlined in the second patch:

https://github.com/ClangBuiltLinux/linux/issues/514 https://github.com/ClangBuiltLinux/linux/issues/1141

The first patch is from Masahiro, which moves the CONFIG_X86_X32_ABI back into Kconfig proper. It was initially pushed as an RFC:

https://lore.kernel.org/r/20210227183910.221873-1-masahiroy@kernel.org/

The conclusion of that thread was that the check was still needed because of the two issues above. However, with the introduction of IBT, specifically commit 41c5ef31ad71 ("x86/ibt: Base IBT bits"), the second issue linked above becomes visible with allmodconfig, which heavily impacts automated testing.

The second patch builds on the first by just universally disabling CONFIG_X86_X32_ABI when using llvm-objcopy at configuration time so that neither issue is visible.

While it is unlikely that these issues will be fixed in LLVM, this could eventually become a version check.

This is based on -tip x86/core and I would like for both patches to go with the IBT changes so that there is no build breakage.

Masahiro Yamada (1): x86: Remove toolchain check for X32 ABI capability

Nathan Chancellor (1): x86/Kconfig: Do not allow CONFIG_X86_X32_ABI=y with llvm-objcopy

base-commit: f8afc9d88e65d189653f363eacc1f3131216ef7c

-- 2.35.1

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Nathan Chancellor

14 Mar 14 Mar

8:48 p.m.

New subject: [PATCH 1/2] x86: Remove toolchain check for X32 ABI capability

From: Masahiro Yamada masahiroy@kernel.org

Commit 0bf6276392e9 ("x32: Warn and disable rather than error if binutils too old") added a small test in arch/x86/Makefile because binutils 2.22 or newer is needed to properly support elf32-x86-64. This check is no longer necessary, as the minimum supported version of binutils is 2.23, which is enforced at configuration time with scripts/min-tool-version.sh.

Remove this check and replace all uses of CONFIG_X86_X32 with CONFIG_X86_X32_ABI, as two symbols are no longer necessary.

Signed-off-by: Masahiro Yamada masahiroy@kernel.org [nathan: Rebase, fix up a few places where CONFIG_X86_X32 was still used, and simplify commit message to satisfy -tip requirements] Signed-off-by: Nathan Chancellor nathan@kernel.org --- arch/x86/Kconfig | 8 ++------ arch/x86/Makefile | 16 ---------------- arch/x86/entry/syscalls/Makefile | 2 +- arch/x86/include/asm/syscall_wrapper.h | 6 +++--- arch/x86/include/asm/vdso.h | 2 +- arch/x86/kernel/process_64.c | 2 +- fs/fuse/ioctl.c | 2 +- fs/xfs/xfs_ioctl32.c | 2 +- sound/core/control_compat.c | 16 ++++++++-------- sound/core/pcm_compat.c | 20 ++++++++++---------- 10 files changed, 28 insertions(+), 48 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 870e0d10452d..b903bfcd713c 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2861,7 +2861,7 @@ config IA32_AOUT help Support old a.out binaries in the 32bit emulation.

-config X86_X32 +config X86_X32_ABI bool "x32 ABI for 64-bit mode" depends on X86_64 help @@ -2870,10 +2870,6 @@ config X86_X32 full 64-bit register file and wide data path while leaving pointers at 32 bits for smaller memory footprint.

- You will need a recent binutils (2.22 or later) with - elf32_x86_64 support enabled to compile a kernel with this - option set. - config COMPAT_32 def_bool y depends on IA32_EMULATION || X86_32 @@ -2882,7 +2878,7 @@ config COMPAT_32

config COMPAT def_bool y - depends on IA32_EMULATION || X86_X32 + depends on IA32_EMULATION || X86_X32_ABI

if COMPAT config COMPAT_FOR_U64_ALIGNMENT diff --git a/arch/x86/Makefile b/arch/x86/Makefile index f29c2c9c3216..63d50f65b828 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -152,22 +152,6 @@ else KBUILD_CFLAGS += -mcmodel=kernel endif

-ifdef CONFIG_X86_X32 - x32_ld_ok := $(call try-run,\ - /bin/echo -e '1: .quad 1b' | \ - $(CC) $(KBUILD_AFLAGS) -c -x assembler -o "$$TMP" - && \ - $(OBJCOPY) -O elf32-x86-64 "$$TMP" "$$TMP.o" && \ - $(LD) -m elf32_x86_64 "$$TMP.o" -o "$$TMP",y,n) - ifeq ($(x32_ld_ok),y) - CONFIG_X86_X32_ABI := y - KBUILD_AFLAGS += -DCONFIG_X86_X32_ABI - KBUILD_CFLAGS += -DCONFIG_X86_X32_ABI - else - $(warning CONFIG_X86_X32 enabled but no binutils support) - endif -endif -export CONFIG_X86_X32_ABI - # # If the function graph tracer is used with mcount instead of fentry, # '-maccumulate-outgoing-args' is needed to prevent a GCC bug diff --git a/arch/x86/entry/syscalls/Makefile b/arch/x86/entry/syscalls/Makefile index 5b3efed0e4e8..7f3886eeb2ff 100644 --- a/arch/x86/entry/syscalls/Makefile +++ b/arch/x86/entry/syscalls/Makefile @@ -67,7 +67,7 @@ uapisyshdr-y += unistd_32.h unistd_64.h unistd_x32.h syshdr-y += syscalls_32.h syshdr-$(CONFIG_X86_64) += unistd_32_ia32.h unistd_64_x32.h syshdr-$(CONFIG_X86_64) += syscalls_64.h -syshdr-$(CONFIG_X86_X32) += syscalls_x32.h +syshdr-$(CONFIG_X86_X32_ABI) += syscalls_x32.h syshdr-$(CONFIG_XEN) += xen-hypercalls.h

uapisyshdr-y := $(addprefix $(uapi)/, $(uapisyshdr-y)) diff --git a/arch/x86/include/asm/syscall_wrapper.h b/arch/x86/include/asm/syscall_wrapper.h index 6a2827d0681f..59358d1bf880 100644 --- a/arch/x86/include/asm/syscall_wrapper.h +++ b/arch/x86/include/asm/syscall_wrapper.h @@ -159,7 +159,7 @@ extern long __ia32_sys_ni_syscall(const struct pt_regs *regs); #endif /* CONFIG_IA32_EMULATION */

-#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI /* * For the x32 ABI, we need to create a stub for compat_sys_*() which is aware * of the x86-64-style parameter ordering of x32 syscalls. The syscalls common @@ -177,12 +177,12 @@ extern long __ia32_sys_ni_syscall(const struct pt_regs *regs);

#define __X32_COMPAT_SYS_NI(name) \ __SYS_NI(x64, compat_sys_##name) -#else /* CONFIG_X86_X32 */ +#else /* CONFIG_X86_X32_ABI */ #define __X32_COMPAT_SYS_STUB0(name) #define __X32_COMPAT_SYS_STUBx(x, name, ...) #define __X32_COMPAT_COND_SYSCALL(name) #define __X32_COMPAT_SYS_NI(name) -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */

#ifdef CONFIG_COMPAT diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h index 98aa103eb4ab..2963a2f5dbc4 100644 --- a/arch/x86/include/asm/vdso.h +++ b/arch/x86/include/asm/vdso.h @@ -37,7 +37,7 @@ struct vdso_image { extern const struct vdso_image vdso_image_64; #endif

-#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI extern const struct vdso_image vdso_image_x32; #endif

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 3402edec236c..e459253649be 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -681,7 +681,7 @@ void set_personality_64bit(void)

static void __set_personality_x32(void) { -#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI if (current->mm) current->mm->context.flags = 0;

diff --git a/fs/fuse/ioctl.c b/fs/fuse/ioctl.c index fbc09dab1f85..7143c85cc4aa 100644 --- a/fs/fuse/ioctl.c +++ b/fs/fuse/ioctl.c @@ -170,7 +170,7 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg, #else if (flags & FUSE_IOCTL_COMPAT) { inarg.flags |= FUSE_IOCTL_32BIT; -#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI if (in_x32_syscall()) inarg.flags |= FUSE_IOCTL_COMPAT_X32; #endif diff --git a/fs/xfs/xfs_ioctl32.c b/fs/xfs/xfs_ioctl32.c index 004ed2a251e8..ca25ed89b706 100644 --- a/fs/xfs/xfs_ioctl32.c +++ b/fs/xfs/xfs_ioctl32.c @@ -217,7 +217,7 @@ xfs_compat_ioc_fsbulkstat( inumbers_fmt_pf inumbers_func = xfs_fsinumbers_fmt_compat; bulkstat_one_fmt_pf bs_one_func = xfs_fsbulkstat_one_fmt_compat;

-#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI if (in_x32_syscall()) { /* * ... but on x32 the input xfs_fsop_bulkreq has pointers diff --git a/sound/core/control_compat.c b/sound/core/control_compat.c index edff063e088d..d8a86d1a99d6 100644 --- a/sound/core/control_compat.c +++ b/sound/core/control_compat.c @@ -150,7 +150,7 @@ struct snd_ctl_elem_value32 { unsigned char reserved[128]; };

-#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI /* x32 has a different alignment for 64bit values from ia32 */ struct snd_ctl_elem_value_x32 { struct snd_ctl_elem_id id; @@ -162,7 +162,7 @@ struct snd_ctl_elem_value_x32 { } value; unsigned char reserved[128]; }; -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */

/* get the value type and count of the control */ static int get_ctl_type(struct snd_card *card, struct snd_ctl_elem_id *id, @@ -347,7 +347,7 @@ static int snd_ctl_elem_write_user_compat(struct snd_ctl_file *file, return ctl_elem_write_user(file, data32, &data32->value); }

-#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI static int snd_ctl_elem_read_user_x32(struct snd_card *card, struct snd_ctl_elem_value_x32 __user *data32) { @@ -359,7 +359,7 @@ static int snd_ctl_elem_write_user_x32(struct snd_ctl_file *file, { return ctl_elem_write_user(file, data32, &data32->value); } -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */

/* add or replace a user control */ static int snd_ctl_elem_add_compat(struct snd_ctl_file *file, @@ -418,10 +418,10 @@ enum { SNDRV_CTL_IOCTL_ELEM_WRITE32 = _IOWR('U', 0x13, struct snd_ctl_elem_value32), SNDRV_CTL_IOCTL_ELEM_ADD32 = _IOWR('U', 0x17, struct snd_ctl_elem_info32), SNDRV_CTL_IOCTL_ELEM_REPLACE32 = _IOWR('U', 0x18, struct snd_ctl_elem_info32), -#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI SNDRV_CTL_IOCTL_ELEM_READ_X32 = _IOWR('U', 0x12, struct snd_ctl_elem_value_x32), SNDRV_CTL_IOCTL_ELEM_WRITE_X32 = _IOWR('U', 0x13, struct snd_ctl_elem_value_x32), -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */ };

static inline long snd_ctl_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) @@ -460,12 +460,12 @@ static inline long snd_ctl_ioctl_compat(struct file *file, unsigned int cmd, uns return snd_ctl_elem_add_compat(ctl, argp, 0); case SNDRV_CTL_IOCTL_ELEM_REPLACE32: return snd_ctl_elem_add_compat(ctl, argp, 1); -#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI case SNDRV_CTL_IOCTL_ELEM_READ_X32: return snd_ctl_elem_read_user_x32(ctl->card, argp); case SNDRV_CTL_IOCTL_ELEM_WRITE_X32: return snd_ctl_elem_write_user_x32(ctl, argp); -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */ }

down_read(&snd_ioctl_rwsem); diff --git a/sound/core/pcm_compat.c b/sound/core/pcm_compat.c index e4e176854ce7..917c5b4f19d7 100644 --- a/sound/core/pcm_compat.c +++ b/sound/core/pcm_compat.c @@ -147,13 +147,13 @@ static int snd_pcm_ioctl_channel_info_compat(struct snd_pcm_substream *substream return err; }

-#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI /* X32 ABI has the same struct as x86-64 for snd_pcm_channel_info */ static int snd_pcm_channel_info_user(struct snd_pcm_substream *substream, struct snd_pcm_channel_info __user *src); #define snd_pcm_ioctl_channel_info_x32(s, p) \ snd_pcm_channel_info_user(s, p) -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */

struct compat_snd_pcm_status64 { snd_pcm_state_t state; @@ -375,7 +375,7 @@ static int snd_pcm_ioctl_xfern_compat(struct snd_pcm_substream *substream, return err; }

-#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI /* X32 ABI has 64bit timespec and 64bit alignment */ struct snd_pcm_mmap_status_x32 { snd_pcm_state_t state; @@ -468,7 +468,7 @@ static int snd_pcm_ioctl_sync_ptr_x32(struct snd_pcm_substream *substream,

return 0; } -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */

#ifdef __BIG_ENDIAN typedef char __pad_before_u32[4]; @@ -560,10 +560,10 @@ enum { SNDRV_PCM_IOCTL_READN_FRAMES32 = _IOR('A', 0x53, struct snd_xfern32), SNDRV_PCM_IOCTL_STATUS_COMPAT64 = _IOR('A', 0x20, struct compat_snd_pcm_status64), SNDRV_PCM_IOCTL_STATUS_EXT_COMPAT64 = _IOWR('A', 0x24, struct compat_snd_pcm_status64), -#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI SNDRV_PCM_IOCTL_CHANNEL_INFO_X32 = _IOR('A', 0x32, struct snd_pcm_channel_info), SNDRV_PCM_IOCTL_SYNC_PTR_X32 = _IOWR('A', 0x23, struct snd_pcm_sync_ptr_x32), -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */ };

static long snd_pcm_ioctl_compat(struct file *file, unsigned int cmd, unsigned long arg) @@ -607,10 +607,10 @@ static long snd_pcm_ioctl_compat(struct file *file, unsigned int cmd, unsigned l case __SNDRV_PCM_IOCTL_SYNC_PTR32: return snd_pcm_common_ioctl(file, substream, cmd, argp); case __SNDRV_PCM_IOCTL_SYNC_PTR64: -#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI if (in_x32_syscall()) return snd_pcm_ioctl_sync_ptr_x32(substream, argp); -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */ return snd_pcm_ioctl_sync_ptr_buggy(substream, argp); case SNDRV_PCM_IOCTL_HW_REFINE32: return snd_pcm_ioctl_hw_params_compat(substream, 1, argp); @@ -642,10 +642,10 @@ static long snd_pcm_ioctl_compat(struct file *file, unsigned int cmd, unsigned l return snd_pcm_status_user_compat64(substream, argp, false); case SNDRV_PCM_IOCTL_STATUS_EXT_COMPAT64: return snd_pcm_status_user_compat64(substream, argp, true); -#ifdef CONFIG_X86_X32 +#ifdef CONFIG_X86_X32_ABI case SNDRV_PCM_IOCTL_CHANNEL_INFO_X32: return snd_pcm_ioctl_channel_info_x32(substream, argp); -#endif /* CONFIG_X86_X32 */ +#endif /* CONFIG_X86_X32_ABI */ }

return -ENOIOCTLCMD;

-- 2.35.1

Nathan Chancellor

8:48 p.m.

New subject: [PATCH 2/2] x86/Kconfig: Do not allow CONFIG_X86_X32_ABI=y with llvm-objcopy

There are two outstanding issues with CONFIG_X86_X32_ABI and llvm-objcopy, with similar root causes:

1. llvm-objcopy does not properly convert .note.gnu.property when going from x86_64 to x86_x32, resulting in a corrupted section when linking:

https://github.com/ClangBuiltLinux/linux/issues/1141

2. llvm-objcopy produces corrupted compressed debug sections when going from x86_64 to x86_x32, also resulting in an error when linking:

https://github.com/ClangBuiltLinux/linux/issues/514

After commit 41c5ef31ad71 ("x86/ibt: Base IBT bits"), the .note.gnu.property section is always generated when CONFIG_X86_KERNEL_IBT is enabled, which causes the first issue to become visible with an allmodconfig build:

ld.lld: error: arch/x86/entry/vdso/vclock_gettime-x32.o:(.note.gnu.property+0x1c): program property is too short

To avoid this error, do not allow CONFIG_X86_X32_ABI to be selected when using llvm-objcopy. If the two issues ever get fixed in llvm-objcopy, this can be turned into a feature check.

Signed-off-by: Nathan Chancellor nathan@kernel.org --- arch/x86/Kconfig | 5 +++++ 1 file changed, 5 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index b903bfcd713c..0f0672d2c816 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2864,6 +2864,11 @@ config IA32_AOUT config X86_X32_ABI bool "x32 ABI for 64-bit mode" depends on X86_64 + # llvm-objcopy does not convert x86_64 .note.gnu.property or + # compressed debug sections to x86_x32 properly: + # https://github.com/ClangBuiltLinux/linux/issues/514 + # https://github.com/ClangBuiltLinux/linux/issues/1141 + depends on $(success,$(OBJCOPY) --version | head -n1 | grep -qv llvm) help Include code to run binaries for the x32 native 32-bit ABI for 64-bit processors. An x32 process gets access to the

-- 2.35.1

Peter Zijlstra

9:13 p.m.

On Mon, Mar 14, 2022 at 12:48:40PM -0700, Nathan Chancellor wrote:

...

This is based on -tip x86/core and I would like for both patches to go with the IBT changes so that there is no build breakage.

Masahiro Yamada (1): x86: Remove toolchain check for X32 ABI capability

Nathan Chancellor (1): x86/Kconfig: Do not allow CONFIG_X86_X32_ABI=y with llvm-objcopy

Mucho gracias, I was indeed seeing a lot of that. I was also in the process of rebasing that tree, so I'll stick these on top.

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