[PATCH 0/2] tools/nolibc: add x32 support

[PATCH 0/2] tools/nolibc: add x32 support

[Thomas Weißschuh]

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
Thomas Weißschuh (2):
      tools/nolibc: define time_t in terms of __kernel_old_time_t
      selftests/nolibc: add x32 test configuration

 tools/include/nolibc/std.h                     |  4 +++-
 tools/testing/selftests/nolibc/Makefile.nolibc | 12 ++++++++++++
 tools/testing/selftests/nolibc/run-tests.sh    |  7 ++++++-
 3 files changed, 21 insertions(+), 2 deletions(-)
---
base-commit: 750aef513c610a37a13732ec64902428b839715e
change-id: 20250712-nolibc-x32-796a9da4c9ed

Best regards,
-- 
Thomas Weißschuh <linux@weissschuh.net>

[PATCH 1/2] tools/nolibc: define time_t in terms of __kernel_old_time_t

[Thomas Weißschuh]

Nolibc assumes that the kernel ABI is using a time values that are as
large as a long integer. For most ABIs this holds true.
But for x32 this is not correct, as it uses 32bit longs but 64bit times.

Also the 'struct stat' implementation of nolibc relies on timespec::tv_sec
and time_t being the same type. While timespec::tv_sec comes from the
kernel and is of type __kernel_old_time_t, time_t is defined within nolibc.

Switch to the __kernel_old_time_t to always get the correct type.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 tools/include/nolibc/std.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/include/nolibc/std.h b/tools/include/nolibc/std.h
index adda7333d12e7d2c336938ede1aaf215b4b93165..ba950f0e7338438823b4ee8c68a067391c719823 100644
--- a/tools/include/nolibc/std.h
+++ b/tools/include/nolibc/std.h
@@ -16,6 +16,8 @@
 #include "stdint.h"
 #include "stddef.h"
 
+#include <linux/types.h>
+
 /* those are commonly provided by sys/types.h */
 typedef unsigned int          dev_t;
 typedef unsigned long         ino_t;
@@ -27,6 +29,6 @@ typedef unsigned long       nlink_t;
 typedef   signed long         off_t;
 typedef   signed long     blksize_t;
 typedef   signed long      blkcnt_t;
-typedef   signed long        time_t;
+typedef __kernel_old_time_t  time_t;
 
 #endif /* _NOLIBC_STD_H */

-- 
2.50.1

[PATCH 2/2] selftests/nolibc: add x32 test configuration

[Thomas Weißschuh]

Nolibc supports the x32 ABI on x86.
Add a testcase to make sure the support stays functional.

QEMU user does not have support for x32, so skip the test there.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 tools/testing/selftests/nolibc/Makefile.nolibc | 12 ++++++++++++
 tools/testing/selftests/nolibc/run-tests.sh    |  7 ++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/nolibc/Makefile.nolibc b/tools/testing/selftests/nolibc/Makefile.nolibc
index 51ba853dd97eebed32f9808b0979460071f2514f..0fb759ba992ee6b1693b88f1b2e77463afa9f38b 100644
--- a/tools/testing/selftests/nolibc/Makefile.nolibc
+++ b/tools/testing/selftests/nolibc/Makefile.nolibc
@@ -47,6 +47,7 @@ XARCH_riscv      = riscv64
 XARCH            = $(or $(XARCH_$(ARCH)),$(ARCH))
 
 # map from user input variants to their kernel supported architectures
+ARCH_x32         = x86
 ARCH_armthumb    = arm
 ARCH_ppc         = powerpc
 ARCH_ppc64       = powerpc
@@ -68,6 +69,7 @@ ARCH            := $(or $(ARCH_$(XARCH)),$(XARCH))
 # kernel image names by architecture
 IMAGE_i386       = arch/x86/boot/bzImage
 IMAGE_x86_64     = arch/x86/boot/bzImage
+IMAGE_x32        = arch/x86/boot/bzImage
 IMAGE_x86        = arch/x86/boot/bzImage
 IMAGE_arm64      = arch/arm64/boot/Image
 IMAGE_arm        = arch/arm/boot/zImage
@@ -97,6 +99,7 @@ IMAGE_NAME       = $(notdir $(IMAGE))
 # default kernel configurations that appear to be usable
 DEFCONFIG_i386       = defconfig
 DEFCONFIG_x86_64     = defconfig
+DEFCONFIG_x32        = defconfig
 DEFCONFIG_x86        = defconfig
 DEFCONFIG_arm64      = defconfig
 DEFCONFIG_arm        = multi_v7_defconfig
@@ -122,6 +125,7 @@ DEFCONFIG_m68k       = virt_defconfig
 DEFCONFIG_sh4        = rts7751r2dplus_defconfig
 DEFCONFIG            = $(DEFCONFIG_$(XARCH))
 
+EXTRACONFIG_x32       = -e CONFIG_X86_X32_ABI
 EXTRACONFIG_arm       = -e CONFIG_NAMESPACES
 EXTRACONFIG_armthumb  = -e CONFIG_NAMESPACES
 EXTRACONFIG_m68k      = -e CONFIG_BLK_DEV_INITRD
@@ -134,6 +138,7 @@ TEST =
 # QEMU_ARCH: arch names used by qemu
 QEMU_ARCH_i386       = i386
 QEMU_ARCH_x86_64     = x86_64
+QEMU_ARCH_x32        = x86_64
 QEMU_ARCH_x86        = x86_64
 QEMU_ARCH_arm64      = aarch64
 QEMU_ARCH_arm        = arm
@@ -174,6 +179,7 @@ endif
 # QEMU_ARGS : some arch-specific args to pass to qemu
 QEMU_ARGS_i386       = -M pc -append "console=ttyS0,9600 i8042.noaux panic=-1 $(TEST:%=NOLIBC_TEST=%)"
 QEMU_ARGS_x86_64     = -M pc -append "console=ttyS0,9600 i8042.noaux panic=-1 $(TEST:%=NOLIBC_TEST=%)"
+QEMU_ARGS_x32        = -M pc -append "console=ttyS0,9600 i8042.noaux panic=-1 $(TEST:%=NOLIBC_TEST=%)"
 QEMU_ARGS_x86        = -M pc -append "console=ttyS0,9600 i8042.noaux panic=-1 $(TEST:%=NOLIBC_TEST=%)"
 QEMU_ARGS_arm64      = -M virt -cpu cortex-a53 -append "panic=-1 $(TEST:%=NOLIBC_TEST=%)"
 QEMU_ARGS_arm        = -M virt -append "panic=-1 $(TEST:%=NOLIBC_TEST=%)"
@@ -210,6 +216,7 @@ Q=@
 endif
 
 CFLAGS_i386 = $(call cc-option,-m32)
+CFLAGS_x32 = -mx32
 CFLAGS_arm = -marm
 CFLAGS_armthumb = -mthumb -march=armv6t2
 CFLAGS_ppc = -m32 -mbig-endian -mno-vsx $(call cc-option,-mmultiple)
@@ -236,6 +243,11 @@ LDFLAGS :=
 
 LIBGCC := -lgcc
 
+ifeq ($(ARCH),x86)
+# Not needed on x86, probably not present for x32
+LIBGCC :=
+endif
+
 ifneq ($(LLVM),)
 # Not needed for clang
 LIBGCC :=
diff --git a/tools/testing/selftests/nolibc/run-tests.sh b/tools/testing/selftests/nolibc/run-tests.sh
index 43eb30be316ae7bac7f0ba2c38b494a283833bec..e8af1fb505cf3573b4a6b37228dee764fe2e5277 100755
--- a/tools/testing/selftests/nolibc/run-tests.sh
+++ b/tools/testing/selftests/nolibc/run-tests.sh
@@ -18,7 +18,7 @@ test_mode=system
 werror=1
 llvm=
 all_archs=(
-	i386 x86_64
+	i386 x86_64 x32
 	arm64 arm armthumb
 	mips32le mips32be mipsn32le mipsn32be mips64le mips64be
 	ppc ppc64 ppc64le
@@ -115,6 +115,7 @@ crosstool_arch() {
 	mips*) echo mips;;
 	s390*) echo s390;;
 	sparc*) echo sparc64;;
+	x32*) echo x86_64;;
 	*) echo "$1";;
 	esac
 }
@@ -192,6 +193,10 @@ test_arch() {
 		echo "Unsupported configuration"
 		return
 	fi
+	if [ "$arch" = "x32" ] && [ "$test_mode" = "user" ]; then
+		echo "Unsupported configuration"
+		return
+	fi
 
 	mkdir -p "$build_dir"
 	swallow_output "${MAKE[@]}" defconfig

-- 
2.50.1

Re: [PATCH 1/2] tools/nolibc: define time_t in terms of __kernel_old_time_t

[Willy Tarreau]

On Sat, Jul 12, 2025 at 11:00:55AM +0200, Thomas Weißschuh wrote:
> Nolibc assumes that the kernel ABI is using a time values that are as
> large as a long integer. For most ABIs this holds true.
> But for x32 this is not correct, as it uses 32bit longs but 64bit times.
> 
> Also the 'struct stat' implementation of nolibc relies on timespec::tv_sec
> and time_t being the same type. While timespec::tv_sec comes from the
> kernel and is of type __kernel_old_time_t, time_t is defined within nolibc.
> 
> Switch to the __kernel_old_time_t to always get the correct type.
> 
> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Great! I didn't know we could support x32 and thought it was phased out.
But if it works it can be convenient for those seeking smaller binaries.

Both patches look good to me, for the whole series:

Acked-by: Willy Tarreau <w@1wt.eu>

Thanks!
Willy