x86/stackprotector: Work around strict Clang TLS symbol requirements

PATCH Superseded Ard Biesheuvel 4 participants 6 messages Oct 2, 2024 – Oct 9, 2024

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Stable branch x86 x86 entry code

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Ard Biesheuvel

author

2024-10-02 09:25 UTC #0 lore raw

PATCH 1/1 x86/stackprotector: Work around strict Clang TLS symbol requirements

From: Ard Biesheuvel <[email protected]>

GCC and Clang both implement stack protector support based on Thread Local Storage (TLS) variables, and this is used in the kernel to implement per-task stack cookies, by copying a task's stack cookie into a per-CPU variable every time it is scheduled in.

Both now also implement -mstack-protector-guard-symbol=, which permits the TLS variable to be specified directly. This is useful because it will allow us to move away from using a fixed offset of 40 bytes into the per-CPU area on x86_64, which requires a lot of special handling in the per-CPU code and the runtime relocation code.

However, while GCC is rather lax in its implementation of this command line option, Clang actually requires that the provided symbol name refers to a TLS variable (i.e., one declared with __thread), although it also permits the variable to be undeclared entirely, in which case it will use an implicit declaration of the right type.

The upshot of this is that Clang will emit the correct references to the stack cookie variable in most cases, e.g.,

10d: 64 a1 00 00 00 00 mov %fs:0x0,%eax

                      10f: R_386_32   __stack_chk_guard

However, if a non-TLS definition of the symbol in question is visible in the same compilation unit (which amounts to the whole of vmlinux if LTO is enabled), it will drop the per-CPU prefix and emit a load from a bogus address.

Work around this by using a symbol name that never occurs in C code, and emit it as an alias in the linker script.

Fixes 3fb0fdb3bbe7 ("x86/stackprotector/32: Make the canary into a regular percpu variable")

Cc <[email protected]>

Cc Fangrui Song <[email protected]>

Cc Brian Gerst <[email protected]>

Cc Uros Bizjak <[email protected]>

Cc Nathan Chancellor <[email protected]>

Cc Andy Lutomirski <[email protected]>

Link https://github.com/ClangBuiltLinux/linux/issues/1854

Signed-off-by Ard Biesheuvel <[email protected]>

---
 arch/x86/Makefile             |  5 +++--
 arch/x86/entry/entry.S        | 16 ++++++++++++++++
 arch/x86/kernel/cpu/common.c  |  2 ++
 arch/x86/kernel/vmlinux.lds.S |  3 +++
 4 files changed, 24 insertions(+), 2 deletions(-)

arch/x86/Makefile +3 -2

index cd75e78a06c1..5b773b34768d 100644
@@ -142,9 +142,10 @@ ifeq ($(CONFIG_X86_32),y)
 
     ifeq ($(CONFIG_STACKPROTECTOR),y)
         ifeq ($(CONFIG_SMP),y)
-			KBUILD_CFLAGS += -mstack-protector-guard-reg=fs -mstack-protector-guard-symbol=__stack_chk_guard
+            KBUILD_CFLAGS += -mstack-protector-guard-reg=fs \
+                             -mstack-protector-guard-symbol=__ref_stack_chk_guard
         else
-			KBUILD_CFLAGS += -mstack-protector-guard=global
+            KBUILD_CFLAGS += -mstack-protector-guard=global
         endif
     endif
 else

arch/x86/entry/entry.S +16 -0

index d9feadffa972..a503e6d535f8 100644
@@ -46,3 +46,19 @@ EXPORT_SYMBOL_GPL(mds_verw_sel);
 .popsection
 
 THUNK warn_thunk_thunk, __warn_thunk
+
+#ifndef CONFIG_X86_64
+/*
+ * Clang's implementation of TLS stack cookies requires the variable in
+ * question to be a TLS variable. If the variable happens to be defined as an
+ * ordinary variable with external linkage in the same compilation unit (which
+ * amounts to the whole of vmlinux with LTO enabled), Clang will drop the
+ * segment register prefix from the references, resulting in broken code. Work
+ * around this by avoiding the symbol used in -mstack-protector-guard-symbol=
+ * entirely in the C code, and use an alias emitted by the linker script
+ * instead.
+ */
+#ifdef CONFIG_STACKPROTECTOR
+EXPORT_SYMBOL(__ref_stack_chk_guard);
+#endif
+#endif

arch/x86/kernel/cpu/common.c +2 -0

index 07a34d723505..ba83f54dfaa8 100644
@@ -2085,8 +2085,10 @@ void syscall_init(void)
 
 #ifdef CONFIG_STACKPROTECTOR
 DEFINE_PER_CPU(unsigned long, __stack_chk_guard);
+#ifndef CONFIG_SMP
 EXPORT_PER_CPU_SYMBOL(__stack_chk_guard);
 #endif
+#endif
 
 #endif	/* CONFIG_X86_64 */

arch/x86/kernel/vmlinux.lds.S +3 -0

index 2b7c8c14c6fd..a80ad2bf8da4 100644
@@ -490,6 +490,9 @@ SECTIONS
 . = ASSERT((_end - LOAD_OFFSET <= KERNEL_IMAGE_SIZE),
 	   "kernel image bigger than KERNEL_IMAGE_SIZE");
 
+/* needed for Clang - see arch/x86/entry/entry.S */
+PROVIDE(__ref_stack_chk_guard = __stack_chk_guard);
+
 #ifdef CONFIG_X86_64
 /*
  * Per-cpu symbols which need to be offset from __per_cpu_load

Signature · 1 line

2.46.1.824.gd892dcdcdd-goog

Ard Biesheuvel

2024-10-02 11:04 UTC #1 lore raw

Quoted 43 lines · Ard Biesheuvel

From: Ard Biesheuvel <[email protected]>
GCC and Clang both implement stack protector support based on Thread Local Storage (TLS) variables, and this is used in the kernel to implement per-task stack cookies, by copying a task's stack cookie into a per-CPU variable every time it is scheduled in.
Both now also implement -mstack-protector-guard-symbol=, which permits the TLS variable to be specified directly. This is useful because it will allow us to move away from using a fixed offset of 40 bytes into the per-CPU area on x86_64, which requires a lot of special handling in the per-CPU code and the runtime relocation code.
However, while GCC is rather lax in its implementation of this command line option, Clang actually requires that the provided symbol name refers to a TLS variable (i.e., one declared with __thread), although it also permits the variable to be undeclared entirely, in which case it will use an implicit declaration of the right type.
The upshot of this is that Clang will emit the correct references to the stack cookie variable in most cases, e.g.,
   10d:       64 a1 00 00 00 00       mov    %fs:0x0,%eax
                      10f: R_386_32   __stack_chk_guard
However, if a non-TLS definition of the symbol in question is visible in the same compilation unit (which amounts to the whole of vmlinux if LTO is enabled), it will drop the per-CPU prefix and emit a load from a bogus address.
Work around this by using a symbol name that never occurs in C code, and emit it as an alias in the linker script.
Fixes 3fb0fdb3bbe7 ("x86/stackprotector/32: Make the canary into a regular percpu variable")
Cc <[email protected]>
Cc Fangrui Song <[email protected]>
Cc Brian Gerst <[email protected]>
Cc Uros Bizjak <[email protected]>
Cc Nathan Chancellor <[email protected]>
Cc Andy Lutomirski <[email protected]>
Link https://github.com/ClangBuiltLinux/linux/issues/1854
Signed-off-by Ard Biesheuvel <[email protected]>

Quoted 7 lines

---
 arch/x86/Makefile             |  5 +++--
 arch/x86/entry/entry.S        | 16 ++++++++++++++++
 arch/x86/kernel/cpu/common.c  |  2 ++
 arch/x86/kernel/vmlinux.lds.S |  3 +++
 4 files changed, 24 insertions(+), 2 deletions(-)

This needs the hunk below applied on top for CONFIG_MODVERSIONS:

arch/x86/include/asm/asm-prototypes.h +3 -0

@@ -20,3 +20,6 @@
 extern void cmpxchg8b_emu(void);
 #endif
 
+#ifdef CONFIG_STACKPROTECTOR
+extern unsigned long __ref_stack_chk_guard;
+#endif

Brian Gerst

2024-10-05 15:48 UTC #2 lore raw

Quoted 58 lines · Ard Biesheuvel

Quoted 43 lines · Ard Biesheuvel
From: Ard Biesheuvel <[email protected]>
GCC and Clang both implement stack protector support based on Thread Local Storage (TLS) variables, and this is used in the kernel to implement per-task stack cookies, by copying a task's stack cookie into a per-CPU variable every time it is scheduled in.
Both now also implement -mstack-protector-guard-symbol=, which permits the TLS variable to be specified directly. This is useful because it will allow us to move away from using a fixed offset of 40 bytes into the per-CPU area on x86_64, which requires a lot of special handling in the per-CPU code and the runtime relocation code.
However, while GCC is rather lax in its implementation of this command line option, Clang actually requires that the provided symbol name refers to a TLS variable (i.e., one declared with __thread), although it also permits the variable to be undeclared entirely, in which case it will use an implicit declaration of the right type.
The upshot of this is that Clang will emit the correct references to the stack cookie variable in most cases, e.g.,
   10d:       64 a1 00 00 00 00       mov    %fs:0x0,%eax
                      10f: R_386_32   __stack_chk_guard
However, if a non-TLS definition of the symbol in question is visible in the same compilation unit (which amounts to the whole of vmlinux if LTO is enabled), it will drop the per-CPU prefix and emit a load from a bogus address.
Work around this by using a symbol name that never occurs in C code, and emit it as an alias in the linker script.
Fixes 3fb0fdb3bbe7 ("x86/stackprotector/32: Make the canary into a regular percpu variable")
Cc <[email protected]>
Cc Fangrui Song <[email protected]>
Cc Brian Gerst <[email protected]>
Cc Uros Bizjak <[email protected]>
Cc Nathan Chancellor <[email protected]>
Cc Andy Lutomirski <[email protected]>
Link https://github.com/ClangBuiltLinux/linux/issues/1854
Signed-off-by Ard Biesheuvel <[email protected]>
Quoted 7 lines
---
 arch/x86/Makefile             |  5 +++--
 arch/x86/entry/entry.S        | 16 ++++++++++++++++
 arch/x86/kernel/cpu/common.c  |  2 ++
 arch/x86/kernel/vmlinux.lds.S |  3 +++
 4 files changed, 24 insertions(+), 2 deletions(-)
This needs the hunk below applied on top for CONFIG_MODVERSIONS:

arch/x86/include/asm/asm-prototypes.h line 25

Quoted 6 lines

arch/x86/include/asm/asm-prototypes.h +3 -0

@@ -20,3 +20,6 @@
 extern void cmpxchg8b_emu(void);
 #endif
 
+#ifdef CONFIG_STACKPROTECTOR
+extern unsigned long __ref_stack_chk_guard;
+#endif

Shouldn't this also be guarded by __GENKSYMS__, since the whole point of this is to hide the declaration from the compiler?

Brian Gerst

Ard Biesheuvel

2024-10-09 12:27 UTC #3 lore raw

Quoted 63 lines · Brian Gerst

Quoted 61 lines · Ard Biesheuvel
Quoted 43 lines · Ard Biesheuvel
From: Ard Biesheuvel <[email protected]>
GCC and Clang both implement stack protector support based on Thread Local Storage (TLS) variables, and this is used in the kernel to implement per-task stack cookies, by copying a task's stack cookie into a per-CPU variable every time it is scheduled in.
Both now also implement -mstack-protector-guard-symbol=, which permits the TLS variable to be specified directly. This is useful because it will allow us to move away from using a fixed offset of 40 bytes into the per-CPU area on x86_64, which requires a lot of special handling in the per-CPU code and the runtime relocation code.
However, while GCC is rather lax in its implementation of this command line option, Clang actually requires that the provided symbol name refers to a TLS variable (i.e., one declared with __thread), although it also permits the variable to be undeclared entirely, in which case it will use an implicit declaration of the right type.
The upshot of this is that Clang will emit the correct references to the stack cookie variable in most cases, e.g.,
   10d:       64 a1 00 00 00 00       mov    %fs:0x0,%eax
                      10f: R_386_32   __stack_chk_guard
However, if a non-TLS definition of the symbol in question is visible in the same compilation unit (which amounts to the whole of vmlinux if LTO is enabled), it will drop the per-CPU prefix and emit a load from a bogus address.
Work around this by using a symbol name that never occurs in C code, and emit it as an alias in the linker script.
Fixes 3fb0fdb3bbe7 ("x86/stackprotector/32: Make the canary into a regular percpu variable")
Cc <[email protected]>
Cc Fangrui Song <[email protected]>
Cc Brian Gerst <[email protected]>
Cc Uros Bizjak <[email protected]>
Cc Nathan Chancellor <[email protected]>
Cc Andy Lutomirski <[email protected]>
Link https://github.com/ClangBuiltLinux/linux/issues/1854
Signed-off-by Ard Biesheuvel <[email protected]>
Quoted 7 lines
---
 arch/x86/Makefile             |  5 +++--
 arch/x86/entry/entry.S        | 16 ++++++++++++++++
 arch/x86/kernel/cpu/common.c  |  2 ++
 arch/x86/kernel/vmlinux.lds.S |  3 +++
 4 files changed, 24 insertions(+), 2 deletions(-)
This needs the hunk below applied on top for CONFIG_MODVERSIONS:
arch/x86/include/asm/asm-prototypes.h +0 -0
@@ -20,3 +20,6 @@
 extern void cmpxchg8b_emu(void);
 #endif
 

Quoted 7 lines

arch/x86/include/asm/asm-prototypes.h line 25
Quoted 3 lines
arch/x86/include/asm/asm-prototypes.h +3 -0
+#ifdef CONFIG_STACKPROTECTOR
+extern unsigned long __ref_stack_chk_guard;
+#endif
Shouldn't this also be guarded by __GENKSYMS__, since the whole point of this is to hide the declaration from the compiler?

Yes, good point. Even though it does not matter in practice (the issue is tickled only by a visible *definition*, not by a declaration), this file is included into C code, which should be avoided.

kernel test robot

build bot

2024-10-03 14:17 UTC #4 lore raw

In reply to Ard Biesheuvel

kernel test robot noticed the following build warnings:

Hi Ard,

kernel test robot noticed the following build warnings:

[auto build test WARNING on tip/x86/core]
[also build test WARNING on tip/master linus/master tip/x86/asm v6.12-rc1 next-20241003] [cannot apply to tip/auto-latest]
[If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Ard-Biesheuvel/x86-stackprotector-Work-around-strict-Clang-TLS-symbol-requirements/20241002-172733
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/20241002092534.3163838-2-ardb%2Bgit%40google.com
patch subject: [PATCH] x86/stackprotector: Work around strict Clang TLS symbol requirements
config: i386-buildonly-randconfig-006-20241003 (https://download.01.org/0day-ci/archive/20241003/[email protected]/config)
compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241003/[email protected]/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All warnings (new ones prefixed by >>, old ones prefixed by <<):

WARNING: modpost: missing MODULE_DESCRIPTION() in arch/x86/mm/testmmiotrace.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/devfreq/governor_performance.o
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/devfreq/governor_powersave.o

>> WARNING: modpost: EXPORT symbol "__ref_stack_chk_guard" [vmlinux] version generation failed, symbol will not be versioned.
Is "__ref_stack_chk_guard" prototyped in <asm/asm-prototypes.h>?
>> WARNING: modpost: "__ref_stack_chk_guard" [arch/x86/events/amd/amd-uncore.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [arch/x86/events/intel/intel-uncore.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [arch/x86/kernel/apm.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [arch/x86/crypto/serpent-sse2-i586.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [arch/x86/platform/iris/iris.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [kernel/locking/locktorture.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [kernel/rcu/rcutorture.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [kernel/rcu/rcuscale.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [kernel/time/test_udelay.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [kernel/trace/ring_buffer_benchmark.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [kernel/backtracetest.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [fs/quota/quota_v1.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [fs/configfs/configfs.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [fs/nls/nls_base.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [fs/nls/nls_euc-jp.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [fs/nls/nls_utf8.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [fs/autofs/autofs4.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [fs/fuse/fuse.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [crypto/geniv.ko] has no CRC!

WARNING: modpost: "__ref_stack_chk_guard" [crypto/echainiv.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/crypto_null.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/xts.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/ctr.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/ccm.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/chacha20poly1305.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/cryptd.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/chacha_generic.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/authenc.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/authencesn.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/lzo.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/lzo-rle.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/essiv.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/ecdh_generic.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/crypto_simd.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/kunit/kunit-example-test.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/math/rational-test.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/crypto/libcurve25519-generic.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/crypto/libdes.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_hexdump.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/cpumask_kunit.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_hash.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_ubsan.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_vmalloc.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_scanf.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_xarray.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_maple_tree.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_lockup.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/842/842_compress.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/842/842_decompress.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/lzo/lzo_compress.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/overflow_kunit.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/siphash_kunit.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/bus/mhi/host/mhi.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/bus/mhi/host/mhi_pci_generic.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/allwinner/phy-sun6i-mipi-dphy.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/amlogic/phy-meson-g12a-usb3-pcie.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/intel/phy-intel-lgm-emmc.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/marvell/phy-berlin-sata.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/mediatek/phy-mtk-pcie.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/mediatek/phy-mtk-hdmi-drv.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/mediatek/phy-mtk-mipi-dsi-drv.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/qualcomm/phy-qcom-qmp-combo.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/qualcomm/phy-qcom-qmp-usbc.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/qualcomm/phy-qcom-qmp-usb-legacy.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/qualcomm/phy-qcom-snps-femto-v2.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/ralink/phy-ralink-usb.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/rockchip/phy-rockchip-pcie.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/ti/phy-da8xx-usb.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/ti/phy-am654-serdes.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/phy/ti/phy-j721e-wiz.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/freescale/pinctrl-imx.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/nuvoton/pinctrl-wpcm450.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/pxa/pinctrl-pxa25x.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/pxa/pinctrl-pxa27x.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/qcom/pinctrl-msm.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/qcom/pinctrl-ssbi-gpio.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/qcom/pinctrl-ssbi-mpp.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/qcom/pinctrl-lpass-lpi.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/sprd/pinctrl-sprd.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/pinctrl-da9062.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/pinctrl-max77620.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/pinctrl-microchip-sgpio.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/pinctrl-single.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pinctrl/meson/pinctrl-meson.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-104-dio-48e.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-aspeed.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-ath79.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-bd71815.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-cadence.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-da9055.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-eic-sprd.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-hlwd.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-idt3243x.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-lp873x.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-max77620.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-mc33880.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-pch.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-sch311x.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-sim.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-syscon.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-tps65912.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-ts4800.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-ts4900.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-uniphier.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-wm8994.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-xgene-sb.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpio/gpio-xra1403.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pci/hotplug/cpqphp.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pci/controller/pcie-altera.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pci/controller/pcie-mt7621.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/pci/pci-stub.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/video/backlight/ams369fg06.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/video/backlight/l4f00242t03.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/video/backlight/lms283gf05.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/video/backlight/88pm860x_bl.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/video/backlight/aat2870_bl.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/video/backlight/adp8870_bl.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/video/backlight/as3711_bl.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/video/backlight/backlight.ko] has no CRC!

Signature · 2 lines

0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

kernel test robot

build bot

2024-10-03 17:56 UTC #5 lore raw

In reply to Ard Biesheuvel

kernel test robot noticed the following build warnings:

Hi Ard,

kernel test robot noticed the following build warnings:

url:    https://github.com/intel-lab-lkp/linux/commits/Ard-Biesheuvel/x86-stackprotector-Work-around-strict-Clang-TLS-symbol-requirements/20241002-172733
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/20241002092534.3163838-2-ardb%2Bgit%40google.com
patch subject: [PATCH] x86/stackprotector: Work around strict Clang TLS symbol requirements
config: i386-randconfig-061-20241003 (https://download.01.org/0day-ci/archive/20241004/[email protected]/config)
compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241004/[email protected]/reproduce)

All warnings (new ones prefixed by >>, old ones prefixed by <<):

WARNING: modpost: missing MODULE_DESCRIPTION() in kernel/locking/test-ww_mutex.o
WARNING: modpost: EXPORT symbol "__ref_stack_chk_guard" [vmlinux] version generation failed, symbol will not be versioned. Is "__ref_stack_chk_guard" prototyped in <asm/asm-prototypes.h>?
WARNING: modpost: "__ref_stack_chk_guard" [kernel/rcu/refscale.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [kernel/torture.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [fs/nfs/nfsv4.ko] has no CRC!

>> WARNING: modpost: "__ref_stack_chk_guard" [fs/unicode/utf8-selftest.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [fs/smb/client/cifs.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [crypto/gcm.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [lib/kunit/kunit-test.ko] has no CRC!

WARNING: modpost: "__ref_stack_chk_guard" [lib/string_kunit.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/string_helpers_kunit.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_hexdump.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_hash.ko] has no CRC!

>> WARNING: modpost: "__ref_stack_chk_guard" [lib/test_printf.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_scanf.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_bitmap.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/test_uuid.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [lib/cmdline_kunit.ko] has no CRC!
>> WARNING: modpost: "__ref_stack_chk_guard" [lib/memcpy_kunit.ko] has no CRC!

WARNING: modpost: "__ref_stack_chk_guard" [lib/overflow_kunit.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/stackinit_kunit.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/fortify_kunit.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [lib/siphash_kunit.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpu/drm/tests/drm_cmdline_parser_test.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpu/drm/tests/drm_connector_test.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpu/drm/tests/drm_format_helper_test.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/gpu/drm/display/drm_display_helper.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/base/test/property-entry-test.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [drivers/power/supply/test_power.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [net/mptcp/mptcp_crypto_test.ko] has no CRC!
WARNING: modpost: "__ref_stack_chk_guard" [net/dns_resolver/dns_resolver.ko] has no CRC!

Signature · 2 lines

0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki