Adding upstream version 6.7.7.upstream/6.7.7

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

15 files changed, 149 insertions, 135 deletions

diff --git a/arch/x86/lib/checksum_32.S b/arch/x86/lib/checksum_32.S
index 23318c338d..68f7fa3e13 100644
--- a/arch/x86/lib/checksum_32.S
+++ b/arch/x86/lib/checksum_32.S
@@ -21,10 +21,10 @@
  *                   converted to pure assembler
  */
 
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/errno.h>
 #include <asm/asm.h>
-#include <asm/export.h>
 #include <asm/nospec-branch.h>
 
 /*
diff --git a/arch/x86/lib/clear_page_64.S b/arch/x86/lib/clear_page_64.S
index f74a3e704a..2760a15fbc 100644
--- a/arch/x86/lib/clear_page_64.S
+++ b/arch/x86/lib/clear_page_64.S
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/asm.h>
-#include <asm/export.h>
 
 /*
  * Most CPUs support enhanced REP MOVSB/STOSB instructions. It is
diff --git a/arch/x86/lib/cmpxchg8b_emu.S b/arch/x86/lib/cmpxchg8b_emu.S
index 49805257b1..873e4ef23e 100644
--- a/arch/x86/lib/cmpxchg8b_emu.S
+++ b/arch/x86/lib/cmpxchg8b_emu.S
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <linux/export.h>
 #include <linux/linkage.h>
-#include <asm/export.h>
 #include <asm/percpu.h>
 #include <asm/processor-flags.h>
 
diff --git a/arch/x86/lib/copy_page_64.S b/arch/x86/lib/copy_page_64.S
index 30ea644bf4..d6ae793d08 100644
--- a/arch/x86/lib/copy_page_64.S
+++ b/arch/x86/lib/copy_page_64.S
@@ -1,10 +1,10 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /* Written 2003 by Andi Kleen, based on a kernel by Evandro Menezes */
 
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/cpufeatures.h>
 #include <asm/alternative.h>
-#include <asm/export.h>
 
 /*
  * Some CPUs run faster using the string copy instructions (sane microcode).
diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index 0a81aafed7..fc9fb5d061 100644
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -6,11 +6,11 @@
  * Functions to copy from and to user space.
  */
 
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/cpufeatures.h>
 #include <asm/alternative.h>
 #include <asm/asm.h>
-#include <asm/export.h>
 
 /*
  * rep_movs_alternative - memory copy with exception handling.
diff --git a/arch/x86/lib/copy_user_uncached_64.S b/arch/x86/lib/copy_user_uncached_64.S
index 5c5f38d326..2918e36eec 100644
--- a/arch/x86/lib/copy_user_uncached_64.S
+++ b/arch/x86/lib/copy_user_uncached_64.S
@@ -3,9 +3,9 @@
  * Copyright 2023 Linus Torvalds <torvalds@linux-foundation.org>
  */
 
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/asm.h>
-#include <asm/export.h>
 
 /*
  * copy_user_nocache - Uncached memory copy with exception handling
diff --git a/arch/x86/lib/csum-wrappers_64.c b/arch/x86/lib/csum-wrappers_64.c
index 145f9a0bde..f4df4d2415 100644
--- a/arch/x86/lib/csum-wrappers_64.c
+++ b/arch/x86/lib/csum-wrappers_64.c
@@ -14,8 +14,6 @@
  * @src: source address (user space)
  * @dst: destination address
  * @len: number of bytes to be copied.
- * @isum: initial sum that is added into the result (32bit unfolded)
- * @errp: set to -EFAULT for an bad source address.
  *
  * Returns an 32bit unfolded checksum of the buffer.
  * src and dst are best aligned to 64bits.
@@ -38,8 +36,6 @@ csum_and_copy_from_user(const void __user *src, void *dst, int len)
  * @src: source address
  * @dst: destination address (user space)
  * @len: number of bytes to be copied.
- * @isum: initial sum that is added into the result (32bit unfolded)
- * @errp: set to -EFAULT for an bad destination address.
  *
  * Returns an 32bit unfolded checksum of the buffer.
  * src and dst are best aligned to 64bits.
@@ -62,7 +58,6 @@ csum_and_copy_to_user(const void *src, void __user *dst, int len)
  * @src: source address
  * @dst: destination address
  * @len: number of bytes to be copied.
- * @sum: initial sum that is added into the result (32bit unfolded)
  *
  * Returns an 32bit unfolded checksum of the buffer.
  */
diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
index 9c63713477..10d5ed8b59 100644
--- a/arch/x86/lib/getuser.S
+++ b/arch/x86/lib/getuser.S
@@ -26,6 +26,7 @@
  * as they get called from within inline assembly.
  */
 
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/page_types.h>
 #include <asm/errno.h>
@@ -33,7 +34,6 @@
 #include <asm/thread_info.h>
 #include <asm/asm.h>
 #include <asm/smap.h>
-#include <asm/export.h>
 
 #define ASM_BARRIER_NOSPEC ALTERNATIVE "", "lfence", X86_FEATURE_LFENCE_RDTSC
 
@@ -163,23 +163,23 @@ SYM_CODE_END(__get_user_8_handle_exception)
 #endif
 
 /* get_user */
-	_ASM_EXTABLE(1b, __get_user_handle_exception)
-	_ASM_EXTABLE(2b, __get_user_handle_exception)
-	_ASM_EXTABLE(3b, __get_user_handle_exception)
+	_ASM_EXTABLE_UA(1b, __get_user_handle_exception)
+	_ASM_EXTABLE_UA(2b, __get_user_handle_exception)
+	_ASM_EXTABLE_UA(3b, __get_user_handle_exception)
 #ifdef CONFIG_X86_64
-	_ASM_EXTABLE(4b, __get_user_handle_exception)
+	_ASM_EXTABLE_UA(4b, __get_user_handle_exception)
 #else
-	_ASM_EXTABLE(4b, __get_user_8_handle_exception)
-	_ASM_EXTABLE(5b, __get_user_8_handle_exception)
+	_ASM_EXTABLE_UA(4b, __get_user_8_handle_exception)
+	_ASM_EXTABLE_UA(5b, __get_user_8_handle_exception)
 #endif
 
 /* __get_user */
-	_ASM_EXTABLE(6b, __get_user_handle_exception)
-	_ASM_EXTABLE(7b, __get_user_handle_exception)
-	_ASM_EXTABLE(8b, __get_user_handle_exception)
+	_ASM_EXTABLE_UA(6b, __get_user_handle_exception)
+	_ASM_EXTABLE_UA(7b, __get_user_handle_exception)
+	_ASM_EXTABLE_UA(8b, __get_user_handle_exception)
 #ifdef CONFIG_X86_64
-	_ASM_EXTABLE(9b, __get_user_handle_exception)
+	_ASM_EXTABLE_UA(9b, __get_user_handle_exception)
 #else
-	_ASM_EXTABLE(9b, __get_user_8_handle_exception)
-	_ASM_EXTABLE(10b, __get_user_8_handle_exception)
+	_ASM_EXTABLE_UA(9b, __get_user_8_handle_exception)
+	_ASM_EXTABLE_UA(10b, __get_user_8_handle_exception)
 #endif
diff --git a/arch/x86/lib/hweight.S b/arch/x86/lib/hweight.S
index 12c16c6aa4..774bdf3e6f 100644
--- a/arch/x86/lib/hweight.S
+++ b/arch/x86/lib/hweight.S
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/export.h>
 #include <linux/linkage.h>
-#include <asm/export.h>
 
 #include <asm/asm.h>
 
@@ -36,8 +36,12 @@ SYM_FUNC_START(__sw_hweight32)
 SYM_FUNC_END(__sw_hweight32)
 EXPORT_SYMBOL(__sw_hweight32)
 
-SYM_FUNC_START(__sw_hweight64)
+/*
+ * No 32-bit variant, because it's implemented as an inline wrapper
+ * on top of __arch_hweight32():
+ */
 #ifdef CONFIG_X86_64
+SYM_FUNC_START(__sw_hweight64)
 	pushq   %rdi
 	pushq   %rdx
 
@@ -66,18 +70,6 @@ SYM_FUNC_START(__sw_hweight64)
 	popq    %rdx
 	popq    %rdi
 	RET
-#else /* CONFIG_X86_32 */
-	/* We're getting an u64 arg in (%eax,%edx): unsigned long hweight64(__u64 w) */
-	pushl   %ecx
-
-	call    __sw_hweight32
-	movl    %eax, %ecx                      # stash away result
-	movl    %edx, %eax                      # second part of input
-	call    __sw_hweight32
-	addl    %ecx, %eax                      # result
-
-	popl    %ecx
-	RET
-#endif
 SYM_FUNC_END(__sw_hweight64)
 EXPORT_SYMBOL(__sw_hweight64)
+#endif
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index 76697df8df..0ae2e1712e 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -1,12 +1,12 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 /* Copyright 2002 Andi Kleen */
 
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <linux/cfi_types.h>
 #include <asm/errno.h>
 #include <asm/cpufeatures.h>
 #include <asm/alternative.h>
-#include <asm/export.h>
 
 .section .noinstr.text, "ax"
 
diff --git a/arch/x86/lib/memmove_32.S b/arch/x86/lib/memmove_32.S
index 0588b2c0fc..35010ba3dd 100644
--- a/arch/x86/lib/memmove_32.S
+++ b/arch/x86/lib/memmove_32.S
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 
+#include <linux/export.h>
 #include <linux/linkage.h>
-#include <asm/export.h>
 
 SYM_FUNC_START(memmove)
 /*
diff --git a/arch/x86/lib/memmove_64.S b/arch/x86/lib/memmove_64.S
index ccdf3a5970..1b60ae81ec 100644
--- a/arch/x86/lib/memmove_64.S
+++ b/arch/x86/lib/memmove_64.S
@@ -6,10 +6,10 @@
  * This assembly file is re-written from memmove_64.c file.
  *	- Copyright 2011 Fenghua Yu <fenghua.yu@intel.com>
  */
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/cpufeatures.h>
 #include <asm/alternative.h>
-#include <asm/export.h>
 
 #undef memmove
 
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S
index 3d818b849e..0199d56cb4 100644
--- a/arch/x86/lib/memset_64.S
+++ b/arch/x86/lib/memset_64.S
@@ -1,10 +1,10 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /* Copyright 2002 Andi Kleen, SuSE Labs */
 
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/cpufeatures.h>
 #include <asm/alternative.h>
-#include <asm/export.h>
 
 .section .noinstr.text, "ax"
 
diff --git a/arch/x86/lib/putuser.S b/arch/x86/lib/putuser.S
index 235bbda6fc..975c9c1826 100644
--- a/arch/x86/lib/putuser.S
+++ b/arch/x86/lib/putuser.S
@@ -11,13 +11,12 @@
  * return an error value in addition to the "real"
  * return value.
  */
+#include <linux/export.h>
 #include <linux/linkage.h>
 #include <asm/thread_info.h>
 #include <asm/errno.h>
 #include <asm/asm.h>
 #include <asm/smap.h>
-#include <asm/export.h>
-
 
 /*
  * __put_user_X
@@ -134,15 +133,15 @@ SYM_CODE_START_LOCAL(__put_user_handle_exception)
 	RET
 SYM_CODE_END(__put_user_handle_exception)
 
-	_ASM_EXTABLE(1b, __put_user_handle_exception)
-	_ASM_EXTABLE(2b, __put_user_handle_exception)
-	_ASM_EXTABLE(3b, __put_user_handle_exception)
-	_ASM_EXTABLE(4b, __put_user_handle_exception)
-	_ASM_EXTABLE(5b, __put_user_handle_exception)
-	_ASM_EXTABLE(6b, __put_user_handle_exception)
-	_ASM_EXTABLE(7b, __put_user_handle_exception)
-	_ASM_EXTABLE(9b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(1b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(2b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(3b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(4b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(5b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(6b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(7b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(9b, __put_user_handle_exception)
 #ifdef CONFIG_X86_32
-	_ASM_EXTABLE(8b, __put_user_handle_exception)
-	_ASM_EXTABLE(10b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(8b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(10b, __put_user_handle_exception)
 #endif
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index cd86aeb5fd..7b2589877d 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -1,12 +1,12 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 
+#include <linux/export.h>
 #include <linux/stringify.h>
 #include <linux/linkage.h>
 #include <asm/dwarf2.h>
 #include <asm/cpufeatures.h>
 #include <asm/alternative.h>
 #include <asm/asm-offsets.h>
-#include <asm/export.h>
 #include <asm/nospec-branch.h>
 #include <asm/unwind_hints.h>
 #include <asm/percpu.h>
@@ -126,11 +126,19 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
 #include <asm/GEN-for-each-reg.h>
 #undef GEN
 #endif
+
+#ifdef CONFIG_RETHUNK
+
 /*
- * This function name is magical and is used by -mfunction-return=thunk-extern
- * for the compiler to generate JMPs to it.
+ * Be careful here: that label cannot really be removed because in
+ * some configurations and toolchains, the JMP __x86_return_thunk the
+ * compiler issues is either a short one or the compiler doesn't use
+ * relocations for same-section JMPs and that breaks the returns
+ * detection logic in apply_returns() and in objtool.
  */
-#ifdef CONFIG_RETHUNK
+	.section .text..__x86.return_thunk
+
+#ifdef CONFIG_CPU_SRSO
 
 /*
  * srso_alias_untrain_ret() and srso_alias_safe_ret() are placed at
@@ -147,29 +155,18 @@ SYM_CODE_END(__x86_indirect_jump_thunk_array)
  *
  * As a result, srso_alias_safe_ret() becomes a safe return.
  */
-#ifdef CONFIG_CPU_SRSO
-	.section .text..__x86.rethunk_untrain
-
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+	.pushsection .text..__x86.rethunk_untrain
+SYM_CODE_START_NOALIGN(srso_alias_untrain_ret)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	ASM_NOP2
 	lfence
 	jmp srso_alias_return_thunk
 SYM_FUNC_END(srso_alias_untrain_ret)
-__EXPORT_THUNK(srso_alias_untrain_ret)
-
-	.section .text..__x86.rethunk_safe
-#else
-/* dummy definition for alternatives */
-SYM_START(srso_alias_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_FUNC_END(srso_alias_untrain_ret)
-#endif
+	.popsection
 
-SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
+	.pushsection .text..__x86.rethunk_safe
+SYM_CODE_START_NOALIGN(srso_alias_safe_ret)
 	lea 8(%_ASM_SP), %_ASM_SP
 	UNWIND_HINT_FUNC
 	ANNOTATE_UNRET_SAFE
@@ -177,14 +174,63 @@ SYM_START(srso_alias_safe_ret, SYM_L_GLOBAL, SYM_A_NONE)
 	int3
 SYM_FUNC_END(srso_alias_safe_ret)
 
-	.section .text..__x86.return_thunk
-
-SYM_CODE_START(srso_alias_return_thunk)
+SYM_CODE_START_NOALIGN(srso_alias_return_thunk)
 	UNWIND_HINT_FUNC
 	ANNOTATE_NOENDBR
 	call srso_alias_safe_ret
 	ud2
 SYM_CODE_END(srso_alias_return_thunk)
+	.popsection
+
+/*
+ * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
+ * above. On kernel entry, srso_untrain_ret() is executed which is a
+ *
+ * movabs $0xccccc30824648d48,%rax
+ *
+ * and when the return thunk executes the inner label srso_safe_ret()
+ * later, it is a stack manipulation and a RET which is mispredicted and
+ * thus a "safe" one to use.
+ */
+	.align 64
+	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
+SYM_CODE_START_LOCAL_NOALIGN(srso_untrain_ret)
+	ANNOTATE_NOENDBR
+	.byte 0x48, 0xb8
+
+/*
+ * This forces the function return instruction to speculate into a trap
+ * (UD2 in srso_return_thunk() below).  This RET will then mispredict
+ * and execution will continue at the return site read from the top of
+ * the stack.
+ */
+SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
+	lea 8(%_ASM_SP), %_ASM_SP
+	ret
+	int3
+	int3
+	/* end of movabs */
+	lfence
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_safe_ret)
+SYM_FUNC_END(srso_untrain_ret)
+
+SYM_CODE_START(srso_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	call srso_safe_ret
+	ud2
+SYM_CODE_END(srso_return_thunk)
+
+#define JMP_SRSO_UNTRAIN_RET "jmp srso_untrain_ret"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "jmp srso_alias_untrain_ret"
+#else /* !CONFIG_CPU_SRSO */
+#define JMP_SRSO_UNTRAIN_RET "ud2"
+#define JMP_SRSO_ALIAS_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_SRSO */
+
+#ifdef CONFIG_CPU_UNRET_ENTRY
 
 /*
  * Some generic notes on the untraining sequences:
@@ -216,7 +262,7 @@ SYM_CODE_END(srso_alias_return_thunk)
  */
 	.align 64
 	.skip 64 - (retbleed_return_thunk - retbleed_untrain_ret), 0xcc
-SYM_START(retbleed_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
+SYM_CODE_START_LOCAL_NOALIGN(retbleed_untrain_ret)
 	ANNOTATE_NOENDBR
 	/*
 	 * As executed from retbleed_untrain_ret, this is:
@@ -264,72 +310,27 @@ SYM_CODE_END(retbleed_return_thunk)
 	jmp retbleed_return_thunk
 	int3
 SYM_FUNC_END(retbleed_untrain_ret)
-__EXPORT_THUNK(retbleed_untrain_ret)
 
-/*
- * SRSO untraining sequence for Zen1/2, similar to retbleed_untrain_ret()
- * above. On kernel entry, srso_untrain_ret() is executed which is a
- *
- * movabs $0xccccc30824648d48,%rax
- *
- * and when the return thunk executes the inner label srso_safe_ret()
- * later, it is a stack manipulation and a RET which is mispredicted and
- * thus a "safe" one to use.
- */
-	.align 64
-	.skip 64 - (srso_safe_ret - srso_untrain_ret), 0xcc
-SYM_START(srso_untrain_ret, SYM_L_GLOBAL, SYM_A_NONE)
-	ANNOTATE_NOENDBR
-	.byte 0x48, 0xb8
+#define JMP_RETBLEED_UNTRAIN_RET "jmp retbleed_untrain_ret"
+#else /* !CONFIG_CPU_UNRET_ENTRY */
+#define JMP_RETBLEED_UNTRAIN_RET "ud2"
+#endif /* CONFIG_CPU_UNRET_ENTRY */
 
-/*
- * This forces the function return instruction to speculate into a trap
- * (UD2 in srso_return_thunk() below).  This RET will then mispredict
- * and execution will continue at the return site read from the top of
- * the stack.
- */
-SYM_INNER_LABEL(srso_safe_ret, SYM_L_GLOBAL)
-	lea 8(%_ASM_SP), %_ASM_SP
-	ret
-	int3
-	int3
-	/* end of movabs */
-	lfence
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_safe_ret)
-SYM_FUNC_END(srso_untrain_ret)
-__EXPORT_THUNK(srso_untrain_ret)
-
-SYM_CODE_START(srso_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	call srso_safe_ret
-	ud2
-SYM_CODE_END(srso_return_thunk)
+#if defined(CONFIG_CPU_UNRET_ENTRY) || defined(CONFIG_CPU_SRSO)
 
 SYM_FUNC_START(entry_untrain_ret)
-	ALTERNATIVE_2 "jmp retbleed_untrain_ret", \
-		      "jmp srso_untrain_ret", X86_FEATURE_SRSO, \
-		      "jmp srso_alias_untrain_ret", X86_FEATURE_SRSO_ALIAS
+	ALTERNATIVE_2 JMP_RETBLEED_UNTRAIN_RET,				\
+		      JMP_SRSO_UNTRAIN_RET, X86_FEATURE_SRSO,		\
+		      JMP_SRSO_ALIAS_UNTRAIN_RET, X86_FEATURE_SRSO_ALIAS
 SYM_FUNC_END(entry_untrain_ret)
 __EXPORT_THUNK(entry_untrain_ret)
 
-SYM_CODE_START(__x86_return_thunk)
-	UNWIND_HINT_FUNC
-	ANNOTATE_NOENDBR
-	ANNOTATE_UNRET_SAFE
-	ret
-	int3
-SYM_CODE_END(__x86_return_thunk)
-EXPORT_SYMBOL(__x86_return_thunk)
-
-#endif /* CONFIG_RETHUNK */
+#endif /* CONFIG_CPU_UNRET_ENTRY || CONFIG_CPU_SRSO */
 
 #ifdef CONFIG_CALL_DEPTH_TRACKING
 
 	.align 64
-SYM_FUNC_START(__x86_return_skl)
+SYM_FUNC_START(call_depth_return_thunk)
 	ANNOTATE_NOENDBR
 	/*
 	 * Keep the hotpath in a 16byte I-fetch for the non-debug
@@ -356,6 +357,33 @@ SYM_FUNC_START(__x86_return_skl)
 	ANNOTATE_UNRET_SAFE
 	ret
 	int3
-SYM_FUNC_END(__x86_return_skl)
+SYM_FUNC_END(call_depth_return_thunk)
 
 #endif /* CONFIG_CALL_DEPTH_TRACKING */
+
+/*
+ * This function name is magical and is used by -mfunction-return=thunk-extern
+ * for the compiler to generate JMPs to it.
+ *
+ * This code is only used during kernel boot or module init.  All
+ * 'JMP __x86_return_thunk' sites are changed to something else by
+ * apply_returns().
+ *
+ * This should be converted eventually to call a warning function which
+ * should scream loudly when the default return thunk is called after
+ * alternatives have been applied.
+ *
+ * That warning function cannot BUG() because the bug splat cannot be
+ * displayed in all possible configurations, leading to users not really
+ * knowing why the machine froze.
+ */
+SYM_CODE_START(__x86_return_thunk)
+	UNWIND_HINT_FUNC
+	ANNOTATE_NOENDBR
+	ANNOTATE_UNRET_SAFE
+	ret
+	int3
+SYM_CODE_END(__x86_return_thunk)
+EXPORT_SYMBOL(__x86_return_thunk)
+
+#endif /* CONFIG_RETHUNK */