add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/arch/x86/kernel/vmlinux.lds.S
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@@ -133,7 +133,20 @@
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 		LOCK_TEXT
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 		KPROBES_TEXT
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 		ALIGN_ENTRY_TEXT_BEGIN
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+#ifdef CONFIG_CPU_SRSO
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+		*(.text..__x86.rethunk_untrain)
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+#endif
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+
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 		ENTRY_TEXT
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+
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+#ifdef CONFIG_CPU_SRSO
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+		/*
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+		 * See the comment above srso_alias_untrain_ret()'s
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+		 * definition.
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+		 */
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+		. = srso_alias_untrain_ret | (1 << 2) | (1 << 8) | (1 << 14) | (1 << 20);
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+		*(.text..__x86.rethunk_safe)
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+#endif
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 		ALIGN_ENTRY_TEXT_END
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 		SOFTIRQENTRY_TEXT
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 		STATIC_CALL_TEXT
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@@ -142,13 +155,15 @@
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 #ifdef CONFIG_RETPOLINE
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 		__indirect_thunk_start = .;
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-		*(.text.__x86.*)
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+		*(.text..__x86.indirect_thunk)
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+		*(.text..__x86.return_thunk)
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 		__indirect_thunk_end = .;
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 #endif
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 	} :text =0xcccc
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 	/* End of text section, which should occupy whole number of pages */
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 	_etext = .;
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+
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 	. = ALIGN(PAGE_SIZE);
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 	X86_ALIGN_RODATA_BEGIN
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@@ -502,6 +517,27 @@
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            "fixed_percpu_data is not at start of per-cpu area");
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 #endif
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+#ifdef CONFIG_RETHUNK
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+. = ASSERT((retbleed_return_thunk & 0x3f) == 0, "retbleed_return_thunk not cacheline-aligned");
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+. = ASSERT((srso_safe_ret & 0x3f) == 0, "srso_safe_ret not cacheline-aligned");
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+#endif
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+
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+#ifdef CONFIG_CPU_SRSO
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+/*
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+ * GNU ld cannot do XOR until 2.41.
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+ * https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=f6f78318fca803c4907fb8d7f6ded8295f1947b1
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+ *
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+ * LLVM lld cannot do XOR until lld-17.
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+ * https://github.com/llvm/llvm-project/commit/fae96104d4378166cbe5c875ef8ed808a356f3fb
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+ *
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+ * Instead do: (A | B) - (A & B) in order to compute the XOR
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+ * of the two function addresses:
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+ */
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+. = ASSERT(((ABSOLUTE(srso_alias_untrain_ret) | srso_alias_safe_ret) -
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+		(ABSOLUTE(srso_alias_untrain_ret) & srso_alias_safe_ret)) == ((1 << 2) | (1 << 8) | (1 << 14) | (1 << 20)),
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+		"SRSO function pair won't alias");
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+#endif
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+
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 #endif /* CONFIG_X86_32 */
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 #ifdef CONFIG_KEXEC_CORE