linux-kernel - [tip:x86/pti] retpoline: Introduce start/end markers of indirect thunk

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Message-ID: <tip-736e80a4213e9bbce40a7c050337047128b472ac@git.kernel.org>
Date:   Fri, 19 Jan 2018 07:47:22 -0800
From:   tip-bot for Masami Hiramatsu <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        ak@...ux.intel.com, ananth@...ux.vnet.ibm.com, tglx@...utronix.de,
        gregkh@...ux-foundation.org, mingo@...nel.org, hpa@...or.com,
        dwmw@...zon.co.uk, mhiramat@...nel.org, arjan@...ux.intel.com
Subject: [tip:x86/pti] retpoline: Introduce start/end markers of indirect
 thunk

Commit-ID:  736e80a4213e9bbce40a7c050337047128b472ac
Gitweb:     https://git.kernel.org/tip/736e80a4213e9bbce40a7c050337047128b472ac
Author:     Masami Hiramatsu <mhiramat@...nel.org>
AuthorDate: Fri, 19 Jan 2018 01:14:21 +0900
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 19 Jan 2018 16:31:28 +0100

retpoline: Introduce start/end markers of indirect thunk

Introduce start/end markers of __x86_indirect_thunk_* functions.
To make it easy, consolidate .text.__x86.indirect_thunk.* sections
to one .text.__x86.indirect_thunk section and put it in the
end of kernel text section and adds __indirect_thunk_start/end
so that other subsystem (e.g. kprobes) can identify it.

Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: David Woodhouse <dwmw@...zon.co.uk>
Cc: Andi Kleen <ak@...ux.intel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...ux-foundation.org>
Cc: stable@...r.kernel.org
Link: https://lkml.kernel.org/r/151629206178.10241.6828804696410044771.stgit@devbox

---
 arch/x86/include/asm/nospec-branch.h | 3 +++
 arch/x86/kernel/vmlinux.lds.S        | 6 ++++++
 arch/x86/lib/retpoline.S             | 2 +-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 7b45d84..19ba5ad 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -194,6 +194,9 @@ enum spectre_v2_mitigation {
 	SPECTRE_V2_IBRS,
 };
 
+extern char __indirect_thunk_start[];
+extern char __indirect_thunk_end[];
+
 /*
  * On VMEXIT we must ensure that no RSB predictions learned in the guest
  * can be followed in the host, by overwriting the RSB completely. Both
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 1e413a93..9b138a0 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -124,6 +124,12 @@ SECTIONS
 		ASSERT(. - _entry_trampoline == PAGE_SIZE, "entry trampoline is too big");
 #endif
 
+#ifdef CONFIG_RETPOLINE
+		__indirect_thunk_start = .;
+		*(.text.__x86.indirect_thunk)
+		__indirect_thunk_end = .;
+#endif
+
 		/* End of text section */
 		_etext = .;
 	} :text = 0x9090
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S
index cb45c6c..d3415dc 100644
--- a/arch/x86/lib/retpoline.S
+++ b/arch/x86/lib/retpoline.S
@@ -9,7 +9,7 @@
 #include <asm/nospec-branch.h>
 
 .macro THUNK reg
-	.section .text.__x86.indirect_thunk.\reg
+	.section .text.__x86.indirect_thunk
 
 ENTRY(__x86_indirect_thunk_\reg)
 	CFI_STARTPROC