[PATCH 4.19 51/52] x86/stackframe: Move ENCODE_FRAME_POINTER to asm/frame.h - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>, Dmitry Safonov <dima@arista.com>
Subject: [PATCH 4.19 51/52] x86/stackframe: Move ENCODE_FRAME_POINTER to asm/frame.h
Date: Thu, 13 Feb 2020 07:21:32 -0800	[thread overview]
Message-ID: <20200213151830.764945877@linuxfoundation.org> (raw)
In-Reply-To: <20200213151810.331796857@linuxfoundation.org>

From: Peter Zijlstra <peterz@infradead.org>

commit a9b3c6998d4a7d53a787cf4d0fd4a4c11239e517 upstream.

In preparation for wider use, move the ENCODE_FRAME_POINTER macros to
a common header and provide inline asm versions.

These macros are used to encode a pt_regs frame for the unwinder; see
unwind_frame.c:decode_frame_pointer().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/entry/calling.h     |   15 -------------
 arch/x86/entry/entry_32.S    |   16 --------------
 arch/x86/include/asm/frame.h |   49 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 31 deletions(-)

--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -172,21 +172,6 @@ For 32-bit we have the following convent
 	.endif
 .endm
 
-/*
- * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
- * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
- * is just setting the LSB, which makes it an invalid stack address and is also
- * a signal to the unwinder that it's a pt_regs pointer in disguise.
- *
- * NOTE: This macro must be used *after* PUSH_AND_CLEAR_REGS because it corrupts
- * the original rbp.
- */
-.macro ENCODE_FRAME_POINTER ptregs_offset=0
-#ifdef CONFIG_FRAME_POINTER
-	leaq 1+\ptregs_offset(%rsp), %rbp
-#endif
-.endm
-
 #ifdef CONFIG_PAGE_TABLE_ISOLATION
 
 /*
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -245,22 +245,6 @@
 .Lend_\@:
 .endm
 
-/*
- * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
- * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
- * is just clearing the MSB, which makes it an invalid stack address and is also
- * a signal to the unwinder that it's a pt_regs pointer in disguise.
- *
- * NOTE: This macro must be used *after* SAVE_ALL because it corrupts the
- * original rbp.
- */
-.macro ENCODE_FRAME_POINTER
-#ifdef CONFIG_FRAME_POINTER
-	mov %esp, %ebp
-	andl $0x7fffffff, %ebp
-#endif
-.endm
-
 .macro RESTORE_INT_REGS
 	popl	%ebx
 	popl	%ecx
--- a/arch/x86/include/asm/frame.h
+++ b/arch/x86/include/asm/frame.h
@@ -22,6 +22,35 @@
 	pop %_ASM_BP
 .endm
 
+#ifdef CONFIG_X86_64
+/*
+ * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
+ * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
+ * is just setting the LSB, which makes it an invalid stack address and is also
+ * a signal to the unwinder that it's a pt_regs pointer in disguise.
+ *
+ * NOTE: This macro must be used *after* PUSH_AND_CLEAR_REGS because it corrupts
+ * the original rbp.
+ */
+.macro ENCODE_FRAME_POINTER ptregs_offset=0
+	leaq 1+\ptregs_offset(%rsp), %rbp
+.endm
+#else /* !CONFIG_X86_64 */
+/*
+ * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
+ * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
+ * is just clearing the MSB, which makes it an invalid stack address and is also
+ * a signal to the unwinder that it's a pt_regs pointer in disguise.
+ *
+ * NOTE: This macro must be used *after* SAVE_ALL because it corrupts the
+ * original ebp.
+ */
+.macro ENCODE_FRAME_POINTER
+	mov %esp, %ebp
+	andl $0x7fffffff, %ebp
+.endm
+#endif /* CONFIG_X86_64 */
+
 #else /* !__ASSEMBLY__ */
 
 #define FRAME_BEGIN				\
@@ -30,12 +59,32 @@
 
 #define FRAME_END "pop %" _ASM_BP "\n"
 
+#ifdef CONFIG_X86_64
+#define ENCODE_FRAME_POINTER			\
+	"lea 1(%rsp), %rbp\n\t"
+#else /* !CONFIG_X86_64 */
+#define ENCODE_FRAME_POINTER			\
+	"movl %esp, %ebp\n\t"			\
+	"andl $0x7fffffff, %ebp\n\t"
+#endif /* CONFIG_X86_64 */
+
 #endif /* __ASSEMBLY__ */
 
 #define FRAME_OFFSET __ASM_SEL(4, 8)
 
 #else /* !CONFIG_FRAME_POINTER */
 
+#ifdef __ASSEMBLY__
+
+.macro ENCODE_FRAME_POINTER ptregs_offset=0
+.endm
+
+#else /* !__ASSEMBLY */
+
+#define ENCODE_FRAME_POINTER
+
+#endif
+
 #define FRAME_BEGIN
 #define FRAME_END
 #define FRAME_OFFSET 0


