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-rw-r--r--arch/x86/include/asm/frame.h49
1 files changed, 49 insertions, 0 deletions
diff --git a/arch/x86/include/asm/frame.h b/arch/x86/include/asm/frame.h
index 5cbce6fbb534..296b346184b2 100644
--- 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