[PATCH] x86-64: Speed up dwarf2 unwinder
This changes the dwarf2 unwinder to do a binary search for CIEs
instead of a linear work. The linker is unfortunately not
able to build a proper lookup table at link time, instead it creates
one at runtime as soon as the bootmem allocator is usable (so you'll continue
using the linear lookup for the first [hopefully] few calls).
The code should be ready to utilize a build-time created table once
a fixed linker becomes available.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 69240b5..9d0d11c 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -125,6 +125,10 @@
*(__param) \
VMLINUX_SYMBOL(__stop___param) = .; \
} \
+ \
+ /* Unwind data binary search table */ \
+ EH_FRAME_HDR \
+ \
__end_rodata = .; \
. = ALIGN(4096);
@@ -157,6 +161,18 @@
*(.kprobes.text) \
VMLINUX_SYMBOL(__kprobes_text_end) = .;
+#ifdef CONFIG_STACK_UNWIND
+ /* Unwind data binary search table */
+#define EH_FRAME_HDR \
+ .eh_frame_hdr : AT(ADDR(.eh_frame_hdr) - LOAD_OFFSET) { \
+ VMLINUX_SYMBOL(__start_unwind_hdr) = .; \
+ *(.eh_frame_hdr) \
+ VMLINUX_SYMBOL(__end_unwind_hdr) = .; \
+ }
+#else
+#define EH_FRAME_HDR
+#endif
+
/* DWARF debug sections.
Symbols in the DWARF debugging sections are relative to
the beginning of the section so we begin them at 0. */