jump label: Base patch for jump label

base patch to implement 'jump labeling'. Based on a new 'asm goto' inline
assembly gcc mechanism, we can now branch to labels from an 'asm goto'
statment. This allows us to create a 'no-op' fastpath, which can subsequently
be patched with a jump to the slowpath code. This is useful for code which
might be rarely used, but which we'd like to be able to call, if needed.
Tracepoints are the current usecase that these are being implemented for.

Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <ee8b3595967989fdaf84e698dc7447d315ce972a.1284733808.git.jbaron@redhat.com>

[ cleaned up some formating ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 8a92a170fb7d..ef2af9948eac 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -220,6 +220,8 @@
                                                                         \
         BUG_TABLE                                                       \
                                                                         \
+        JUMP_TABLE                                                      \
+                                                                        \
         /* PCI quirks */                                                \
         .pci_fixup        : AT(ADDR(.pci_fixup) - LOAD_OFFSET) {        \
                 VMLINUX_SYMBOL(__start_pci_fixups_early) = .;           \
@@ -563,6 +565,14 @@
 #define BUG_TABLE
 #endif
 
+#define JUMP_TABLE                                                      \
+        . = ALIGN(8);                                                   \
+        __jump_table : AT(ADDR(__jump_table) - LOAD_OFFSET) {           \
+                VMLINUX_SYMBOL(__start___jump_table) = .;               \
+                *(__jump_table)                                         \
+                VMLINUX_SYMBOL(__stop___jump_table) = .;                \
+        }
+
 #ifdef CONFIG_PM_TRACE
 #define TRACEDATA                                                       \
         . = ALIGN(4);                                                   \