x86, trampoline: Common infrastructure for low memory trampolines

Common infrastructure for low memory trampolines.  This code installs
the trampolines permanently in low memory very early.  It also permits
multiple pieces of code to be used for this purpose.

This code also introduces a standard infrastructure for computing
symbol addresses in the trampoline code.

The only change to the actual SMP trampolines themselves is that the
64-bit trampoline has been made reusable -- the previous version would
overwrite the code with a status variable; this moves the status
variable to a separate location.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
LKML-Reference: <4D5DFBE4.7090104@intel.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Matthieu Castet <castet.matthieu@free.fr>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index bf4700755184..cb2c5069b016 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -240,6 +240,18 @@ SECTIONS
 
         INIT_DATA_SECTION(16)
 
+        /*
+         * Code and data for a variety of lowlevel trampolines, to be
+         * copied into base memory (< 1 MiB) during initialization.
+         * Since it is copied early, the main copy can be discarded
+         * afterwards.
+         */
+         .x86_trampoline : AT(ADDR(.x86_trampoline) - LOAD_OFFSET) {
+                x86_trampoline_start = .;
+                *(.x86_trampoline)
+                x86_trampoline_end = .;
+        }
+
         .x86_cpu_dev.init : AT(ADDR(.x86_cpu_dev.init) - LOAD_OFFSET) {
                 __x86_cpu_dev_start = .;
                 *(.x86_cpu_dev.init)
@@ -291,6 +303,7 @@ SECTIONS
                 *(.iommu_table)
                 __iommu_table_end = .;
         }
+
         . = ALIGN(8);
         /*
          * .exit.text is discard at runtime, not link time, to deal with