x86-64: Handle PC-relative relocations on per-CPU data

This is in preparation of using RIP-relative addressing in many of the
per-CPU accesses.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Link: http://lkml.kernel.org/r/5458A15A0200007800044A9A@mail.emea.novell.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 40 insertions, 10 deletions

diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 57ab74df7eea..644abd767c12 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -260,7 +260,7 @@ static void handle_relocations(void *output, unsigned long output_len)
 
         /*
          * Process relocations: 32 bit relocations first then 64 bit after.
-         * Two sets of binary relocations are added to the end of the kernel
+         * Three sets of binary relocations are added to the end of the kernel
          * before compression. Each relocation table entry is the kernel
          * address of the location which needs to be updated stored as a
          * 32-bit value which is sign extended to 64 bits.
@@ -270,6 +270,8 @@ static void handle_relocations(void *output, unsigned long output_len)
          * kernel bits...
          * 0 - zero terminator for 64 bit relocations
          * 64 bit relocation repeated
+         * 0 - zero terminator for inverse 32 bit relocations
+         * 32 bit inverse relocation repeated
          * 0 - zero terminator for 32 bit relocations
          * 32 bit relocation repeated
          *
@@ -286,6 +288,16 @@ static void handle_relocations(void *output, unsigned long output_len)
                 *(uint32_t *)ptr += delta;
         }
 #ifdef CONFIG_X86_64
+        while (*--reloc) {
+                long extended = *reloc;
+                extended += map;
+
+                ptr = (unsigned long)extended;
+                if (ptr < min_addr || ptr > max_addr)
+                        error("inverse 32-bit relocation outside of kernel!\n");
+
+                *(int32_t *)ptr -= delta;
+        }
         for (reloc--; *reloc; reloc--) {
                 long extended = *reloc;
                 extended += map;
diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index a5efb21d5228..0c2fae8d929d 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -20,7 +20,10 @@ struct relocs {
 
 static struct relocs relocs16;
 static struct relocs relocs32;
+#if ELF_BITS == 64
+static struct relocs relocs32neg;
 static struct relocs relocs64;
+#endif
 
 struct section {
         Elf_Shdr       shdr;
@@ -762,11 +765,16 @@ static int do_reloc64(struct section *sec, Elf_Rel *rel, ElfW(Sym) *sym,
 
         switch (r_type) {
         case R_X86_64_NONE:
+                /* NONE can be ignored. */
+                break;
+
         case R_X86_64_PC32:
                 /*
-                 * NONE can be ignored and PC relative relocations don't
-                 * need to be adjusted.
+                 * PC relative relocations don't need to be adjusted unless
+                 * referencing a percpu symbol.
                  */
+                if (is_percpu_sym(sym, symname))
+                        add_reloc(&relocs32neg, offset);
                 break;
 
         case R_X86_64_32:
@@ -986,7 +994,10 @@ static void emit_relocs(int as_text, int use_real_mode)
         /* Order the relocations for more efficient processing */
         sort_relocs(&relocs16);
         sort_relocs(&relocs32);
+#if ELF_BITS == 64
+        sort_relocs(&relocs32neg);
         sort_relocs(&relocs64);
+#endif
 
         /* Print the relocations */
         if (as_text) {
@@ -1007,14 +1018,21 @@ static void emit_relocs(int as_text, int use_real_mode)
                 for (i = 0; i < relocs32.count; i++)
                         write_reloc(relocs32.offset[i], stdout);
         } else {
-                if (ELF_BITS == 64) {
-                        /* Print a stop */
-                        write_reloc(0, stdout);
+#if ELF_BITS == 64
+                /* Print a stop */
+                write_reloc(0, stdout);
 
-                        /* Now print each relocation */
-                        for (i = 0; i < relocs64.count; i++)
-                                write_reloc(relocs64.offset[i], stdout);
-                }
+                /* Now print each relocation */
+                for (i = 0; i < relocs64.count; i++)
+                        write_reloc(relocs64.offset[i], stdout);
+
+                /* Print a stop */
+                write_reloc(0, stdout);
+
+                /* Now print each inverse 32-bit relocation */
+                for (i = 0; i < relocs32neg.count; i++)
+                        write_reloc(relocs32neg.offset[i], stdout);
+#endif
 
                 /* Print a stop */
                 write_reloc(0, stdout);