[PATCH] relocatable kernel: Kallsyms generate relocatable symbols

Print the addresses of non-absolute symbols relative to _text
so that ld will generate relocations.  Allowing a relocatable
kernel to relocate them.  We can't actually use the symbol names
because kallsyms includes static symbols that are not exported
from their object files.

Add the _text symbol definitions to the architectures which don't
define it otherwise linker will fail.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andi Kleen <ak@suse.de>

8 files changed, 24 insertions, 3 deletions

diff --git a/arch/h8300/kernel/vmlinux.lds.S b/arch/h8300/kernel/vmlinux.lds.S
index 756325dd480e..f05288be8878 100644
--- a/arch/h8300/kernel/vmlinux.lds.S
+++ b/arch/h8300/kernel/vmlinux.lds.S
@@ -70,6 +70,7 @@ SECTIONS
 #endif
         .text :
         {
+        _text = .;
 #if defined(CONFIG_ROMKERNEL)
         *(.int_redirect)
 #endif
diff --git a/arch/m68knommu/kernel/vmlinux.lds.S b/arch/m68knommu/kernel/vmlinux.lds.S
index 58afa8be604e..2b2a10da64a4 100644
--- a/arch/m68knommu/kernel/vmlinux.lds.S
+++ b/arch/m68knommu/kernel/vmlinux.lds.S
@@ -60,6 +60,7 @@ SECTIONS {
 #endif
 
         .text : {
+                _text = .;
                 _stext = . ;
                 *(.text)
                 SCHED_TEXT
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index e8342d867536..04b98671a060 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S
@@ -33,6 +33,7 @@ SECTIONS
 
         /* Text and gots */
         .text : {
+                _text = .;
                 *(.text .text.*)
                 SCHED_TEXT
                 LOCK_TEXT
diff --git a/arch/ppc/kernel/vmlinux.lds.S b/arch/ppc/kernel/vmlinux.lds.S
index 16e8661e1fec..61921268a0d0 100644
--- a/arch/ppc/kernel/vmlinux.lds.S
+++ b/arch/ppc/kernel/vmlinux.lds.S
@@ -31,6 +31,7 @@ SECTIONS
   .plt : { *(.plt) }
   .text      :
   {
+    _text = .;
     *(.text)
     SCHED_TEXT
     LOCK_TEXT
diff --git a/arch/sparc/kernel/vmlinux.lds.S b/arch/sparc/kernel/vmlinux.lds.S
index 5cc5ff7f8824..b73e6b9067ed 100644
--- a/arch/sparc/kernel/vmlinux.lds.S
+++ b/arch/sparc/kernel/vmlinux.lds.S
@@ -11,6 +11,7 @@ SECTIONS
   . = 0x10000 + SIZEOF_HEADERS;
   .text 0xf0004000 :
   {
+    _text = .;
     *(.text)
     SCHED_TEXT
     LOCK_TEXT
diff --git a/arch/sparc64/kernel/vmlinux.lds.S b/arch/sparc64/kernel/vmlinux.lds.S
index bd9de8c2a2aa..4a6063f33e7a 100644
--- a/arch/sparc64/kernel/vmlinux.lds.S
+++ b/arch/sparc64/kernel/vmlinux.lds.S
@@ -13,6 +13,7 @@ SECTIONS
   . = 0x4000;
   .text 0x0000000000404000 :
   {
+    _text = .;
     *(.text)
     SCHED_TEXT
     LOCK_TEXT
diff --git a/arch/v850/kernel/vmlinux.lds.S b/arch/v850/kernel/vmlinux.lds.S
index 88d087f527c9..3a5fd07fe064 100644
--- a/arch/v850/kernel/vmlinux.lds.S
+++ b/arch/v850/kernel/vmlinux.lds.S
@@ -90,6 +90,7 @@
 
 /* Kernel text segment, and some constant data areas.  */
 #define TEXT_CONTENTS                                                         \
+                _text = .;                                                    \
                 __stext = . ;                                                 \
                 *(.text)                                                      \
                 SCHED_TEXT                                                    \
diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 22d281c6ec24..4c1ad0acbb4b 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -43,7 +43,7 @@ struct sym_entry {
 
 static struct sym_entry *table;
 static unsigned int table_size, table_cnt;
-static unsigned long long _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext;
+static unsigned long long _text, _stext, _etext, _sinittext, _einittext, _sextratext, _eextratext;
 static int all_symbols = 0;
 static char symbol_prefix_char = '\0';
 
@@ -91,7 +91,9 @@ static int read_symbol(FILE *in, struct sym_entry *s)
                 sym++;
 
         /* Ignore most absolute/undefined (?) symbols. */
-        if (strcmp(sym, "_stext") == 0)
+        if (strcmp(sym, "_text") == 0)
+                _text = s->addr;
+        else if (strcmp(sym, "_stext") == 0)
                 _stext = s->addr;
         else if (strcmp(sym, "_etext") == 0)
                 _etext = s->addr;
@@ -265,9 +267,21 @@ static void write_src(void)
 
         printf(".data\n");
 
+        /* Provide proper symbols relocatability by their '_text'
+         * relativeness.  The symbol names cannot be used to construct
+         * normal symbol references as the list of symbols contains
+         * symbols that are declared static and are private to their
+         * .o files.  This prevents .tmp_kallsyms.o or any other
+         * object from referencing them.
+         */
         output_label("kallsyms_addresses");
         for (i = 0; i < table_cnt; i++) {
-                printf("\tPTR\t%#llx\n", table[i].addr);
+                if (toupper(table[i].sym[0]) != 'A') {
+                        printf("\tPTR\t_text + %#llx\n",
+                                table[i].addr - _text);
+                } else {
+                        printf("\tPTR\t%#llx\n", table[i].addr);
+                }
         }
         printf("\n");