linux-kernel - [PATCH] module: set ksymtab/kcrctab* section addresses to 0x0

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Date:	Mon, 26 Jan 2015 21:45:55 +0100
From:	Rabin Vincent <rabin.vincent@...s.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	linux-kernel@...r.kernel.org, Rabin Vincent <rabinv@...s.com>
Subject: [PATCH] module: set ksymtab/kcrctab* section addresses to 0x0

These __ksymtab*/__kcrctab* sections currently have non-zero addresses.
Non-zero section addresses in a relocatable ELF confuse GDB and it ends
up not relocating all symbols when add-symbol-file is used on modules
which have exports.  The kernel's module loader does not care about
these addresses, so let's just set them to zero.

 Before:

  $ readelf -S lib/notifier-error-inject.ko   | grep 'Name\| __ksymtab_gpl'
    [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
    [ 8] __ksymtab_gpl     PROGBITS        0000000c 0001b4 000010 00   A  0   0  4

  (gdb) add-symbol-file lib/notifier-error-inject.ko 0x500000 -s .bss 0x700000
  add symbol table from file "lib/notifier-error-inject.ko" at
     .text_addr = 0x500000
     .bss_addr = 0x700000
  (gdb) p &notifier_err_inject_dir
  $3 = (struct dentry **) 0x0

 After:

  $ readelf -S lib/notifier-error-inject.ko   | grep 'Name\| __ksymtab_gpl'
    [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al
    [ 8] __ksymtab_gpl     PROGBITS        00000000 0001b4 000010 00   A  0   0  4

  (gdb) add-symbol-file lib/notifier-error-inject.ko 0x500000 -s .bss 0x700000
  add symbol table from file "lib/notifier-error-inject.ko" at
     .text_addr = 0x500000
     .bss_addr = 0x700000
  (gdb) p &notifier_err_inject_dir
  $3 = (struct dentry **) 0x700000

Signed-off-by: Rabin Vincent <rabin.vincent@...s.com>
---
 scripts/module-common.lds |   20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/scripts/module-common.lds b/scripts/module-common.lds
index 0865b3e..bec15f9 100644
--- a/scripts/module-common.lds
+++ b/scripts/module-common.lds
@@ -6,14 +6,14 @@
 SECTIONS {
 	/DISCARD/ : { *(.discard) }
 
-	__ksymtab		: { *(SORT(___ksymtab+*)) }
-	__ksymtab_gpl		: { *(SORT(___ksymtab_gpl+*)) }
-	__ksymtab_unused	: { *(SORT(___ksymtab_unused+*)) }
-	__ksymtab_unused_gpl	: { *(SORT(___ksymtab_unused_gpl+*)) }
-	__ksymtab_gpl_future	: { *(SORT(___ksymtab_gpl_future+*)) }
-	__kcrctab		: { *(SORT(___kcrctab+*)) }
-	__kcrctab_gpl		: { *(SORT(___kcrctab_gpl+*)) }
-	__kcrctab_unused	: { *(SORT(___kcrctab_unused+*)) }
-	__kcrctab_unused_gpl	: { *(SORT(___kcrctab_unused_gpl+*)) }
-	__kcrctab_gpl_future	: { *(SORT(___kcrctab_gpl_future+*)) }
+	__ksymtab		0 : { *(SORT(___ksymtab+*)) }
+	__ksymtab_gpl		0 : { *(SORT(___ksymtab_gpl+*)) }
+	__ksymtab_unused	0 : { *(SORT(___ksymtab_unused+*)) }
+	__ksymtab_unused_gpl	0 : { *(SORT(___ksymtab_unused_gpl+*)) }
+	__ksymtab_gpl_future	0 : { *(SORT(___ksymtab_gpl_future+*)) }
+	__kcrctab		0 : { *(SORT(___kcrctab+*)) }
+	__kcrctab_gpl		0 : { *(SORT(___kcrctab_gpl+*)) }
+	__kcrctab_unused	0 : { *(SORT(___kcrctab_unused+*)) }
+	__kcrctab_unused_gpl	0 : { *(SORT(___kcrctab_unused_gpl+*)) }
+	__kcrctab_gpl_future	0 : { *(SORT(___kcrctab_gpl_future+*)) }
 }
-- 
1.7.10.4

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