extable, core_kernel_data(): Make sure all archs define _sdata

A new utility function (core_kernel_data()) is used to determine if a
passed in address is part of core kernel data or not. It may or may not
return true for RO data, but this utility must work for RW data.

Thus both _sdata and _edata must be defined and continuous,
without .init sections that may later be freed and replaced by
volatile memory (memory that can be freed).

This utility function is used to determine if data is safe from
ever being freed. Thus it should return true for all RW global
data that is not in a module or has been allocated, or false
otherwise.

Also change core_kernel_data() back to the more precise _sdata condition
and document the function.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Acked-by: Hirokazu Takata <takata@linux-m32r.org>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: linux-m68k@lists.linux-m68k.org
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Helge Deller <deller@gmx.de>
Cc: JamesE.J.Bottomley <jejb@parisc-linux.org>
Link: http://lkml.kernel.org/r/1305855298.1465.19.camel@gandalf.stny.rr.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>
----
 arch/alpha/kernel/vmlinux.lds.S   |    1 +
 arch/m32r/kernel/vmlinux.lds.S    |    1 +
 arch/m68k/kernel/vmlinux-std.lds  |    2 ++
 arch/m68k/kernel/vmlinux-sun3.lds |    1 +
 arch/mips/kernel/vmlinux.lds.S    |    1 +
 arch/parisc/kernel/vmlinux.lds.S  |    3 +++
 kernel/extable.c                  |   12 +++++++++++-
 7 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/alpha/kernel/vmlinux.lds.S b/arch/alpha/kernel/vmlinux.lds.S
index 433be2a24f3149261a03600ca19aa6a33992bbc8..3d890a98a08ba139f8d234755512fdb97f0fe51e 100644 (file)
--- a/arch/alpha/kernel/vmlinux.lds.S
+++ b/arch/alpha/kernel/vmlinux.lds.S
@@ -46,6 +46,7 @@ SECTIONS
        __init_end = .;
        /* Freed after init ends here */
 
+       _sdata = .;     /* Start of rw data section */
        _data = .;
        RW_DATA_SECTION(L1_CACHE_BYTES, PAGE_SIZE, THREAD_SIZE)
 

diff --git a/arch/m32r/kernel/vmlinux.lds.S b/arch/m32r/kernel/vmlinux.lds.S
index c194d64cdbb9173912ba2962c4a185561a1e2ad4..cf95aec77460687134d40c0185cd86b95d7aceac 100644 (file)
--- a/arch/m32r/kernel/vmlinux.lds.S
+++ b/arch/m32r/kernel/vmlinux.lds.S
@@ -44,6 +44,7 @@ SECTIONS
   EXCEPTION_TABLE(16)
   NOTES
 
+  _sdata = .;                  /* Start of data section */
   RODATA
   RW_DATA_SECTION(32, PAGE_SIZE, THREAD_SIZE)
   _edata = .;                  /* End of data section */

diff --git a/arch/m68k/kernel/vmlinux-std.lds b/arch/m68k/kernel/vmlinux-std.lds
index 878be5f38cad729d2565c141936978c154ea20b4..d0993594f558b3408317aede57c634c407ea580f 100644 (file)
--- a/arch/m68k/kernel/vmlinux-std.lds
+++ b/arch/m68k/kernel/vmlinux-std.lds
@@ -25,6 +25,8 @@ SECTIONS
 
   EXCEPTION_TABLE(16)
 
+  _sdata = .;                  /* Start of data section */
+
   RODATA
 
   RW_DATA_SECTION(16, PAGE_SIZE, THREAD_SIZE)

diff --git a/arch/m68k/kernel/vmlinux-sun3.lds b/arch/m68k/kernel/vmlinux-sun3.lds
index 1ad6b7ad2c173f36b66f457abb0c19e37deda001..8080469ee6c11c3e86ab59febaa4773790a2ffc7 100644 (file)
--- a/arch/m68k/kernel/vmlinux-sun3.lds
+++ b/arch/m68k/kernel/vmlinux-sun3.lds
@@ -25,6 +25,7 @@ SECTIONS
   _etext = .;                  /* End of text section */
 
   EXCEPTION_TABLE(16) :data
+  _sdata = .;                  /* Start of rw data section */
   RW_DATA_SECTION(16, PAGE_SIZE, THREAD_SIZE) :data
   /* End of data goes *here* so that freeing init code works properly. */
   _edata = .;

diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
index cd2ca544454b1378cb1e831f0f445cc0a2abeea7..01af3876cf90f2e73f684b37a794f8501c800beb 100644 (file)
--- a/arch/mips/kernel/vmlinux.lds.S
+++ b/arch/mips/kernel/vmlinux.lds.S
@@ -65,6 +65,7 @@ SECTIONS
        NOTES :text :note
        .dummy : { *(.dummy) } :text
 
+       _sdata = .;                     /* Start of data section */
        RODATA
 
        /* writeable */

diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S
index 8f1e4efd143e0f32e40ec48a6afb09247b75f0bc..2d9a5c7c76f5142b2d6670a3a8a0b985644be723 100644 (file)
--- a/arch/parisc/kernel/vmlinux.lds.S
+++ b/arch/parisc/kernel/vmlinux.lds.S
@@ -69,6 +69,9 @@ SECTIONS
        /* End of text section */
        _etext = .;
 
+       /* Start of data section */
+       _sdata = .;
+
        RODATA
 
        /* writeable */

diff --git a/kernel/extable.c b/kernel/extable.c
index d44aac0c3faa06b05e49005b9e31d843e2c7481e..5339705b82410515dcadce220ef997930dd3247c 100644 (file)
--- a/kernel/extable.c
+++ b/kernel/extable.c
@@ -72,9 +72,19 @@ int core_kernel_text(unsigned long addr)
        return 0;
 }
 
+/**
+ * core_kernel_data - tell if addr points to kernel data
+ * @addr: address to test
+ *
+ * Returns true if @addr passed in is from the core kernel data
+ * section.
+ *
+ * Note: On some archs it may return true for core RODATA, and false
+ *  for others. But will always be true for core RW data.
+ */
 int core_kernel_data(unsigned long addr)
 {
-       if (addr >= (unsigned long)_stext &&
+       if (addr >= (unsigned long)_sdata &&
            addr < (unsigned long)_edata)
                return 1;
        return 0;