getting text strings into __initdata for char *foo = "data"

getting text strings into __initdata for char *foo = "data"

[Patrick Mansfield]

Hi -

Is there a way to get char * initialized data to go into the init
data section?

For example, in the following I want init_foobar and its associated
text strings to go into the init data section, not just the pointers
in init_foobar:

[patman@elm3a50 bleed-2.5]$ more initdata.c
#include <linux/init.h>

/*
 * This only puts the pointer in .init.data.
 */
char *init_foobar[] __initdata = { 
        "AAAAtextAAAAtextAAAAtext-morea",
        "AAAA",
        "AAAA",
};

/*
 * Following is OK, but wastes some space (on disk) and needs one extra byte
 * for the '\0'. Worse, the second entry below is not '\0' terminated and gets
 * no compilation warning :(
 */
char init_foobar2[][31] __initdata = { 
        "BBBBtextBBBBtextBBBBtext-morea",
        "BBBBtextBBBBtextBBBBtext-morebc",
        "BBBB",
        "BBBB",
};

char *regular_foobar[] = {
        "CCCCtextCCCCtextCCCCtext-morea",
        "CCCCtextCCCCtextCCCCtext-moreb",
        "CCCC",
};


[patman@elm3a50 bleed-2.5]$ objdump -s initdata.o 

initdata.o:     file format elf32-i386

Contents of section .text:
Contents of section .data:
 0000 40000000 20000000 05000000           @... .......    
Contents of section .note:
 0000 08000000 00000000 01000000 30312e30  ............01.0
 0010 31000000                             1...            
Contents of section .init.data:
 0000 00000000 00000000 00000000 42424242  ............BBBB
 0010 74657874 42424242 74657874 42424242  textBBBBtextBBBB
 0020 74657874 2d6d6f72 65610042 42424274  text-morea.BBBBt
 0030 65787442 42424274 65787442 42424274  extBBBBtextBBBBt
 0040 6578742d 6d6f7265 62634242 42420000  ext-morebcBBBB..
 0050 00000000 00000000 00000000 00000000  ................
 0060 00000000 00000000 00424242 42000000  .........BBBB...
 0070 00000000 00000000 00000000 00000000  ................
 0080 00000000 00000000                    ........        
Contents of section .rodata.str1.1:
 0000 41414141 00434343 4300               AAAA.CCCC.      
Contents of section .rodata.str1.32:
 0000 41414141 74657874 41414141 74657874  AAAAtextAAAAtext
 0010 41414141 74657874 2d6d6f72 65610000  AAAAtext-morea..
 0020 43434343 74657874 43434343 74657874  CCCCtextCCCCtext
 0030 43434343 74657874 2d6d6f72 65620000  CCCCtext-moreb..
 0040 43434343 74657874 43434343 74657874  CCCCtextCCCCtext
 0050 43434343 74657874 2d6d6f72 656100    CCCCtext-morea. 
Contents of section .comment:
 0000 00474343 3a202847 4e552920 322e3936  .GCC: (GNU) 2.96
 0010 20323030 30303733 31202852 65642048   20000731 (Red H
 0020 6174204c 696e7578 20372e31 20322e39  at Linux 7.1 2.9
 0030 362d3938 2900                        6-98).          


-- Patrick Mansfield

Re: getting text strings into __initdata for char *foo = "data"

[Richard B. Johnson]

On Wed, 20 Nov 2002, Patrick Mansfield wrote:

> Hi -
> 
> Is there a way to get char * initialized data to go into the init
> data section?
> 
> For example, in the following I want init_foobar and its associated
> text strings to go into the init data section, not just the pointers
> in init_foobar:
> 

[SNIPPED...]




I use assembler when I need to do things 'C' doesn't want
to do.. like:

.section .init.data
.global foo
.type foo,@object
.size foo,11
foo: .string	"1234567890"

This will work for ".sections" like .data, etc,. but the
object file in empty when I use .init.data. This is probably
because gas treats .string specially. I know you can do this
with ".byte". You don't have to make the assembly by hand.

I do something like:

#ifdef THIS_WILL_NEVER_BE_DEFINED
char foo[]="This is the string..."
#else
extern char foo[];
#endif

I write a 'C' program that looks for "THIS_WILL_NEVER_BE_DEFINED"
and writes gas assembly for the strings up to the "#else".

I do this in an embedded system to put many/most/all strings
in NVRAM PROM.


Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
   Bush : The Fourth Reich of America

Re: getting text strings into __initdata for char *foo = "data"

[Keith Owens]

On Wed, 20 Nov 2002 14:43:43 -0800, 
Patrick Mansfield <patmans@us.ibm.com> wrote:
>Is there a way to get char * initialized data to go into the init
>data section?
>
>For example, in the following I want init_foobar and its associated
>text strings to go into the init data section, not just the pointers
>in init_foobar:

>From the kdb common patch, kdb/Makefile.

gen-kdb_cmds.c: kdb_cmds Makefile
	$(AWK) 'BEGIN {print "#include <linux/init.h>"} \
		/^ *#/{next} \
		/^[ \t]*$$/{next} \
		{gsub(/"/, "\\\"", $$0); \
		  print "static __initdata char kdb_cmd" cmds++ "[] = \"" $$0 "\\n\";"} \
		END {print "char __initdata *kdb_cmds[] = {"; for (i = 0; i < cmds; ++i) {print "  kdb_cmd" i ","}; print("  0\n};");}' \
		kdb_cmds > gen-kdb_cmds.c

Converts kdb_cmds

set LINES 2000
set BTSP 1
bp sys_open

into gen-kdb_cmds.c

#include <linux/init.h>
static __initdata char kdb_cmd0[] = "set LINES 2000\n";
static __initdata char kdb_cmd1[] = "set BTSP 1\n";
static __initdata char kdb_cmd2[] = "bp sys_open\n";
char __initdata *kdb_cmds[] = {
  kdb_cmd0,
  kdb_cmd1,
  kdb_cmd2,
  0
};

# objdump -h kdb/gen-kdb_cmds.o

kdb/gen-kdb_cmds.o:     file format elf64-ia64-little

Sections:
Idx Name          Size      VMA               LMA               File off  Algn
  0 .text         00000000  0000000000000000  0000000000000000  00000040  2**4
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  1 .data         00000000  0000000000000000  0000000000000000  00000040  2**0
                  CONTENTS, ALLOC, LOAD, DATA
  2 .bss          00000000  0000000000000000  0000000000000000  00000040  2**0
                  ALLOC
  3 .debug_abbrev 000000a8  0000000000000000  0000000000000000  00000040  2**0
                  CONTENTS, READONLY, DEBUGGING
  4 .debug_info   000001c7  0000000000000000  0000000000000000  000000e8  2**0
                  CONTENTS, RELOC, READONLY, DEBUGGING
  5 .debug_line   00000000  0000000000000000  0000000000000000  000002af  2**0
                  CONTENTS, READONLY, DEBUGGING
  6 .data.init    00000050  0000000000000000  0000000000000000  000002b0  2**3
                  CONTENTS, ALLOC, LOAD, RELOC, DATA
  7 .debug_pubnames 0000001f  0000000000000000  0000000000000000  00000300  2**0
                  CONTENTS, RELOC, READONLY, DEBUGGING
  8 .comment      00000029  0000000000000000  0000000000000000  0000031f  2**0
                  CONTENTS, READONLY

text, data and bss are all 0 size.  Everything is in .data.init.