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 Post subject: 如何將內建library的function固定在某些section裡
PostPosted: Wed Mar 13, 2013 2:59 pm 
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Joined: Fri Mar 04, 2011 9:36 pm
Posts: 500
自己寫的程式,如果想訂在某個section上,
可以用下面的語法。
viewtopic.php?f=16&t=132

但是對於library,例如memcpy等function,不能用這個方法。
因為它在編譯時即指定好section。
所以我們要知道function所屬的section或是所屬的.o檔案。
------------------------------------------------------------------
library在這邊

nds32le-elf/libc/newlib/usr/lib/libc.a

用readelf -Ss 看section和symbol的話,
(即為readelf -Ss libc.a)
可以看出 memcpy和abs是有function sections的,
(strcpy沒有)

File: ./libc.a(lib_a-abs.o)

[ 8] .text.memcpy PROGBITS 00000000 000618 000088 00 AX 0 0 4

8: 00000000 136 FUNC GLOBAL DEFAULT 8 memcpy



File: ./libc.a(lib_a-strcpy.o)

[ 1] .text PROGBITS 00000000 000034 00003c 00 AX 0 0 4

5: 00000000 60 FUNC GLOBAL DEFAULT 1 strcpy



File: ./libc.a(lib_a-memcpy.o)

[ 8] .text.abs PROGBITS 00000000 000614 000008 00 AX 0 0 4

8: 00000000 8 FUNC GLOBAL DEFAULT 8 abs


有section的, 可以用 * (.text.memcpy) 來拉

---------------------------------------------------------------------
如果是mculib的話, 因為本來就是分檔寫的, 所以沒有刻意寫成不同section,

newlib是標準的C code, 才有用-ffunction-sections分隔



File: libc.a(lib_a-memcpy.o)

There are 11 section headers, starting at offset 0x12c:



Section Headers:

[Nr] Name Type Addr Off Size ES Flg Lk Inf Al

[ 0] NULL 00000000 000000 000000 00 0 0 0

[ 1] .text PROGBITS 00000000 000034 000088 00 AX 0 0 4 <-- section 1 是.text

[ 2] .rela.text RELA 00000000 00035c 0000a8 0c 9 1 4

[ 3] .rel.text REL 00000000 000404 000000 08 9 1 4

[ 4] .data PROGBITS 00000000 0000bc 000000 00 WA 0 0 1

[ 5] .bss NOBITS 00000000 0000bc 000000 00 WA 0 0 1

[ 6] .mdebug.abi_nds32 PROGBITS 00000000 0000bc 000000 00 0 0 1

[ 7] .comment PROGBITS 00000000 0000bc 000019 00 0 0 1

[ 8] .shstrtab STRTAB 00000000 0000d5 000056 00 0 0 1

[ 9] .symtab SYMTAB 00000000 0002e4 000070 10 10 6 4

[10] .strtab STRTAB 00000000 000354 000008 00 0 0 1

Key to Flags:

W (write), A (alloc), X (execute), M (merge), S (strings)

I (info), L (link order), G (group), x (unknown)

O (extra OS processing required) o (OS specific), p (processor specific)



Symbol table '.symtab' contains 7 entries:

Num: Value Size Type Bind Vis Ndx Name

0: 00000000 0 NOTYPE LOCAL DEFAULT UND

1: 00000000 0 SECTION LOCAL DEFAULT 1

2: 00000000 0 SECTION LOCAL DEFAULT 4

3: 00000000 0 SECTION LOCAL DEFAULT 5

4: 00000000 0 SECTION LOCAL DEFAULT 6

5: 00000000 0 SECTION LOCAL DEFAULT 7

6: 00000000 136 FUNC GLOBAL DEFAULT 1 memcpy <-- 在 section 1



--------------------------------------------------------------------
.text : {

*libc.a:*memcpy.o (.text .text.*)

* (.text .text.*)

}



主要是只寫 libc.a 不夠, 因為他前面應該會有path,

所以使用 * 來match pattern

另外, 為了避免library內有修改檔名或section名,

建議後面也都用 wildcard pattern.



另外要注意, 先符合會先拉, 所以要注意順序.

例如這樣不行, 因為會被 * 先拉完

.text : {

* (.text .text.*)

*libc.a:*memcpy.o (.text .text.*)

}



http://sourceware.org/binutils/docs-2.2 ... -Wildcards

``a file name matches more than one wildcard pattern,

or if a file name appears explicitly and is also matched by a wildcard pattern,

the linker will use the first match in the linker script.''




--------------------------------------------------------------
注意!比較新的compiler才有分成各section或是分檔寫。
附件是一個example。


Attachments:
linker.zip [38.49 KiB]
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 Post subject: Re: 如何將內建library的function固定在某些section裡
PostPosted: Wed May 07, 2014 10:48 am 
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Joined: Wed Apr 13, 2011 7:44 pm
Posts: 23
Attachment:
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如附件”demo-printf.zip”的demo。
它將libc.a中的*printf.o跟*atoi.o放到特定的section0中。
先在nds32.sag中新增section0,
使用Linker script generation "nds_ldsag.exe" utility 產生nds32.ld檔案後,
手動修改nds32.ld檔,將*printf.o跟*atoi.o放到section0中。
Code:
     .text         :    {
         *(EXCLUDE_FILE (*libc.a:*atoi.o) .text
         .stub
         EXCLUDE_FILE (*libc.a:*printf.o) .text.*
         .gnu.linkonce.t.*) KEEP(*(.text.*personality*)) *(.gnu.warning) . = ALIGN(4); }
     ………………
     .section0         :    AT(LOADADDR (.bss) + SIZEOF (.bss))
         {
              *libc.a:*printf.o (.text .text.*) *atoi.o
              *(.section0) }


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