CODEWITHSUNDEEP
cassemblyelf
Jay Khandkar
Jay Khandkar

Reputation: 161

Meaning of the value column in the elf symbol table

I have an elf binary which has the following dynsym symbol table as output by readelf:

Num:    Value          Size Type    Bind   Vis      Ndx Name
 0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
 1: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __libc_start_main@GLIBC_2.2.5 (2)
 2: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND __gmon_start__
 3: 0000000000400440     0 FUNC    GLOBAL DEFAULT  UND printf@GLIBC_2.2.5 (2)
 4: 0000000000400460     0 FUNC    GLOBAL DEFAULT  UND fgets@GLIBC_2.2.5 (2)

What does the value column mean? Since this table has 400440 for printf, does that mean that the dynamic linker has to map printf at that address? If yes, how is this value decided? Is it random?

EDIT: Also, this is linux x86-64 with gcc

Upvotes: 2

Views: 1360

Answers (1)

fuz
fuz

Reputation: 93107

It appears that the value of undefined dynamic symbols of function types is just the address of their entry in the PLT. Likewise, the values of entries for variables is probably just their entry in the GOT.

Upvotes: 5

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