Accessing String Table Indexes for .rodata

Henry C hc128168@gmail.com
Fri Aug 31 11:07:00 GMT 2018


Thanks for replying.

I mean for example,
void myprintf(const char* ptr) {
        printf("%p\n", ptr);
}

int main() {
        myprintf("hello world");
}

Let's say the output is 0x403DE.

Does it mean that Elf64_Shdr::sh_addr of the string table (of .rodata)
+ the offset of "hello word" within the string table is guaranteed to
be the virtual address 0x403DE?  As I am not sure whether virtual
memory addresses of all string literals are defined/calculated when
ELF is created.

Thanks!

Cheers

On Fri, Aug 31, 2018 at 3:54 AM Mark Wielaard <mark@klomp.org> wrote:
>
> On Tue, Aug 21, 2018 at 12:16:09AM +0800, Henry C wrote:
> > Tho, I have no clue how to get the index to each of the string in the
> > string table above.
>
> The .rodata section isn't just a simple ELF string table.
> Otherwise you could use elf_strptr (see libelf.h) to index through them.
> But .rodata also contains other read only data. There is no simple
> ELF based index for just the strings.
>
> > And one more related question is that I noticed the virtual memory
> > addresses of the string literals are same as the offsets to the
> > (executable) file.  Is it intended?  Guaranteed?
>
> If you mean that the sh_offset and sh_addr are the same then that
> not guaranteed. The mapping from file offset to addresses for allocated
> sections is given by the program headers. You can see how they are
> mapped exactly using eu-readelf -l.
>
> Cheers,
>
> Mark



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