>
quoted text
> layout_section() called this:
>
> static long get_offset(unsigned long *size, Elf_Shdr *sechdr)
> {
>         long ret;
>
>         ret = ALIGN(*size, sechdr->sh_addralign ?: 1);
>         *size = ret + sechdr->sh_size;
>         return ret;
> }
>
> From header:
>
> typedef struct {
>   Elf32_Word    sh_name;
>   Elf32_Word    sh_type;
>   Elf32_Word    sh_flags;
>   Elf32_Addr    sh_addr;
>   Elf32_Off     sh_offset;
>   Elf32_Word    sh_size;
>   Elf32_Word    sh_link;
>   Elf32_Word    sh_info;
>   Elf32_Word    sh_addralign;
>   Elf32_Word    sh_entsize;
> } Elf32_Shdr;
>
> typedef struct elf64_shdr {
>   Elf64_Word sh_name;           /* Section name, index in string tbl */
>   Elf64_Word sh_type;           /* Type of section */
>   Elf64_Xword sh_flags;         /* Miscellaneous section attributes */
>   Elf64_Addr sh_addr;           /* Section virtual addr at execution */
>   Elf64_Off sh_offset;          /* Section file offset */
>   Elf64_Xword sh_size;          /* Size of section in bytes */
>   Elf64_Word sh_link;           /* Index of another section */
>   Elf64_Word sh_info;           /* Additional section information */
>   Elf64_Xword sh_addralign;     /* Section alignment */
>   Elf64_Xword sh_entsize;       /* Entry size if section holds table */
> } Elf64_Shdr;
>
> Which I think is responsible for the alignment of the section in memory.
>
> Two thing:   memory offset and file offset - u have to distinguish
> between the two.   fileoffset no alignment, but memory yes.   So in
> loading process, some empty spaces have to inserted.
>
>  sechdr->sh_size==> this is physical file offset (from byte 0 of the file).
> ret --> ****I THINK**** is trying to round up the current *size value
> to the next alignment value, and then add this
>


Thanks, Peter for the wonderful explanation.

I was curious how I would find the start and end of a section in
memory of ".data" section. From the code, I believe it is
sechdr->sh_addr (start). How to reach the end(in memory) since  the
field  sechdr->sh_size is physical as per your explanation?


Regards,
Asim

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