Why does the address of an internal symbol needs to be recorded in .got?
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I am reading the blog https://eli.thegreenplace.net/2011/11/11/position-independent-code-pic-in-shared-libraries-on-x64
In the part "x64 PIC with data references - an example", it seems that the module is telling the dynamic linker to fill the absolute address of myglob into .got, then the code get that address and read data from that address.
But why does the compiler have to do this, it's a symbol come from itself, why can't just use RIP-relative addressing to access this symbol? Is it because sometimes .data of the module might be load to a unknown offset to .text(instead of always loaded next to .text)?
I mean, if address_of(myglob)-address_of(instruction_that_access_myglob) is a certain value, why do we even have to know the absolute address of myglob?
linux dynamic-linking x86 dynamic-loading
asked Feb 14 at 2:15
炸鱼薯条德里克炸鱼薯条德里克
5311215
add a comment |
I am reading the blog https://eli.thegreenplace.net/2011/11/11/position-independent-code-pic-in-shared-libraries-on-x64
In the part "x64 PIC with data references - an example", it seems that the module is telling the dynamic linker to fill the absolute address of myglob into .got, then the code get that address and read data from that address.
But why does the compiler have to do this, it's a symbol come from itself, why can't just use RIP-relative addressing to access this symbol? Is it because sometimes .data of the module might be load to a unknown offset to .text(instead of always loaded next to .text)?
I mean, if address_of(myglob)-address_of(instruction_that_access_myglob) is a certain value, why do we even have to know the absolute address of myglob?
linux dynamic-linking x86 dynamic-loading
asked Feb 14 at 2:15
炸鱼薯条德里克炸鱼薯条德里克
5311215
add a comment |
I am reading the blog https://eli.thegreenplace.net/2011/11/11/position-independent-code-pic-in-shared-libraries-on-x64
In the part "x64 PIC with data references - an example", it seems that the module is telling the dynamic linker to fill the absolute address of myglob into .got, then the code get that address and read data from that address.
But why does the compiler have to do this, it's a symbol come from itself, why can't just use RIP-relative addressing to access this symbol? Is it because sometimes .data of the module might be load to a unknown offset to .text(instead of always loaded next to .text)?
I mean, if address_of(myglob)-address_of(instruction_that_access_myglob) is a certain value, why do we even have to know the absolute address of myglob?
linux dynamic-linking x86 dynamic-loading
asked Feb 14 at 2:15
炸鱼薯条德里克炸鱼薯条德里克
5311215
I am reading the blog https://eli.thegreenplace.net/2011/11/11/position-independent-code-pic-in-shared-libraries-on-x64
In the part "x64 PIC with data references - an example", it seems that the module is telling the dynamic linker to fill the absolute address of myglob into .got, then the code get that address and read data from that address.
But why does the compiler have to do this, it's a symbol come from itself, why can't just use RIP-relative addressing to access this symbol? Is it because sometimes .data of the module might be load to a unknown offset to .text(instead of always loaded next to .text)?
I mean, if address_of(myglob)-address_of(instruction_that_access_myglob) is a certain value, why do we even have to know the absolute address of myglob?
linux dynamic-linking x86 dynamic-loading
linux dynamic-linking x86 dynamic-loading
asked Feb 14 at 2:15
炸鱼薯条德里克炸鱼薯条德里克
5311215
asked Feb 14 at 2:15
炸鱼薯条德里克炸鱼薯条德里克
5311215
edited Feb 14 at 2:24
炸鱼薯条德里克
asked Feb 14 at 2:15
炸鱼薯条德里克炸鱼薯条德里克
5311215
asked Feb 14 at 2:15
炸鱼薯条德里克炸鱼薯条德里克
5311215
asked Feb 14 at 2:15
炸鱼薯条德里克炸鱼薯条德里克
5311215
5311215
add a comment |
add a comment |
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