Position independent code with fixed data and bss

Christopher Collins · 2015-07-07T00:44:11+00:00

MCU: STM32F4 (ARM Cortex M4) Build environment: arm-none-eabi-gcc 4.8.4 20140725 My goal is to build an image that can be run from any properly-aligned offset in internal flash (i.e., position-independent). I found the following set of gcc flags that achieves this goal: # Generate position independent code. -fPIC # Access bss via the GOT. -mno-pic-data-is-text-relative # GOT is not PC-relative; store GOT location in a register. -msingle-pic-base # Store GOT location in r9. -mpic-register=r9 This works, but now I am wondering if there is a way to reduce the size of the resulting binary. In particular, the above flags cause all global variables to be accessed via the global offset table (GOT). However, I don't need this extra indirection, because the data and bss sections will always be at fixed offsets in SRAM. The only part of the image that needs to be position independent is the code itself. Ideally, I would like to gcc to treat all accesses to global variables as though it weren't generating position-independent code. Any ideas? All input is greatly appreciated. Chris

Jul 07, 2015 20 Replies

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omarisaip 8 years ago

Hi Christ,

Did you find a solution for this?

Omar

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Position independent code with fixed data and bss

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