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由 Scott Wood 提交于
ARM64 uses the newer RELA-style relocations rather than the older REL. RELA relocations have an addend in the relocation struct, rather than expecting the loader to read a value from the location to be updated. While this is beneficial for ordinary program loading, it's problematic for U-Boot because the location to be updated starts out with zero, rather than a pre-relocation value. Since we need to be able to run C code before relocation, we need a tool to apply the relocations at build time. In theory this tool is applicable to other newer architectures (mainly 64-bit), but currently the only relocations it supports are for arm64, and it assumes a 64-bit little-endian target. If the latter limitation is ever to be changed, we'll need a way to tell the tool what format the image is in. Eventually this may be replaced by a tool that uses libelf or similar and operates directly on the ELF file. I've written some code for such an approach but libelf does not make it easy to poke addresses by memory address (rather than by section), and I was hesitant to write code to manually parse the program headers and do the update outside of libelf (or to iterate over sections) -- especially since it wouldn't get test coverage on things like binaries with multiple PT_LOAD segments. This should be good enough for now to let the manual relocation stuff be removed from the arm64 patches. Signed-off-by: NScott Wood <scottwood@freescale.com> Signed-off-by: NDavid Feng <fenghua@phytium.com.cn>
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