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Konrad Rzeszutek Wilk 84eabb2754 livepatch: ARM/x86: Check displacement of old_addr and new_addr
If the distance is too big we are in trouble - as our relocation
distance can surely be clipped, or still have a valid width - but
cause an overflow of distance.

On various architectures the maximum displacement for a unconditional
branch/jump varies. ARM32 is +/- 32MB, ARM64 is +/- 128MB while x86
for 32-bit relocations is +/- 2G.

Note: On x86 we could use the 64-bit jmpq instruction which
would provide much bigger displacement to do a jump, but we would
still have issues with the new function not being able to reach
any of the old functions (as all the relocations would assume 32-bit
displacement). And "furthermore would require an register or
memory location to load/store the address to." (From Jan).

On ARM the conditional branch supports even a smaller displacement
but fortunately we are not using that.

Reviewed-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
2016-09-27 22:06:10 -04:00
..
2016-06-17 11:27:21 +01:00
2016-06-17 11:27:21 +01:00
2015-07-08 14:37:43 +01:00
2016-04-01 11:07:28 +08:00

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