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| H A D | bl31_entrypoint.S | c3260f9b82c5017ca078f090c03cd7135ee8f8c9 Wed Apr 30 14:36:37 UTC 2014 Soby Mathew <soby.mathew@arm.com> Preserve x19-x29 across world switch for exception handling
Previously exception handlers in BL3-1, X19-X29 were not saved
and restored on every SMC/trap into EL3. Instead these registers
were 'saved as needed' as a side effect of the A64 ABI used by the C
compiler.
That approach failed when world switching but was not visible
with the TSP/TSPD code because the TSP is 64-bit, did not
clobber these registers when running and did not support pre-emption
by normal world interrupts. These scenarios showed
that the values in these registers can be passed through a world
switch, which broke the normal and trusted world assumptions
about these registers being preserved.
The Ideal solution saves and restores these registers when a
world switch occurs - but that type of implementation is more complex.
So this patch always saves and restores these registers on entry and
exit of EL3.
Fixes ARM-software/tf-issues#141
Change-Id: I9a727167bbc594454e81cf78a97ca899dfb11c27
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| H A D | runtime_exceptions.S | c3260f9b82c5017ca078f090c03cd7135ee8f8c9 Wed Apr 30 14:36:37 UTC 2014 Soby Mathew <soby.mathew@arm.com> Preserve x19-x29 across world switch for exception handling
Previously exception handlers in BL3-1, X19-X29 were not saved
and restored on every SMC/trap into EL3. Instead these registers
were 'saved as needed' as a side effect of the A64 ABI used by the C
compiler.
That approach failed when world switching but was not visible
with the TSP/TSPD code because the TSP is 64-bit, did not
clobber these registers when running and did not support pre-emption
by normal world interrupts. These scenarios showed
that the values in these registers can be passed through a world
switch, which broke the normal and trusted world assumptions
about these registers being preserved.
The Ideal solution saves and restores these registers when a
world switch occurs - but that type of implementation is more complex.
So this patch always saves and restores these registers on entry and
exit of EL3.
Fixes ARM-software/tf-issues#141
Change-Id: I9a727167bbc594454e81cf78a97ca899dfb11c27
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