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powerpc/fsl: Add infrastructure to fixup branch predictor flush

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In order to protect against speculation attacks (Spectre
variant 2) on NXP PowerPC platforms, the branch predictor
should be flushed when the privillege level is changed.
This patch is adding the infrastructure to fixup at runtime
the code sections that are performing the branch predictor flush
depending on a boot arg parameter which is added later in a
separate patch.

Signed-off-by: Diana Craciun <diana.craciun@nxp.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Diana Craciun
2018-12-12 16:03:00 +02:00
committed by Michael Ellerman
parent f242e0ac95
commit 76a5eaa38b
4 changed files with 45 additions and 0 deletions
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23
arch/powerpc/lib/feature-fixups.c
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@@ -347,6 +347,29 @@ void do_barrier_nospec_fixups_range(bool enable, void *fixup_start, void *fixup_
printk(KERN_DEBUG "barrier-nospec: patched %d locations\n", i);
}
static void patch_btb_flush_section(long *curr)
{
unsigned int *start, *end;
start = (void *)curr + *curr;
end = (void *)curr + *(curr + 1);
for (; start < end; start++) {
pr_devel("patching dest %lx\n", (unsigned long)start);
patch_instruction(start, PPC_INST_NOP);
}
}
void do_btb_flush_fixups(void)
{
long *start, *end;
start = PTRRELOC(&__start__btb_flush_fixup);
end = PTRRELOC(&__stop__btb_flush_fixup);
for (; start < end; start += 2)
patch_btb_flush_section(start);
}
#endif /* CONFIG_PPC_FSL_BOOK3E */
void do_lwsync_fixups(unsigned long value, void *fixup_start, void *fixup_end)