arm64: mm: avoid x18 in idmap_kpti_install_ng_mappings

idmap_kpti_install_ng_mappings uses x18 as a temporary register, which
will result in a conflict when x18 is reserved. Use x16 and x17 instead
where needed.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index a1e0592..fdabf40 100644 (file)
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -250,15 +250,15 @@ ENTRY(idmap_kpti_install_ng_mappings)
        /* We're the boot CPU. Wait for the others to catch up */
        sevl
 1:     wfe
-       ldaxr   w18, [flag_ptr]
-       eor     w18, w18, num_cpus
-       cbnz    w18, 1b
+       ldaxr   w17, [flag_ptr]
+       eor     w17, w17, num_cpus
+       cbnz    w17, 1b
 
        /* We need to walk swapper, so turn off the MMU. */
        pre_disable_mmu_workaround
-       mrs     x18, sctlr_el1
-       bic     x18, x18, #SCTLR_ELx_M
-       msr     sctlr_el1, x18
+       mrs     x17, sctlr_el1
+       bic     x17, x17, #SCTLR_ELx_M
+       msr     sctlr_el1, x17
        isb
 
        /* Everybody is enjoying the idmap, so we can rewrite swapper. */
@@ -281,9 +281,9 @@ skip_pgd:
        isb
 
        /* We're done: fire up the MMU again */
-       mrs     x18, sctlr_el1
-       orr     x18, x18, #SCTLR_ELx_M
-       msr     sctlr_el1, x18
+       mrs     x17, sctlr_el1
+       orr     x17, x17, #SCTLR_ELx_M
+       msr     sctlr_el1, x17
        isb
 
        /*
@@ -353,46 +353,47 @@ skip_pte:
        b.ne    do_pte
        b       next_pmd
 
+       .unreq  cpu
+       .unreq  num_cpus
+       .unreq  swapper_pa
+       .unreq  cur_pgdp
+       .unreq  end_pgdp
+       .unreq  pgd
+       .unreq  cur_pudp
+       .unreq  end_pudp
+       .unreq  pud
+       .unreq  cur_pmdp
+       .unreq  end_pmdp
+       .unreq  pmd
+       .unreq  cur_ptep
+       .unreq  end_ptep
+       .unreq  pte
+
        /* Secondary CPUs end up here */
 __idmap_kpti_secondary:
        /* Uninstall swapper before surgery begins */
-       __idmap_cpu_set_reserved_ttbr1 x18, x17
+       __idmap_cpu_set_reserved_ttbr1 x16, x17
 
        /* Increment the flag to let the boot CPU we're ready */
-1:     ldxr    w18, [flag_ptr]
-       add     w18, w18, #1
-       stxr    w17, w18, [flag_ptr]
+1:     ldxr    w16, [flag_ptr]
+       add     w16, w16, #1
+       stxr    w17, w16, [flag_ptr]
        cbnz    w17, 1b
 
        /* Wait for the boot CPU to finish messing around with swapper */
        sevl
 1:     wfe
-       ldxr    w18, [flag_ptr]
-       cbnz    w18, 1b
+       ldxr    w16, [flag_ptr]
+       cbnz    w16, 1b
 
        /* All done, act like nothing happened */
-       offset_ttbr1 swapper_ttb, x18
+       offset_ttbr1 swapper_ttb, x16
        msr     ttbr1_el1, swapper_ttb
        isb
        ret
 
-       .unreq  cpu
-       .unreq  num_cpus
-       .unreq  swapper_pa
        .unreq  swapper_ttb
        .unreq  flag_ptr
-       .unreq  cur_pgdp
-       .unreq  end_pgdp
-       .unreq  pgd
-       .unreq  cur_pudp
-       .unreq  end_pudp
-       .unreq  pud
-       .unreq  cur_pmdp
-       .unreq  end_pmdp
-       .unreq  pmd
-       .unreq  cur_ptep
-       .unreq  end_ptep
-       .unreq  pte
 ENDPROC(idmap_kpti_install_ng_mappings)
        .popsection
 #endif