[PATCH v3 01/17] arm64: mm: avoid x18 in idmap_kpti_install_ng_mappings

samitolvanen
2019-10-31T16:59:06Z

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>
---
arch/arm64/mm/proc.S | 63 ++++++++++++++++++++++----------------------
1 file changed, 32 insertions(+), 31 deletions(-)

diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index a1e0592d1fbc..fdabf40a83c8 100644
--- 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
--
2.24.0.rc0.303.g954a862665-goog