@@ -413,4 +413,7 @@ alternative_endif
movk \reg, :abs_g0_nc:\val
.endm
+ .macro pte_to_phys, phys, pte
+ and \phys, \pte, #(((1 << (48 - PAGE_SHIFT)) - 1) << PAGE_SHIFT)
+ .endm
#endif /* __ASM_ASSEMBLER_H */
@@ -778,6 +778,30 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
ID_AA64PFR0_CSV3_SHIFT);
}
+static int kpti_install_ng_mappings(void *__unused)
+{
+ typedef void (kpti_remap_fn)(int, int, phys_addr_t);
+ extern kpti_remap_fn idmap_kpti_install_ng_mappings;
+ kpti_remap_fn *remap_fn;
+
+ static bool kpti_applied = false;
+ int cpu = smp_processor_id();
+
+ if (kpti_applied)
+ return 0;
+
+ remap_fn = (void *)__pa_symbol(idmap_kpti_install_ng_mappings);
+
+ cpu_install_idmap();
+ remap_fn(cpu, num_online_cpus(), __pa_symbol(swapper_pg_dir));
+ cpu_uninstall_idmap();
+
+ if (!cpu)
+ kpti_applied = true;
+
+ return 0;
+}
+
static int __init parse_kpti(char *str)
{
bool enabled;
@@ -881,6 +905,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
.capability = ARM64_UNMAP_KERNEL_AT_EL0,
.def_scope = SCOPE_SYSTEM,
.matches = unmap_kernel_at_el0,
+ .enable = kpti_install_ng_mappings,
},
#endif
{},
@@ -148,6 +148,16 @@ alternative_else_nop_endif
ENDPROC(cpu_do_switch_mm)
.pushsection ".idmap.text", "ax"
+
+.macro __idmap_cpu_set_reserved_ttbr1, tmp1, tmp2
+ adrp \tmp1, empty_zero_page
+ msr ttbr1_el1, \tmp1
+ isb
+ tlbi vmalle1
+ dsb nsh
+ isb
+.endm
+
/*
* void idmap_cpu_replace_ttbr1(phys_addr_t new_pgd)
*
@@ -158,13 +168,7 @@ ENTRY(idmap_cpu_replace_ttbr1)
mrs x2, daif
msr daifset, #0xf
- adrp x1, empty_zero_page
- msr ttbr1_el1, x1
- isb
-
- tlbi vmalle1
- dsb nsh
- isb
+ __idmap_cpu_set_reserved_ttbr1 x1, x3
msr ttbr1_el1, x0
isb
@@ -175,6 +179,189 @@ ENTRY(idmap_cpu_replace_ttbr1)
ENDPROC(idmap_cpu_replace_ttbr1)
.popsection
+#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
+ .pushsection ".idmap.text", "ax"
+
+ .macro __idmap_kpti_get_pgtable_ent, type
+ dc cvac, cur_\()\type\()p // Ensure any existing dirty
+ dmb sy // lines are written back before
+ ldr \type, [cur_\()\type\()p] // loading the entry
+ tbz \type, #0, next_\()\type // Skip invalid entries
+ .endm
+
+ .macro __idmap_kpti_put_pgtable_ent_ng, type
+ orr \type, \type, #PTE_NG // Same bit for blocks and pages
+ str \type, [cur_\()\type\()p] // Update the entry and ensure it
+ dc civac, cur_\()\type\()p // is visible to all CPUs.
+ .endm
+
+/*
+ * void __kpti_install_ng_mappings(int cpu, int num_cpus, phys_addr_t swapper)
+ *
+ * Called exactly once from stop_machine context by each CPU found during boot.
+ */
+__idmap_kpti_flag:
+ .long 1
+ENTRY(idmap_kpti_install_ng_mappings)
+ cpu .req w0
+ num_cpus .req w1
+ swapper_pa .req x2
+ swapper_ttb .req x3
+ flag_ptr .req x4
+ cur_pgdp .req x5
+ end_pgdp .req x6
+ pgd .req x7
+ cur_pudp .req x8
+ end_pudp .req x9
+ pud .req x10
+ cur_pmdp .req x11
+ end_pmdp .req x12
+ pmd .req x13
+ cur_ptep .req x14
+ end_ptep .req x15
+ pte .req x16
+
+ mrs swapper_ttb, ttbr1_el1
+ adr flag_ptr, __idmap_kpti_flag
+
+ cbnz cpu, __idmap_kpti_secondary
+
+ /* 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
+
+ /* We need to walk swapper, so turn off the MMU. */
+ mrs x18, sctlr_el1
+ bic x18, x18, #SCTLR_ELx_M
+ msr sctlr_el1, x18
+ isb
+
+ /* Everybody is enjoying the idmap, so we can rewrite swapper. */
+ /* PGD */
+ mov cur_pgdp, swapper_pa
+ add end_pgdp, cur_pgdp, #(PTRS_PER_PGD * 8)
+do_pgd: __idmap_kpti_get_pgtable_ent pgd
+ tbnz pgd, #1, walk_puds
+ __idmap_kpti_put_pgtable_ent_ng pgd
+next_pgd:
+ add cur_pgdp, cur_pgdp, #8
+ cmp cur_pgdp, end_pgdp
+ b.ne do_pgd
+
+ /* Publish the updated tables and nuke all the TLBs */
+ dsb sy
+ tlbi vmalle1is
+ dsb ish
+ isb
+
+ /* We're done: fire up the MMU again */
+ mrs x18, sctlr_el1
+ orr x18, x18, #SCTLR_ELx_M
+ msr sctlr_el1, x18
+ isb
+
+ /* Set the flag to zero to indicate that we're all done */
+ str wzr, [flag_ptr]
+ ret
+
+ /* PUD */
+walk_puds:
+ .if CONFIG_PGTABLE_LEVELS > 3
+ pte_to_phys cur_pudp, pgd
+ add end_pudp, cur_pudp, #(PTRS_PER_PUD * 8)
+do_pud: __idmap_kpti_get_pgtable_ent pud
+ tbnz pud, #1, walk_pmds
+ __idmap_kpti_put_pgtable_ent_ng pud
+next_pud:
+ add cur_pudp, cur_pudp, 8
+ cmp cur_pudp, end_pudp
+ b.ne do_pud
+ b next_pgd
+ .else /* CONFIG_PGTABLE_LEVELS <= 3 */
+ mov pud, pgd
+ b walk_pmds
+next_pud:
+ b next_pgd
+ .endif
+
+ /* PMD */
+walk_pmds:
+ .if CONFIG_PGTABLE_LEVELS > 2
+ pte_to_phys cur_pmdp, pud
+ add end_pmdp, cur_pmdp, #(PTRS_PER_PMD * 8)
+do_pmd: __idmap_kpti_get_pgtable_ent pmd
+ tbnz pmd, #1, walk_ptes
+ __idmap_kpti_put_pgtable_ent_ng pmd
+next_pmd:
+ add cur_pmdp, cur_pmdp, #8
+ cmp cur_pmdp, end_pmdp
+ b.ne do_pmd
+ b next_pud
+ .else /* CONFIG_PGTABLE_LEVELS <= 2 */
+ mov pmd, pud
+ b walk_ptes
+next_pmd:
+ b next_pud
+ .endif
+
+ /* PTE */
+walk_ptes:
+ pte_to_phys cur_ptep, pmd
+ add end_ptep, cur_ptep, #(PTRS_PER_PTE * 8)
+do_pte: __idmap_kpti_get_pgtable_ent pte
+ __idmap_kpti_put_pgtable_ent_ng pte
+next_pte:
+ add cur_ptep, cur_ptep, #8
+ cmp cur_ptep, end_ptep
+ b.ne do_pte
+ b next_pmd
+
+ /* Secondary CPUs end up here */
+__idmap_kpti_secondary:
+ /* Uninstall swapper before surgery begins */
+ __idmap_cpu_set_reserved_ttbr1 x18, 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]
+ cbnz w17, 1b
+
+ /* Wait for the boot CPU to finish messing around with swapper */
+ sevl
+1: wfe
+ ldxr w18, [flag_ptr]
+ cbnz w18, 1b
+
+ /* All done, act like nothing happened */
+ 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
+
/*
* __cpu_setup
*