arm: fixmap: implement __set_fixmap()

This is used from set_fixmap() and clear_fixmap() via asm-generic/fixmap.h.
Also makes sure that the fixmap allocation fits into the expected range.

Based on patch by Rabin Vincent.

Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Rabin Vincent <rabin@rab.in>
Acked-by: Nicolas Pitre <nico@linaro.org>

diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index d984ca6..714606f 100644 (file)
--- a/arch/arm/include/asm/fixmap.h
+++ b/arch/arm/include/asm/fixmap.h
@@ -14,6 +14,8 @@ enum fixed_addresses {
        __end_of_fixed_addresses
 };
 
+void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot);
+
 #include <asm-generic/fixmap.h>
 
 #endif

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 7fa0966..bdf5c94 100644 (file)
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -22,6 +22,7 @@
 #include <asm/cputype.h>
 #include <asm/sections.h>
 #include <asm/cachetype.h>
+#include <asm/fixmap.h>
 #include <asm/sections.h>
 #include <asm/setup.h>
 #include <asm/smp_plat.h>
@@ -392,6 +393,29 @@ SET_MEMORY_FN(rw, pte_set_rw)
 SET_MEMORY_FN(x, pte_set_x)
 SET_MEMORY_FN(nx, pte_set_nx)
 
+/*
+ * To avoid TLB flush broadcasts, this uses local_flush_tlb_kernel_range().
+ * As a result, this can only be called with preemption disabled, as under
+ * stop_machine().
+ */
+void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
+{
+       unsigned long vaddr = __fix_to_virt(idx);
+       pte_t *pte = pte_offset_kernel(pmd_off_k(vaddr), vaddr);
+
+       /* Make sure fixmap region does not exceed available allocation. */
+       BUILD_BUG_ON(FIXADDR_START + (__end_of_fixed_addresses * PAGE_SIZE) >
+                    FIXADDR_END);
+       BUG_ON(idx >= __end_of_fixed_addresses);
+
+       if (pgprot_val(prot))
+               set_pte_at(NULL, vaddr, pte,
+                       pfn_pte(phys >> PAGE_SHIFT, prot));
+       else
+               pte_clear(NULL, vaddr, pte);
+       local_flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
+}
+
 /*
  * Adjust the PMD section entries according to the CPU in use.
  */