[PATCH v5 3/8] arm: fixmap: implement __set_fixmap()

Kees Cook
2014-09-03T22:00:05Z

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>
---
arch/arm/include/asm/fixmap.h | 2 ++
arch/arm/mm/mmu.c | 25 +++++++++++++++++++++++++
2 files changed, 27 insertions(+)

diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
index d984ca69ce19..714606f70425 100644
--- 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 7fa0966cd15f..fa3a667852cb 100644
--- 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 +393,30 @@ SET_MEMORY_FN(rw, pte_set_rw)
SET_MEMORY_FN(x, pte_set_x)
SET_MEMORY_FN(nx, pte_set_nx)

+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);
+
+ /*
+ * Given the potential a15 tlbi errata, we can only do tlb flushes
+ * with interrupts disabled. Callers must have taken care of this.
+ */
+ WARN_ON_ONCE(!irqs_disabled());
+ flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE);
+}
+
/*
* Adjust the PMD section entries according to the CPU in use.
*/
--
1.9.1