linux-kernel - [PATCH v6 3/8] arm: fixmap: implement __set

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Message-Id: <1411067949-10913-4-git-send-email-keescook@chromium.org>
Date:	Thu, 18 Sep 2014 12:19:04 -0700
From:	Kees Cook <keescook@...omium.org>
To:	linux-kernel@...r.kernel.org
Cc:	Kees Cook <keescook@...omium.org>, Rabin Vincent <rabin@....in>,
	Will Deacon <will.deacon@....com>,
	Laura Abbott <lauraa@...eaurora.org>,
	Rob Herring <robh@...nel.org>,
	Leif Lindholm <leif.lindholm@...aro.org>,
	Mark Salter <msalter@...hat.com>, Liu hua <sdu.liu@...wei.com>,
	Nikolay Borisov <Nikolay.Borisov@....com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Doug Anderson <dianders@...gle.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v6 3/8] 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@...omium.org>
Cc: Rabin Vincent <rabin@....in>
Acked-by: Nicolas Pitre <nico@...aro.org>
---
 arch/arm/include/asm/fixmap.h |  2 ++
 arch/arm/mm/mmu.c             | 24 ++++++++++++++++++++++++
 2 files changed, 26 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..bdf5c94f7c36 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>
@@ -393,6 +394,29 @@ 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.
  */
 static void __init build_mem_type_table(void)
-- 
1.9.1

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