7 files changed, 167 insertions, 15 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 5cff165b7eb0..4147f76e7988 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -191,6 +191,19 @@ config VECTORS_BASE
         help
           The base address of exception vectors.
 
+config ARM_PATCH_PHYS_VIRT
+        bool "Patch physical to virtual translations at runtime (EXPERIMENTAL)"
+        depends on EXPERIMENTAL
+        depends on !XIP_KERNEL && !THUMB2_KERNEL && MMU
+        depends on !ARCH_MSM
+        depends on !ARCH_REALVIEW || !SPARSEMEM
+        help
+          Patch phys-to-virt translation functions at runtime according to
+          the position of the kernel in system memory.
+
+          This can only be used with non-XIP, non-Thumb2, MMU kernels where
+          the base of physical memory is at a 16MB boundary.
+
 source "init/Kconfig"
 
 source "kernel/Kconfig.freezer"
diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
index 2efec578a62e..7197879e1cb7 100644
--- a/arch/arm/include/asm/memory.h
+++ b/arch/arm/include/asm/memory.h
@@ -24,8 +24,6 @@
  */
 #define UL(x) _AC(x, UL)
 
-#define PHYS_OFFSET     PLAT_PHYS_OFFSET
-
 #ifdef CONFIG_MMU
 
 /*
@@ -135,16 +133,6 @@
 #endif
 
 /*
- * Physical vs virtual RAM address space conversion.  These are
- * private definitions which should NOT be used outside memory.h
- * files.  Use virt_to_phys/phys_to_virt/__pa/__va instead.
- */
-#ifndef __virt_to_phys
-#define __virt_to_phys(x)       ((x) - PAGE_OFFSET + PHYS_OFFSET)
-#define __phys_to_virt(x)       ((x) - PHYS_OFFSET + PAGE_OFFSET)
-#endif
-
-/*
  * Convert a physical address to a Page Frame Number and back
  */
 #define __phys_to_pfn(paddr)    ((paddr) >> PAGE_SHIFT)
@@ -159,6 +147,49 @@
 #ifndef __ASSEMBLY__
 
 /*
+ * Physical vs virtual RAM address space conversion.  These are
+ * private definitions which should NOT be used outside memory.h
+ * files.  Use virt_to_phys/phys_to_virt/__pa/__va instead.
+ */
+#ifndef __virt_to_phys
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
+
+extern unsigned long __pv_phys_offset;
+#define PHYS_OFFSET __pv_phys_offset
+
+#define __pv_stub(from,to,instr)                        \
+        __asm__("@ __pv_stub\n"                         \
+        "1:     " instr "       %0, %1, %2\n"           \
+        "       .pushsection .pv_table,\"a\"\n"         \
+        "       .long   1b\n"                           \
+        "       .popsection\n"                          \
+        : "=r" (to)                                     \
+        : "r" (from), "I" (0x81000000))
+
+static inline unsigned long __virt_to_phys(unsigned long x)
+{
+        unsigned long t;
+        __pv_stub(x, t, "add");
+        return t;
+}
+
+static inline unsigned long __phys_to_virt(unsigned long x)
+{
+        unsigned long t;
+        __pv_stub(x, t, "sub");
+        return t;
+}
+#else
+#define __virt_to_phys(x)       ((x) - PAGE_OFFSET + PHYS_OFFSET)
+#define __phys_to_virt(x)       ((x) - PHYS_OFFSET + PAGE_OFFSET)
+#endif
+#endif
+
+#ifndef PHYS_OFFSET
+#define PHYS_OFFSET     PLAT_PHYS_OFFSET
+#endif
+
+/*
  * The DMA mask corresponding to the maximum bus address allocatable
  * using GFP_DMA.  The default here places no restriction on DMA
  * allocations.  This must be the smallest DMA mask in the system,
diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h
index 12c8e680cbff..d072c21332ee 100644
--- a/arch/arm/include/asm/module.h
+++ b/arch/arm/include/asm/module.h
@@ -25,8 +25,19 @@ struct mod_arch_specific {
 };
 
 /*
- * Include the ARM architecture version.
+ * Add the ARM architecture version to the version magic string
  */
-#define MODULE_ARCH_VERMAGIC    "ARMv" __stringify(__LINUX_ARM_ARCH__) " "
+#define MODULE_ARCH_VERMAGIC_ARMVSN "ARMv" __stringify(__LINUX_ARM_ARCH__) " "
+
+/* Add __virt_to_phys patching state as well */
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
+#define MODULE_ARCH_VERMAGIC_P2V "p2v8 "
+#else
+#define MODULE_ARCH_VERMAGIC_P2V ""
+#endif
+
+#define MODULE_ARCH_VERMAGIC \
+        MODULE_ARCH_VERMAGIC_ARMVSN \
+        MODULE_ARCH_VERMAGIC_P2V
 
 #endif /* _ASM_ARM_MODULE_H */
diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
index e5e1e5387678..9615423c37dd 100644
--- a/arch/arm/kernel/armksyms.c
+++ b/arch/arm/kernel/armksyms.c
@@ -170,3 +170,7 @@ EXPORT_SYMBOL(mcount);
 #endif
 EXPORT_SYMBOL(__gnu_mcount_nc);
 #endif
+
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
+EXPORT_SYMBOL(__pv_phys_offset);
+#endif
diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
index 03a588b6e15c..1db8ead2e331 100644
--- a/arch/arm/kernel/head.S
+++ b/arch/arm/kernel/head.S
@@ -98,6 +98,9 @@ ENTRY(stext)
 #ifdef CONFIG_SMP_ON_UP
         bl      __fixup_smp
 #endif
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
+        bl      __fixup_pv_table
+#endif
         bl      __create_page_tables
 
         /*
@@ -438,4 +441,69 @@ smp_on_up:
 
 #endif
 
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
+
+/* __fixup_pv_table - patch the stub instructions with the delta between
+ * PHYS_OFFSET and PAGE_OFFSET, which is assumed to be 16MiB aligned and
+ * can be expressed by an immediate shifter operand. The stub instruction
+ * has a form of '(add|sub) rd, rn, #imm'.
+ */
+        __HEAD
+__fixup_pv_table:
+        adr     r0, 1f
+        ldmia   r0, {r3-r5, r7}
+        sub     r3, r0, r3      @ PHYS_OFFSET - PAGE_OFFSET
+        add     r4, r4, r3      @ adjust table start address
+        add     r5, r5, r3      @ adjust table end address
+        str     r8, [r7, r3]!   @ save computed PHYS_OFFSET to __pv_phys_offset
+        mov     r6, r3, lsr #24 @ constant for add/sub instructions
+        teq     r3, r6, lsl #24 @ must be 16MiB aligned
+        bne     __error
+        str     r6, [r7, #4]    @ save to __pv_offset
+        b       __fixup_a_pv_table
+ENDPROC(__fixup_pv_table)
+
+        .align
+1:      .long   .
+        .long   __pv_table_begin
+        .long   __pv_table_end
+2:      .long   __pv_phys_offset
+
+        .text
+__fixup_a_pv_table:
+        b       3f
+2:      ldr     ip, [r7, r3]
+        bic     ip, ip, #0x000000ff
+        orr     ip, ip, r6
+        str     ip, [r7, r3]
+3:      cmp     r4, r5
+        ldrcc   r7, [r4], #4    @ use branch for delay slot
+        bcc     2b
+        mov     pc, lr
+ENDPROC(__fixup_a_pv_table)
+
+ENTRY(fixup_pv_table)
+        stmfd   sp!, {r4 - r7, lr}
+        ldr     r2, 2f                  @ get address of __pv_phys_offset
+        mov     r3, #0                  @ no offset
+        mov     r4, r0                  @ r0 = table start
+        add     r5, r0, r1              @ r1 = table size
+        ldr     r6, [r2, #4]            @ get __pv_offset
+        bl      __fixup_a_pv_table
+        ldmfd   sp!, {r4 - r7, pc}
+ENDPROC(fixup_pv_table)
+
+        .align
+2:      .long   __pv_phys_offset
+
+        .data
+        .globl  __pv_phys_offset
+        .type   __pv_phys_offset, %object
+__pv_phys_offset:
+        .long   0
+        .size   __pv_phys_offset, . - __pv_phys_offset
+__pv_offset:
+        .long   0
+#endif
+
 #include "head-common.S"
diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index 2cfe8161b478..c5679f6d9f64 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -268,12 +268,28 @@ struct mod_unwind_map {
         const Elf_Shdr *txt_sec;
 };
 
+static const Elf_Shdr *find_mod_section(const Elf32_Ehdr *hdr,
+        const Elf_Shdr *sechdrs, const char *name)
+{
+        const Elf_Shdr *s, *se;
+        const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
+
+        for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++)
+                if (strcmp(name, secstrs + s->sh_name) == 0)
+                        return s;
+
+        return NULL;
+}
+
+extern void fixup_pv_table(const void *, unsigned long);
+
 int module_finalize(const Elf32_Ehdr *hdr, const Elf_Shdr *sechdrs,
                     struct module *mod)
 {
+        const Elf_Shdr *s = NULL;
 #ifdef CONFIG_ARM_UNWIND
         const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
-        const Elf_Shdr *s, *sechdrs_end = sechdrs + hdr->e_shnum;
+        const Elf_Shdr *sechdrs_end = sechdrs + hdr->e_shnum;
         struct mod_unwind_map maps[ARM_SEC_MAX];
         int i;
 
@@ -315,6 +331,11 @@ int module_finalize(const Elf32_Ehdr *hdr, const Elf_Shdr *sechdrs,
                                                  maps[i].txt_sec->sh_addr,
                                                  maps[i].txt_sec->sh_size);
 #endif
+#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
+        s = find_mod_section(hdr, sechdrs, ".pv_table");
+        if (s)
+                fixup_pv_table((void *)s->sh_addr, s->sh_size);
+#endif
         return 0;
 }
 
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index 86b66f3f2031..45b5651777ee 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -57,6 +57,10 @@ SECTIONS
                 __smpalt_end = .;
 #endif
 
+                __pv_table_begin = .;
+                        *(.pv_table)
+                __pv_table_end = .;
+
                 INIT_SETUP(16)
 
                 INIT_CALLS