arm64: assembler: make adr_l work in modules under KASLR

commit 41c066f2c4d436c535616fe182331766c57838f0 upstream

When CONFIG_RANDOMIZE_MODULE_REGION_FULL=y, the offset between loaded
modules and the core kernel may exceed 4 GB, putting symbols exported
by the core kernel out of the reach of the ordinary adrp/add instruction
pairs used to generate relative symbol references. So make the adr_l
macro emit a movz/movk sequence instead when executing in module context.

While at it, remove the pointless special case for the stack pointer.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ dannf: backported to v4.4 by replacing the 3-arg adr_l macro in head.S
  with it's output, as this commit drops the 3-arg variant ]
Fixes: c042dd600f4e ("crypto: arm64/sha - avoid non-standard inline asm tricks")
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index f68abb17aa4b2c35735fe958b969ad0c773c54bb..7c287917bbbdc4835fe166f68a9cade2b494b532 100644 (file)
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -148,22 +148,25 @@ lr        .req    x30             // link register
 
 /*
  * Pseudo-ops for PC-relative adr/ldr/str <reg>, <symbol> where
- * <symbol> is within the range +/- 4 GB of the PC.
+ * <symbol> is within the range +/- 4 GB of the PC when running
+ * in core kernel context. In module context, a movz/movk sequence
+ * is used, since modules may be loaded far away from the kernel
+ * when KASLR is in effect.
  */
        /*
         * @dst: destination register (64 bit wide)
         * @sym: name of the symbol
-        * @tmp: optional scratch register to be used if <dst> == sp, which
-        *       is not allowed in an adrp instruction
         */
-       .macro  adr_l, dst, sym, tmp=
-       .ifb    \tmp
+       .macro  adr_l, dst, sym
+#ifndef MODULE
        adrp    \dst, \sym
        add     \dst, \dst, :lo12:\sym
-       .else
-       adrp    \tmp, \sym
-       add     \dst, \tmp, :lo12:\sym
-       .endif
+#else
+       movz    \dst, #:abs_g3:\sym
+       movk    \dst, #:abs_g2_nc:\sym
+       movk    \dst, #:abs_g1_nc:\sym
+       movk    \dst, #:abs_g0_nc:\sym
+#endif
        .endm
 
        /*
@@ -174,6 +177,7 @@ lr  .req    x30             // link register
         *       the address
         */
        .macro  ldr_l, dst, sym, tmp=
+#ifndef MODULE
        .ifb    \tmp
        adrp    \dst, \sym
        ldr     \dst, [\dst, :lo12:\sym]
@@ -181,6 +185,15 @@ lr .req    x30             // link register
        adrp    \tmp, \sym
        ldr     \dst, [\tmp, :lo12:\sym]
        .endif
+#else
+       .ifb    \tmp
+       adr_l   \dst, \sym
+       ldr     \dst, [\dst]
+       .else
+       adr_l   \tmp, \sym
+       ldr     \dst, [\tmp]
+       .endif
+#endif
        .endm
 
        /*
@@ -190,8 +203,13 @@ lr .req    x30             // link register
         *       while <src> needs to be preserved.
         */
        .macro  str_l, src, sym, tmp
+#ifndef MODULE
        adrp    \tmp, \sym
        str     \src, [\tmp, :lo12:\sym]
+#else
+       adr_l   \tmp, \sym
+       str     \src, [\tmp]
+#endif
        .endm
 
 /*

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 6299a8a361eeeb19f341ccaf5b39a0aeb64c3c7a..504bcc3a852f9488f1a73afb1dcea54ae197e4e5 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -424,7 +424,8 @@ __mmap_switched:
        str     xzr, [x6], #8                   // Clear BSS
        b       1b
 2:
-       adr_l   sp, initial_sp, x4
+       adrp    x4, initial_sp
+       add     sp, x4, :lo12:initial_sp
        str_l   x21, __fdt_pointer, x5          // Save FDT pointer
        str_l   x24, memstart_addr, x6          // Save PHYS_OFFSET
        mov     x29, #0