arm64: vmlinux.ld.S: add assertion for reserved_pg_dir offset

Add RESERVED_SWAPPER_OFFSET and use that instead of hardcoding
the offset between swapper_pg_dir and reserved_pg_dir.

Then use RESERVED_SWAPPER_OFFSET to assert that the offset is
correct at link time.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210202123658.22308-2-joey.gouly@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
index 9990059..ccedf54 100644 (file)
--- a/arch/arm64/include/asm/asm-uaccess.h
+++ b/arch/arm64/include/asm/asm-uaccess.h
@@ -15,10 +15,10 @@
        .macro  __uaccess_ttbr0_disable, tmp1
        mrs     \tmp1, ttbr1_el1                        // swapper_pg_dir
        bic     \tmp1, \tmp1, #TTBR_ASID_MASK
-       sub     \tmp1, \tmp1, #PAGE_SIZE                // reserved_pg_dir just before swapper_pg_dir
+       sub     \tmp1, \tmp1, #RESERVED_SWAPPER_OFFSET  // reserved_pg_dir
        msr     ttbr0_el1, \tmp1                        // set reserved TTBR0_EL1
        isb
-       add     \tmp1, \tmp1, #PAGE_SIZE
+       add     \tmp1, \tmp1, #RESERVED_SWAPPER_OFFSET
        msr     ttbr1_el1, \tmp1                // set reserved ASID
        isb
        .endm

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index 18fce22..f6bf8a9 100644 (file)
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -159,6 +159,12 @@
 #define IOREMAP_MAX_ORDER      (PMD_SHIFT)
 #endif
 
+/*
+ *  Open-coded (swapper_pg_dir - reserved_pg_dir) as this cannot be calculated
+ *  until link time.
+ */
+#define RESERVED_SWAPPER_OFFSET        (PAGE_SIZE)
+
 #ifndef __ASSEMBLY__
 
 #include <linux/bitops.h>

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index f0fe0cc..0deb884 100644 (file)
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -87,7 +87,7 @@ static inline void __uaccess_ttbr0_disable(void)
        ttbr = read_sysreg(ttbr1_el1);
        ttbr &= ~TTBR_ASID_MASK;
        /* reserved_pg_dir placed before swapper_pg_dir */
-       write_sysreg(ttbr - PAGE_SIZE, ttbr0_el1);
+       write_sysreg(ttbr - RESERVED_SWAPPER_OFFSET, ttbr0_el1);
        isb();
        /* Set reserved ASID */
        write_sysreg(ttbr, ttbr1_el1);

diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 4c0b0c8..a03a530 100644 (file)
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -316,3 +316,6 @@ ASSERT((__entry_tramp_text_end - __entry_tramp_text_start) == PAGE_SIZE,
  * If padding is applied before .head.text, virt<->phys conversions will fail.
  */
 ASSERT(_text == KIMAGE_VADDR, "HEAD is misaligned")
+
+ASSERT(swapper_pg_dir - reserved_pg_dir == RESERVED_SWAPPER_OFFSET,
+       "RESERVED_SWAPPER_OFFSET is wrong!")