[PATCH v2 3/3] RISC-V: add compiler barriers around unrelocated accesses

[Ahmad Fatoum]

We observed on ARM miscompilation because get_runtime_offset() was
cached before relocation, while address computation of symbol happened
after, effectively adding the base address twice to the symbol offset.

New runtime_address() hides origin of the symbol going into the address
calculation and thereby thwarts this optimization. Employ it in RISC-V
code as well to avoid such issues as experienced on ARM.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
 arch/riscv/boot/uncompress.c      |  4 ++--
 arch/riscv/include/asm/sections.h |  3 ++-
 arch/riscv/lib/reloc.c            | 10 +++++++---
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/boot/uncompress.c b/arch/riscv/boot/uncompress.c
index 4ed9b4d37192..4addd49e7389 100644
--- a/arch/riscv/boot/uncompress.c
+++ b/arch/riscv/boot/uncompress.c
@@ -36,8 +36,8 @@ void __noreturn barebox_pbl_start(unsigned long membase, unsigned long memsize,
 	irq_init_vector(__riscv_mode(flags));
 
 	/* piggy data is not relocated, so determine the bounds now */
-	pg_start = input_data + get_runtime_offset();
-	pg_end = input_data_end + get_runtime_offset();
+	pg_start = runtime_address(input_data);
+	pg_end = runtime_address(input_data_end);
 	pg_len = pg_end - pg_start;
 	uncompressed_len = input_data_len();
 
diff --git a/arch/riscv/include/asm/sections.h b/arch/riscv/include/asm/sections.h
index 6673648bcd58..cea039cc5e14 100644
--- a/arch/riscv/include/asm/sections.h
+++ b/arch/riscv/include/asm/sections.h
@@ -6,6 +6,7 @@
 #include <asm-generic/sections.h>
 #include <linux/types.h>
 #include <asm/unaligned.h>
+#include <asm/reloc.h>
 
 extern char __rel_dyn_start[];
 extern char __rel_dyn_end[];
@@ -19,7 +20,7 @@ unsigned long get_runtime_offset(void);
 
 static inline unsigned int input_data_len(void)
 {
-	return get_unaligned((const u32 *)(input_data_end + get_runtime_offset() - 4));
+	return get_unaligned((const u32 *)runtime_address(input_data_end) - 1);
 }
 
 #endif
diff --git a/arch/riscv/lib/reloc.c b/arch/riscv/lib/reloc.c
index da53c50448d7..86a4b3719d5f 100644
--- a/arch/riscv/lib/reloc.c
+++ b/arch/riscv/lib/reloc.c
@@ -42,9 +42,13 @@ void relocate_to_current_adr(void)
 	if (!offset)
 		return;
 
-	dstart = __rel_dyn_start + offset;
-	dend = __rel_dyn_end + offset;
-	dynsym = (void *)__dynsym_start + offset;
+	/*
+	 * We have yet to relocate, so using runtime_address
+	 * to compute the relocated address
+	 */
+	dstart = runtime_address(__rel_dyn_start);
+	dend = runtime_address(__rel_dyn_end);
+	dynsym = runtime_address(__dynsym_start);
 
 	for (rela = dstart; (void *)rela < dend; rela++) {
 		unsigned long *fixup;
-- 
2.30.2