[PATCH v5 2/9] riscv: Fixup compile error BUILD_BUG_ON failed

guoren
2020-12-17T16:03:47Z

Unfortunately, the current code couldn't be compiled:

CC arch/riscv/kernel/patch.o
In file included from ./include/linux/kernel.h:11,
from ./include/linux/list.h:9,
from ./include/linux/preempt.h:11,
from ./include/linux/spinlock.h:51,
from arch/riscv/kernel/patch.c:6:
In function ‘fix_to_virt’,
inlined from ‘patch_map’ at arch/riscv/kernel/patch.c:37:17:
./include/linux/compiler.h:392:38: error: call to ‘__compiletime_assert_205’ declared with attribute error: BUILD_BUG_ON failed: idx >= __end_of_fixed_addresses
_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
^
./include/linux/compiler.h:373:4: note: in definition of macro ‘__compiletime_assert’
prefix ## suffix(); \
^~~~~~
./include/linux/compiler.h:392:2: note: in expansion of macro ‘_compiletime_assert’
_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
^~~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:39:37: note: in expansion of macro ‘compiletime_assert’
#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
^~~~~~~~~~~~~~~~~~
./include/linux/build_bug.h:50:2: note: in expansion of macro ‘BUILD_BUG_ON_MSG’
BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
^~~~~~~~~~~~~~~~
./include/asm-generic/fixmap.h:32:2: note: in expansion of macro ‘BUILD_BUG_ON’
BUILD_BUG_ON(idx >= __end_of_fixed_addresses);
^~~~~~~~~~~~

Because fix_to_virt(, idx) needs a const value, not a dynamic variable of
reg-a0 or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
---
arch/riscv/kernel/patch.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
index 3fe7a52..0b55287 100644
--- a/arch/riscv/kernel/patch.c
+++ b/arch/riscv/kernel/patch.c
@@ -20,7 +20,12 @@ struct patch_insn {
};

#ifdef CONFIG_MMU
-static void *patch_map(void *addr, int fixmap)
+/*
+ * The fix_to_virt(, idx) needs a const value (not a dynamic variable of
+ * reg-a0) or BUILD_BUG_ON failed with "idx >= __end_of_fixed_addresses".
+ * So use '__always_inline' and 'const unsigned int fixmap' here.
+ */
+static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
{
uintptr_t uintaddr = (uintptr_t) addr;
struct page *page;
@@ -37,7 +42,6 @@ static void *patch_map(void *addr, int fixmap)
return (void *)set_fixmap_offset(fixmap, page_to_phys(page) +
(uintaddr & ~PAGE_MASK));
}
-NOKPROBE_SYMBOL(patch_map);

static void patch_unmap(int fixmap)
{