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Cc:,,,,,,, Guo Ren <>
Subject: [PATCH V2] riscv: Fixup compile error BUILD_BUG_ON failed
Date: Sun, 28 Jun 2020 16:07:37 +0000
Message-ID: <> (raw)

From: Guo Ren <>

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 <>
Cc: Masami Hiramatsu <>
Cc: Zong Li <>
Changelog V2:
 - Use __always_inline as same as fix_to_virt
 - Use const "const unsigned int" for 2th param

Signed-off-by: Guo Ren <>
 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 d4a64df..3179a4e 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));
 static void patch_unmap(int fixmap)

             reply index

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-28 16:07 guoren [this message]
2020-06-28 16:25 ` Masami Hiramatsu
2020-06-29 23:22   ` Palmer Dabbelt
2020-06-30  0:12     ` Guo Ren

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