linux-kernel - [PATCH v5 2/9] riscv: Fixup compile error BUILD_BUG

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Message-Id: <1608220905-1962-3-git-send-email-guoren@kernel.org>
Date:   Thu, 17 Dec 2020 16:01:38 +0000
From:   guoren@...nel.org
To:     palmerdabbelt@...gle.com, paul.walmsley@...ive.com,
        mhiramat@...nel.org, alankao@...estech.com, rostedt@...dmis.org,
        bjorn.topel@...el.com, pdp7pdp7@...il.com
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        anup@...infault.org, linux-csky@...r.kernel.org,
        greentime.hu@...ive.com, zong.li@...ive.com, guoren@...nel.org,
        me@...ki.ch, Guo Ren <guoren@...ux.alibaba.com>,
        Palmer Dabbelt <palmer@...belt.com>
Subject: [PATCH v5 2/9] riscv: Fixup compile error BUILD_BUG_ON failed

From: Guo Ren <guoren@...ux.alibaba.com>

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@...ux.alibaba.com>
Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org>
Reviewed-by: Pekka Enberg <penberg@...nel.org>
Cc: Paul Walmsley <paul.walmsley@...ive.com>
Cc: Palmer Dabbelt <palmer@...belt.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)
 {
-- 
2.7.4