riscv: KGDB: Do not inline arch_kgdb_breakpoint()

[ Upstream commit 3af4bec ]

The arch_kgdb_breakpoint() function defines the kgdb_compiled_break
symbol using inline assembly.

There's a potential issue where the compiler might inline
arch_kgdb_breakpoint(), which would then define the kgdb_compiled_break
symbol multiple times, leading to fail to link vmlinux.o.

This isn't merely a potential compilation problem. The intent here
is to determine the global symbol address of kgdb_compiled_break,
and if this function is inlined multiple times, it would logically
be a grave error.

Link: https://lore.kernel.org/all/[email protected]/
Link: https://lore.kernel.org/all/[email protected]/
Link: https://lore.kernel.org/all/[email protected]/
Fixes: fe89bd2 ("riscv: Add KGDB support")
Co-developed-by: Huacai Chen <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>
Signed-off-by: WangYuli <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Palmer Dabbelt <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

Author: Avenger-285714

arch/riscv/include/asm/kgdb.h

@@ -19,16 +19,9 @@
 
 #ifndef	__ASSEMBLY__
 
+void arch_kgdb_breakpoint(void);
 extern unsigned long kgdb_compiled_break;
 
-static inline void arch_kgdb_breakpoint(void)
-{
-	asm(".global kgdb_compiled_break\n"
-	    ".option norvc\n"
-	    "kgdb_compiled_break: ebreak\n"
-	    ".option rvc\n");
-}
-
 #endif /* !__ASSEMBLY__ */
 
 #define DBG_REG_ZERO "zero"

arch/riscv/kernel/kgdb.c

@@ -254,6 +254,14 @@ void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
 	regs->epc = pc;
 }
 
+noinline void arch_kgdb_breakpoint(void)
+{
+	asm(".global kgdb_compiled_break\n"
+	    ".option norvc\n"
+	    "kgdb_compiled_break: ebreak\n"
+	    ".option rvc\n");
+}
+
 void kgdb_arch_handle_qxfer_pkt(char *remcom_in_buffer,
 				char *remcom_out_buffer)
 {