arch/arm64/kernel/ftrace.c:147:15: warning: no previous prototype for function 'arch_ftrace_get_symaddr'

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git topic/fprobe-on-fgraph
head:   e6369db4372d722c47a45887eeb6a0f483c20ced
commit: e01d449c6f4e427bd6a67f3c1eee29f46ac59770 [18/19] ftrace: Add ftrace_get_symaddr to convert fentry_ip to symaddr
config: arm64-randconfig-001-20241206 (https://download.01.org/0day-ci/archive/20241206/[email protected]/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241206/[email protected]/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All warnings (new ones prefixed by >>):

>> arch/arm64/kernel/ftrace.c:147:15: warning: no previous prototype for function 'arch_ftrace_get_symaddr' [-Wmissing-prototypes]
   unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
                 ^

arch/arm64/kernel/ftrace.c:147:1: note: declare 'static' if the function is not intended to be used outside of this translation unit unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
^
static
1 warning generated.

vim +/arch_ftrace_get_symaddr +147 arch/arm64/kernel/ftrace.c

145
146 /* Convert fentry_ip to the symbol address without kallsyms */

 > 147	unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)

148 {
149 u32 insn;
150
151 /*
152 * When using patchable-function-entry without pre-function NOPS, ftrace
153 * entry is the address of the first NOP after the function entry point.
154 *
155 * The compiler has either generated:
156 *
157 * func+00: func: NOP // To be patched to MOV X9, LR
158 * func+04: NOP // To be patched to BL <caller>
159 *
160 * Or:
161 *
162 * func-04: BTI C
163 * func+00: func: NOP // To be patched to MOV X9, LR
164 * func+04: NOP // To be patched to BL <caller>
165 *
166 * The fentry_ip is the address of BL <caller> which is at func + 4
167 * bytes in either case.
168 */
169 if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))
170 return fentry_ip - AARCH64_INSN_SIZE;
171
172 /*
173 * When using patchable-function-entry with pre-function NOPs, BTI is
174 * a bit different.
175 *
176 * func+00: func: NOP // To be patched to MOV X9, LR
177 * func+04: NOP // To be patched to BL <caller>
178 *
179 * Or:
180 *
181 * func+00: func: BTI C
182 * func+04: NOP // To be patched to MOV X9, LR
183 * func+08: NOP // To be patched to BL <caller>
184 *
185 * The fentry_ip is the address of BL <caller> which is at either
186 * func + 4 or func + 8 depends on whether there is a BTI.
187 */
188
189 /* If there is no BTI, the func address should be one instruction before. */
190 if (!IS_ENABLED(CONFIG_ARM64_BTI_KERNEL))
191 return fentry_ip - AARCH64_INSN_SIZE;
192
193 /* We want to be extra safe in case entry ip is on the page edge,
194 * but otherwise we need to avoid get_kernel_nofault()'s overhead.
195 */
196 if ((fentry_ip & ~PAGE_MASK) < AARCH64_INSN_SIZE * 2) {
197 if (get_kernel_nofault(insn, (u32 *)(fentry_ip - AARCH64_INSN_SIZE * 2)))
198 return 0;
199 } else {
200 insn = *(u32 *)(fentry_ip - AARCH64_INSN_SIZE * 2);
201 }
202
203 if (aarch64_insn_is_bti(le32_to_cpu((__le32)insn)))
204 return fentry_ip - AARCH64_INSN_SIZE * 2;
205
206 return fentry_ip - AARCH64_INSN_SIZE;
207 }
208

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