[PATCH 1/2] powerpc64/bpf: Implement JIT support for private stack
kernel test robot
lkp at intel.com
Tue Feb 17 06:14:34 AEDT 2026
Hi,
kernel test robot noticed the following build warnings:
[auto build test WARNING on bpf-next/master]
[also build test WARNING on bpf/master powerpc/next linus/master next-20260216]
[cannot apply to bpf-next/net powerpc/fixes v6.19]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/adubey-linux-ibm-com/selftests-bpf-Enable-private-stack-tests-for-powerpc64/20260216-182353
base: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master
patch link: https://lore.kernel.org/r/20260216152234.36632-1-adubey%40linux.ibm.com
patch subject: [PATCH 1/2] powerpc64/bpf: Implement JIT support for private stack
config: powerpc-randconfig-001-20260217 (https://download.01.org/0day-ci/archive/20260217/202602170316.V2RZWuVa-lkp@intel.com/config)
compiler: powerpc-linux-gcc (GCC) 8.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260217/202602170316.V2RZWuVa-lkp@intel.com/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 <lkp at intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602170316.V2RZWuVa-lkp@intel.com/
All warnings (new ones prefixed by >>):
arch/powerpc/net/bpf_jit_comp.c: In function 'bpf_int_jit_compile':
>> arch/powerpc/net/bpf_jit_comp.c:266:35: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
cgctx.priv_sp = priv_stack_ptr ? (u64)priv_stack_ptr : 0;
^
vim +266 arch/powerpc/net/bpf_jit_comp.c
164
165 struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
166 {
167 u32 proglen;
168 u32 alloclen;
169 u8 *image = NULL;
170 u32 *code_base;
171 u32 *addrs;
172 struct powerpc_jit_data *jit_data;
173 struct codegen_context cgctx;
174 int pass;
175 int flen;
176 int priv_stack_alloc_size;
177 void __percpu *priv_stack_ptr = NULL;
178 struct bpf_binary_header *fhdr = NULL;
179 struct bpf_binary_header *hdr = NULL;
180 struct bpf_prog *org_fp = fp;
181 struct bpf_prog *tmp_fp;
182 bool bpf_blinded = false;
183 bool extra_pass = false;
184 u8 *fimage = NULL;
185 u32 *fcode_base;
186 u32 extable_len;
187 u32 fixup_len;
188
189 if (!fp->jit_requested)
190 return org_fp;
191
192 tmp_fp = bpf_jit_blind_constants(org_fp);
193 if (IS_ERR(tmp_fp))
194 return org_fp;
195
196 if (tmp_fp != org_fp) {
197 bpf_blinded = true;
198 fp = tmp_fp;
199 }
200
201 jit_data = fp->aux->jit_data;
202 if (!jit_data) {
203 jit_data = kzalloc(sizeof(*jit_data), GFP_KERNEL);
204 if (!jit_data) {
205 fp = org_fp;
206 goto out;
207 }
208 fp->aux->jit_data = jit_data;
209 }
210
211 if (!priv_stack_ptr && fp->aux->jits_use_priv_stack) {
212 /*
213 * Allocate private stack of size equivalent to
214 * verifier-calculated stack size plus two memory
215 * guard regions to detect private stack overflow
216 * and underflow.
217 */
218 priv_stack_alloc_size = round_up(fp->aux->stack_depth, 16) +
219 2 * PRIV_STACK_GUARD_SZ;
220 priv_stack_ptr = __alloc_percpu_gfp(priv_stack_alloc_size, 16, GFP_KERNEL);
221 if (!priv_stack_ptr) {
222 fp = org_fp;
223 goto out_priv_stack;
224 }
225
226 priv_stack_init_guard(priv_stack_ptr, priv_stack_alloc_size);
227 fp->aux->priv_stack_ptr = priv_stack_ptr;
228 }
229
230 flen = fp->len;
231 addrs = jit_data->addrs;
232 if (addrs) {
233 cgctx = jit_data->ctx;
234 /*
235 * JIT compiled to a writable location (image/code_base) first.
236 * It is then moved to the readonly final location (fimage/fcode_base)
237 * using instruction patching.
238 */
239 fimage = jit_data->fimage;
240 fhdr = jit_data->fhdr;
241 proglen = jit_data->proglen;
242 hdr = jit_data->hdr;
243 image = (void *)hdr + ((void *)fimage - (void *)fhdr);
244 extra_pass = true;
245 /* During extra pass, ensure index is reset before repopulating extable entries */
246 cgctx.exentry_idx = 0;
247 goto skip_init_ctx;
248 }
249
250 addrs = kcalloc(flen + 1, sizeof(*addrs), GFP_KERNEL);
251 if (addrs == NULL) {
252 fp = org_fp;
253 goto out_addrs;
254 }
255
256 memset(&cgctx, 0, sizeof(struct codegen_context));
257 bpf_jit_init_reg_mapping(&cgctx);
258
259 /* Make sure that the stack is quadword aligned. */
260 cgctx.stack_size = round_up(fp->aux->stack_depth, 16);
261 cgctx.arena_vm_start = bpf_arena_get_kern_vm_start(fp->aux->arena);
262 cgctx.user_vm_start = bpf_arena_get_user_vm_start(fp->aux->arena);
263 cgctx.is_subprog = bpf_is_subprog(fp);
264 cgctx.exception_boundary = fp->aux->exception_boundary;
265 cgctx.exception_cb = fp->aux->exception_cb;
> 266 cgctx.priv_sp = priv_stack_ptr ? (u64)priv_stack_ptr : 0;
267
268 /* Scouting faux-generate pass 0 */
269 if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) {
270 /* We hit something illegal or unsupported. */
271 fp = org_fp;
272 goto out_addrs;
273 }
274
275 /*
276 * If we have seen a tail call, we need a second pass.
277 * This is because bpf_jit_emit_common_epilogue() is called
278 * from bpf_jit_emit_tail_call() with a not yet stable ctx->seen.
279 * We also need a second pass if we ended up with too large
280 * a program so as to ensure BPF_EXIT branches are in range.
281 */
282 if (cgctx.seen & SEEN_TAILCALL || !is_offset_in_branch_range((long)cgctx.idx * 4)) {
283 cgctx.idx = 0;
284 if (bpf_jit_build_body(fp, NULL, NULL, &cgctx, addrs, 0, false)) {
285 fp = org_fp;
286 goto out_addrs;
287 }
288 }
289
290 bpf_jit_realloc_regs(&cgctx);
291 /*
292 * Pretend to build prologue, given the features we've seen. This will
293 * update ctgtx.idx as it pretends to output instructions, then we can
294 * calculate total size from idx.
295 */
296 bpf_jit_build_prologue(NULL, &cgctx);
297 addrs[fp->len] = cgctx.idx * 4;
298 bpf_jit_build_epilogue(NULL, &cgctx);
299
300 fixup_len = fp->aux->num_exentries * BPF_FIXUP_LEN * 4;
301 extable_len = fp->aux->num_exentries * sizeof(struct exception_table_entry);
302
303 proglen = cgctx.idx * 4;
304 alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len;
305
306 fhdr = bpf_jit_binary_pack_alloc(alloclen, &fimage, 4, &hdr, &image,
307 bpf_jit_fill_ill_insns);
308 if (!fhdr) {
309 fp = org_fp;
310 goto out_addrs;
311 }
312
313 if (extable_len)
314 fp->aux->extable = (void *)fimage + FUNCTION_DESCR_SIZE + proglen + fixup_len;
315
316 skip_init_ctx:
317 code_base = (u32 *)(image + FUNCTION_DESCR_SIZE);
318 fcode_base = (u32 *)(fimage + FUNCTION_DESCR_SIZE);
319
320 /* Code generation passes 1-2 */
321 for (pass = 1; pass < 3; pass++) {
322 /* Now build the prologue, body code & epilogue for real. */
323 cgctx.idx = 0;
324 cgctx.alt_exit_addr = 0;
325 bpf_jit_build_prologue(code_base, &cgctx);
326 if (bpf_jit_build_body(fp, code_base, fcode_base, &cgctx, addrs, pass,
327 extra_pass)) {
328 bpf_arch_text_copy(&fhdr->size, &hdr->size, sizeof(hdr->size));
329 bpf_jit_binary_pack_free(fhdr, hdr);
330 fp = org_fp;
331 goto out_addrs;
332 }
333 bpf_jit_build_epilogue(code_base, &cgctx);
334
335 if (bpf_jit_enable > 1)
336 pr_info("Pass %d: shrink = %d, seen = 0x%x\n", pass,
337 proglen - (cgctx.idx * 4), cgctx.seen);
338 }
339
340 if (bpf_jit_enable > 1)
341 /*
342 * Note that we output the base address of the code_base
343 * rather than image, since opcodes are in code_base.
344 */
345 bpf_jit_dump(flen, proglen, pass, code_base);
346
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