{"id":2196705,"url":"http://patchwork.ozlabs.org/api/1.0/patches/2196705/?format=json","project":{"id":2,"url":"http://patchwork.ozlabs.org/api/1.0/projects/2/?format=json","name":"Linux PPC development","link_name":"linuxppc-dev","list_id":"linuxppc-dev.lists.ozlabs.org","list_email":"linuxppc-dev@lists.ozlabs.org","web_url":"https://github.com/linuxppc/wiki/wiki","scm_url":"https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git","webscm_url":"https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git/"},"msgid":"<20260216065639.1750181-6-hbathini@linux.ibm.com>","date":"2026-02-16T06:56:39","name":"[5/5] powerpc64/bpf: fix handling of BPF stack in exception callback","commit_ref":null,"pull_url":null,"state":"superseded","archived":false,"hash":"0a8995f275211dc04e387d63b19ae55e8369f353","submitter":{"id":74073,"url":"http://patchwork.ozlabs.org/api/1.0/people/74073/?format=json","name":"Hari Bathini","email":"hbathini@linux.ibm.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260216065639.1750181-6-hbathini@linux.ibm.com/mbox/","series":[{"id":492248,"url":"http://patchwork.ozlabs.org/api/1.0/series/492248/?format=json","date":"2026-02-16T06:56:34","name":"powerpc64/bpf: various fixes","version":1,"mbox":"http://patchwork.ozlabs.org/series/492248/mbox/"}],"check":"success","checks":"http://patchwork.ozlabs.org/api/patches/2196705/checks/","tags":{},"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linuxppc-dev@lists.ozlabs.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=JfQ26m2D;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=2404:9400:21b9:f100::1; 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When\nexception boundary and exception callback programs have different BPF\nstack depth, the current stack unwind in exception callback will fail.\nAdjust the stack frame size of exception callback, in its prologue,\nif its BPF stack depth is different from that of exception boundary.\n\nReported-by: bot+bpf-ci@kernel.org\nCloses: https://lore.kernel.org/bpf/2a310e86a59eb4c44c3ac9e5647814469d9c955580c9c0f1b3d9ca4a44717a34@mail.kernel.org/\nFixes: 11d45eee9f42 (\"powerpc64/bpf: Additional NVR handling for bpf_throw\")\nSigned-off-by: Hari Bathini \n---\n arch/powerpc/net/bpf_jit_comp64.c | 30 ++++++++++++++++++++++--------\n 1 file changed, 22 insertions(+), 8 deletions(-)","diff":"diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c\nindex 5d4d2bb23cef..640b84409687 100644\n--- a/arch/powerpc/net/bpf_jit_comp64.c\n+++ b/arch/powerpc/net/bpf_jit_comp64.c\n@@ -32,14 +32,15 @@\n *\n *\t\t[\tprev sp\t\t] <-------------\n *\t\t[ tail_call_info\t] 8\t\t|\n- *\t\t[ nv gpr save area\t] 6*8 + (12*8)\t|\n+ *\t\t[ nv gpr save area\t] 6*8\t\t|\n+ *\t\t[ addl. nv gpr save area] (12*8)\t| <--- exception boundary/callback program\n *\t\t[ local_tmp_var\t] 24\t\t|\n * fp (r31) -->\t[ ebpf stack space\t] upto 512\t|\n *\t\t[ frame header\t] 32/112\t|\n * sp (r1) --->\t[ stack pointer\t] --------------\n *\n * Additional (12*8) in 'nv gpr save area' only in case of\n- * exception boundary.\n+ * exception boundary/callback.\n */\n \n /* BPF non-volatile registers save area size */\n@@ -128,12 +129,13 @@ static inline bool bpf_has_stack_frame(struct codegen_context *ctx)\n *\t\t[\t ... \t] \t\t|\n * sp (r1) --->\t[ stack pointer\t] --------------\n *\t\t[ tail_call_info\t] 8\n- *\t\t[ nv gpr save area\t] 6*8 + (12*8)\n+ *\t\t[ nv gpr save area\t] 6*8\n+ *\t\t[ addl. nv gpr save area] (12*8) <--- exception boundary/callback program\n *\t\t[ local_tmp_var\t] 24\n *\t\t[ unused red zone\t] 224\n *\n * Additional (12*8) in 'nv gpr save area' only in case of\n- * exception boundary.\n+ * exception boundary/callback.\n */\n static int bpf_jit_stack_local(struct codegen_context *ctx)\n {\n@@ -240,10 +242,6 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)\n \n \tif (bpf_has_stack_frame(ctx) && !ctx->exception_cb) {\n \t\t/*\n-\t\t * exception_cb uses boundary frame after stack walk.\n-\t\t * It can simply use redzone, this optimization reduces\n-\t\t * stack walk loop by one level.\n-\t\t *\n \t\t * We need a stack frame, but we don't necessarily need to\n \t\t * save/restore LR unless we call other functions\n \t\t */\n@@ -287,6 +285,22 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx)\n \t\t * program(main prog) as third arg\n \t\t */\n \t\tEMIT(PPC_RAW_MR(_R1, _R5));\n+\t\t/*\n+\t\t * Exception callback reuses the stack frame of exception boundary.\n+\t\t * But BPF stack depth of exception callback and exception boundary\n+\t\t * don't have to be same. If BPF stack depth is different, adjust the\n+\t\t * stack frame size considering BPF stack depth of exception callback.\n+\t\t * The non-volatile register save area remains unchanged. These non-\n+\t\t * volatile registers are restored in exception callback's epilogue.\n+\t\t */\n+\t\tEMIT(PPC_RAW_LD(bpf_to_ppc(TMP_REG_1), _R5, 0));\n+\t\tEMIT(PPC_RAW_SUB(bpf_to_ppc(TMP_REG_2), _R1, bpf_to_ppc(TMP_REG_1)));\n+\t\tEMIT(PPC_RAW_ADDI(bpf_to_ppc(TMP_REG_2), bpf_to_ppc(TMP_REG_2),\n+\t\t\t-BPF_PPC_EXC_STACKFRAME));\n+\t\tEMIT(PPC_RAW_CMPLDI(bpf_to_ppc(TMP_REG_2), ctx->stack_size));\n+\t\tPPC_BCC_CONST_SHORT(COND_EQ, 12);\n+\t\tEMIT(PPC_RAW_MR(_R1, bpf_to_ppc(TMP_REG_1)));\n+\t\tEMIT(PPC_RAW_STDU(_R1, _R1, -(BPF_PPC_EXC_STACKFRAME + ctx->stack_size)));\n \t}\n \n \t/*\n","prefixes":["5/5"]}