{"id":2222434,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2222434/?format=json","web_url":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260411221413.44304-3-adubey@linux.ibm.com/","project":{"id":2,"url":"http://patchwork.ozlabs.org/api/1.1/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":"<20260411221413.44304-3-adubey@linux.ibm.com>","date":"2026-04-11T22:14:10","name":"[v3,2/5] powerpc/bpf: Move out dummy_tramp_addr after Long branch stub","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"f8cbbc072399333e237aaef839ce823244e1e531","submitter":{"id":88541,"url":"http://patchwork.ozlabs.org/api/1.1/people/88541/?format=json","name":"adubey","email":"adubey@linux.ibm.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20260411221413.44304-3-adubey@linux.ibm.com/mbox/","series":[{"id":499569,"url":"http://patchwork.ozlabs.org/api/1.1/series/499569/?format=json","web_url":"http://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=499569","date":"2026-04-11T22:14:08","name":"powerpc/bpf: Add support for verifier selftest","version":3,"mbox":"http://patchwork.ozlabs.org/series/499569/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2222434/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2222434/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=i35IdX+4;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org\n (client-ip=112.213.38.117; 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This allows uninterrupted disassembly until the\nlast 8 bytes. Exclude these last bytes from the overall\nprogram length to prevent failure in assembly generation.\nAlso, align dummy_tramp_addr field with 8-byte boundary.\n\nFollowing is disassembler output for test program with moved down\ndummy_tramp_addr field:\n.....\n.....\npc:68 left:44 a6 03 08 7c : mtlr 0\npc:72 left:40 bc ff ff 4b : b .-68\npc:76 left:36 a6 02 68 7d : mflr 11\npc:80 left:32 05 00 9f 42 : bcl 20, 31, .+4\npc:84 left:28 a6 02 88 7d : mflr 12\npc:88 left:24 14 00 8c e9 : ld 12, 20(12)\npc:92 left:20 a6 03 89 7d : mtctr 12\npc:96 left:16 a6 03 68 7d : mtlr 11\npc:100 left:12 20 04 80 4e : bctr\npc:104 left:8 c0 34 1d 00 :\n\nFailure log:\nCan't disasm instruction at offset 104: c0 34 1d 00 00 00 00 c0\nDisassembly logic can truncate at 104, ignoring last 8 bytes.\n\nUpdate the dummy_tramp_addr field offset calculation from the end\nof the program to reflect its new location, for bpf_arch_text_poke()\nto update the actual trampoline's address in this field.\n\nAll BPF trampoline selftests continue to pass with this patch applied.\n\nSigned-off-by: Abhishek Dubey \n---\n arch/powerpc/net/bpf_jit_comp.c | 42 +++++++++++++++++++--------------\n 1 file changed, 24 insertions(+), 18 deletions(-)","diff":"diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c\nindex c255b30a37b0..c2ac4e355464 100644\n--- a/arch/powerpc/net/bpf_jit_comp.c\n+++ b/arch/powerpc/net/bpf_jit_comp.c\n@@ -58,20 +58,22 @@ void bpf_jit_build_fentry_stubs(u32 *image, u32 *fimage, struct codegen_context\n \t * in the fimage. The alignment NOP must appear before OOL stub,\n \t * to make ool_stub_idx & long_branch_stub_idx constant from end.\n \t *\n+\t * The dummy_tramp_addr field is placed at bottom of Long branch stub.\n+\t *\n \t * Need alignment NOP in following conditions:\n \t *\n \t * OOL stub aligned\tCONFIG_PPC_FTRACE_OUT_OF_LINE\tAlignment NOP\n-\t * Y Y N\n-\t * Y N Y\n-\t * N Y Y\n-\t * N N N\n+\t * Y Y Y\n+\t * Y N N\n+\t * N Y N\n+\t * N N Y\n \t */\n #ifdef CONFIG_PPC64\n \tif (fimage && image) {\n \t\tunsigned long pc = (unsigned long)fimage + CTX_NIA(ctx);\n \n-\t\tif (IS_ALIGNED(pc, 8) ^\n-\t\t\tIS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE))\n+\t\tif (~(IS_ALIGNED(pc, 8) ^\n+\t\t\tIS_ENABLED(CONFIG_PPC_FTRACE_OUT_OF_LINE)))\n \t\t\tEMIT(PPC_RAW_NOP());\n \t}\n #endif\n@@ -93,28 +95,29 @@ void bpf_jit_build_fentry_stubs(u32 *image, u32 *fimage, struct codegen_context\n \n \t/*\n \t * Long branch stub:\n-\t *\t.long\t // 8-byte aligned\n \t *\tmflr\tr11\n \t *\tbcl\t20,31,$+4\n-\t *\tmflr\tr12\n-\t *\tld\tr12, -8-SZL(r12)\n+\t *\tmflr\tr12\t// lr/r12 stores pc of current(this) inst.\n+\t *\tld\tr12, 20(r12) // offset(dummy_tramp_addr) from prev inst. is 20\n \t *\tmtctr\tr12\n-\t *\tmtlr\tr11 // needed to retain ftrace ABI\n+\t *\tmtlr\tr11\t// needed to retain ftrace ABI\n \t *\tbctr\n+\t *\t.long\t // 8-byte aligned\n \t */\n-\tif (image)\n-\t\t*((unsigned long *)&image[ctx->idx]) = (unsigned long)dummy_tramp;\n-\n-\tctx->idx += SZL / 4;\n \tlong_branch_stub_idx = ctx->idx;\n \tEMIT(PPC_RAW_MFLR(_R11));\n \tEMIT(PPC_RAW_BCL4());\n \tEMIT(PPC_RAW_MFLR(_R12));\n-\tEMIT(PPC_RAW_LL(_R12, _R12, -8-SZL));\n+\tEMIT(PPC_RAW_LL(_R12, _R12, 20));\n \tEMIT(PPC_RAW_MTCTR(_R12));\n \tEMIT(PPC_RAW_MTLR(_R11));\n \tEMIT(PPC_RAW_BCTR());\n \n+\tif (image)\n+\t\t*((unsigned long *)&image[ctx->idx]) = (unsigned long)dummy_tramp;\n+\n+\tctx->idx += SZL / 4;\n+\n \tif (!bpf_jit_ool_stub) {\n \t\tbpf_jit_ool_stub = (ctx->idx - ool_stub_idx) * 4;\n \t\tbpf_jit_long_branch_stub = (ctx->idx - long_branch_stub_idx) * 4;\n@@ -1155,6 +1158,7 @@ static void do_isync(void *info __maybe_unused)\n * bpf_func:\n *\t[nop|b]\tool_stub\n * 2. Out-of-line stub:\n+ *\tnop\t// optional nop for alignment\n * ool_stub:\n *\tmflr\tr0\n *\t[b|bl]\t/\n@@ -1162,14 +1166,14 @@ static void do_isync(void *info __maybe_unused)\n *\tb\tbpf_func + 4\n * 3. Long branch stub:\n * long_branch_stub:\n- *\t.long\t/\n *\tmflr\tr11\n *\tbcl\t20,31,$+4\n *\tmflr\tr12\n- *\tld\tr12, -16(r12)\n+ *\tld\tr12, 20(r12)\n *\tmtctr\tr12\n *\tmtlr\tr11 // needed to retain ftrace ABI\n *\tbctr\n+ *\t.long\t/\n *\n * dummy_tramp is used to reduce synchronization requirements.\n *\n@@ -1271,10 +1275,12 @@ int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type old_t,\n \t * 1. Update the address in the long branch stub:\n \t * If new_addr is out of range, we will have to use the long branch stub, so patch new_addr\n \t * here. Otherwise, revert to dummy_tramp, but only if we had patched old_addr here.\n+\t *\n+\t * dummy_tramp_addr moved to bottom of long branch stub.\n \t */\n \tif ((new_addr && !is_offset_in_branch_range(new_addr - ip)) ||\n \t (old_addr && !is_offset_in_branch_range(old_addr - ip)))\n-\t\tret = patch_ulong((void *)(bpf_func_end - bpf_jit_long_branch_stub - SZL),\n+\t\tret = patch_ulong((void *)(bpf_func_end - SZL), /* SZL: dummy_tramp_addr offset */\n \t\t\t\t (new_addr && !is_offset_in_branch_range(new_addr - ip)) ?\n \t\t\t\t (unsigned long)new_addr : (unsigned long)dummy_tramp);\n \tif (ret)\n","prefixes":["v3","2/5"]}