From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-98.freemail.mail.aliyun.com (out30-98.freemail.mail.aliyun.com [115.124.30.98]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 33B6A1925BC; Thu, 28 May 2026 08:23:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.98 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779956608; cv=none; b=rXjdwQA6O2CrEEo8n9PjM/uMTJqGe2uFQqSKU2gPwimte0UqOIilw3GFGUMlALWIaWgCEdmV4WWaJZKaQ6lmzDCrcMYsPzXctp/LAalyErVFmucafA0atJiI8axtAU6Xfg+ERsr4JKPgbz4+NRJQXmptZiR99JrqMlOlIlaN11g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779956608; c=relaxed/simple; bh=+zdF7Wz1qSIbzWTC+Qaz5AvlBWMIhZZ0AbLYqA69WVM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Q3xFPXzs32Bf2Y3vYxaDBztFhRI9YDbGdN9+/UsgsKBPVvjuKUIC0SCA5Zn6dSUsR72LeY9md4tM6AYTieknykkM+L/vM82K6JS7TR7uUo6A/3KA4YaE+5gtztf+40XPcj14bRzaL8LTntuUYg9U52mErrOkrkJdPl6OcYkAqxY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=A8sNj5sV; arc=none smtp.client-ip=115.124.30.98 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="A8sNj5sV" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1779956596; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=hx/IyZLsW3yP4Odj5A1dY32lM9lXE7p/KdxI82QGF2I=; b=A8sNj5sVdQUKdJZyc52ek4L8WEJdPaqKIERckZPyiYNFgZrBR0zyQdN+Mnw2YWYWf+bMtnSu08ib6E8sUIXYj40ZmpVXN9kBl/J5Gqq8HKcs7qBhBsKQJQh8XTcJULwW2GElE3hjbldSZjiNWxII9fGegDGUVH1TMyLte4k+NNw= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R321e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045098064;MF=wanghan@linux.alibaba.com;NM=1;PH=DS;RN=34;SR=0;TI=SMTPD_---0X3lxQM3_1779956593; Received: from wanghan-Workstation..(mailfrom:wanghan@linux.alibaba.com fp:SMTPD_---0X3lxQM3_1779956593 cluster:ay36) by smtp.aliyun-inc.com; Thu, 28 May 2026 16:23:14 +0800 From: Wang Han To: Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: Steven Rostedt , Alexandre Ghiti , Masami Hiramatsu , Mark Rutland , Catalin Marinas , Chen Pei , Andy Chiu , =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= , Deepak Gupta , Puranjay Mohan , Conor Dooley , Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , Shuah Khan , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , oliver.yang@linux.alibaba.com, xueshuai@linux.alibaba.com, zhuo.song@linux.alibaba.com, jkchen@linux.alibaba.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, live-patching@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH v2 1/8] scripts/sorttable: Handle RISC-V patchable ftrace entries Date: Thu, 28 May 2026 16:23:03 +0800 Message-ID: <20260528082310.1994388-2-wanghan@linux.alibaba.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260527123530.2593918-1-wanghan@linux.alibaba.com> References: <20260527123530.2593918-1-wanghan@linux.alibaba.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit RISC-V uses -fpatchable-function-entry=8,4 when the compressed ISA is enabled and -fpatchable-function-entry=4,2 otherwise. In both cases, the patchable NOP area starts 8 bytes before the function symbol address. The __mcount_loc entries therefore point at the patchable NOP area associated with a function, while nm reports the function symbol at the entry address used for the function range check. After RISC-V selected HAVE_BUILDTIME_MCOUNT_SORT, sorttable started applying that range check at build time. Without allowing entries just before the reported function address, the mcount sorter treats valid RISC-V ftrace callsites as invalid weak-function entries and writes them back as zero. The resulting kernel boots with no ftrace entries, breaking dynamic ftrace and users such as livepatch. The failure is silent during the final link because zeroing weak-function entries is an expected sorttable operation. At boot, those zero entries are skipped by ftrace_process_locs(), so the only obvious symptom is that the vmlinux ftrace table has lost valid callsites and ftrace users cannot attach to them. CONFIG_FTRACE_SORT_STARTUP_TEST also reports the table as sorted in this state: it only checks that the __mcount_loc entries are in ascending order, which a fully zeroed table trivially satisfies. The original commit relied on this check and did not see the regression. On an affected RISC-V QEMU boot with both CONFIG_FTRACE_SORT_STARTUP_TEST and CONFIG_FTRACE_STARTUP_TEST enabled, the sort check still passes while ftrace reports zero usable entries and the early selftests fail: [ 0.000000] ftrace section at ffffffff8101da98 sorted properly [ 0.000000] ftrace: allocating 0 entries in 128 pages [ 0.054999] Testing tracer function: .. no entries found ..FAILED! [ 0.172407] tracer: function failed selftest, disabling [ 0.178186] Failed to init function_graph tracer, init returned -19 Handle RISC-V like arm64 for the function-range check and allow patchable entries up to 8 bytes before the function address. With this fix, a RISC-V QEMU smoke boot with ftrace startup tests shows the vmlinux ftrace table is populated and dynamic ftrace still works: [ 0.000000] ftrace: allocating 46749 entries in 184 pages [ 0.051115] Testing tracer function: PASSED [ 1.283782] Testing dynamic ftrace: PASSED [ 6.275456] Testing tracer function_graph: PASSED Fixes: 0ca1724b56af ("riscv: ftrace: select HAVE_BUILDTIME_MCOUNT_SORT") Suggested-by: Steven Rostedt (Google) Link: https://lore.kernel.org/all/20260527113028.4b21a5de@fedora/ Signed-off-by: Wang Han --- scripts/sorttable.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/scripts/sorttable.c b/scripts/sorttable.c index e8ed11c680c6..4c10e85bb5af 100644 --- a/scripts/sorttable.c +++ b/scripts/sorttable.c @@ -891,17 +891,21 @@ static int do_file(char const *const fname, void *addr) table_sort_t custom_sort = NULL; switch (elf_map_machine(ehdr)) { - case EM_AARCH64: #ifdef MCOUNT_SORT_ENABLED + case EM_AARCH64: sort_reloc = true; rela_type = 0x403; - /* arm64 uses patchable function entry placing before function */ + /* fallthrough */ + case EM_RISCV: + /* arm64 and RISC-V place patchable entries before the function */ before_func = 8; +#else + case EM_AARCH64: + case EM_RISCV: #endif /* fallthrough */ case EM_386: case EM_LOONGARCH: - case EM_RISCV: case EM_S390: case EM_X86_64: custom_sort = sort_relative_table_with_data; -- 2.43.0