From c39bd0df25b4760806e7e63d79b5407d9d098158 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Tue, 14 Jan 2025 13:57:58 -0800 Subject: [PATCH 1/2] objtool: Ignore dangling jump table entries [ Upstream commit 3724062ca2b1364f02cf44dbea1a552227844ad1 ] Clang sometimes leaves dangling unused jump table entries which point to the end of the function. Ignore them. Closes: https://lore.kernel.org/20250113235835.vqgvb7cdspksy5dn@jpoimboe Reported-by: Klaus Kusche Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/ee25c0b7e80113e950bd1d4c208b671d35774ff4.1736891751.git.jpoimboe@kernel.org Signed-off-by: Sasha Levin --- tools/objtool/check.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 1691aa6e6ce3..3c3e5760e81b 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2061,6 +2061,14 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn, reloc_addend(reloc) == pfunc->offset) break; + /* + * Clang sometimes leaves dangling unused jump table entries + * which point to the end of the function. Ignore them. + */ + if (reloc->sym->sec == pfunc->sec && + reloc_addend(reloc) == pfunc->offset + pfunc->len) + goto next; + dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc)); if (!dest_insn) break; @@ -2078,6 +2086,7 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn, alt->insn = dest_insn; alt->next = insn->alts; insn->alts = alt; +next: prev_offset = reloc_offset(reloc); } From 30a40b59259443035b3450cd8b562e586a446d14 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Wed, 29 Jan 2025 20:53:03 +0100 Subject: [PATCH 2/2] sched: Clarify wake_up_q()'s write to task->wake_q.next [ Upstream commit bcc6244e13b4d4903511a1ea84368abf925031c0 ] Clarify that wake_up_q() does an atomic write to task->wake_q.next, after which a concurrent __wake_q_add() can immediately overwrite task->wake_q.next again. Signed-off-by: Jann Horn Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20250129-sched-wakeup-prettier-v1-1-2f51f5f663fa@google.com Signed-off-by: Sasha Levin --- kernel/sched/core.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9803f10a082a..1f817d0c5d2d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1058,9 +1058,10 @@ void wake_up_q(struct wake_q_head *head) struct task_struct *task; task = container_of(node, struct task_struct, wake_q); - /* Task can safely be re-inserted now: */ node = node->next; - task->wake_q.next = NULL; + /* pairs with cmpxchg_relaxed() in __wake_q_add() */ + WRITE_ONCE(task->wake_q.next, NULL); + /* Task can safely be re-inserted now. */ /* * wake_up_process() executes a full barrier, which pairs with