linux-hardening - [PATCH 7/7] arch: Fix STACKTRACE

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Message-ID: <20211008111626.455137084@infradead.org>
Date:   Fri, 08 Oct 2021 13:15:34 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     keescook@...omium.org, jannh@...gle.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
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Subject: [PATCH 7/7] arch: Fix STACKTRACE_SUPPORT

A few archs got save_stack_trace_tsk() vs in_sched_functions() wrong.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/csky/kernel/stacktrace.c  |    7 ++++++-
 arch/mips/kernel/stacktrace.c  |   27 ++++++++++++++++-----------
 arch/nds32/kernel/stacktrace.c |   21 +++++++++++----------
 3 files changed, 33 insertions(+), 22 deletions(-)

--- a/arch/csky/kernel/stacktrace.c
+++ b/arch/csky/kernel/stacktrace.c
@@ -122,12 +122,17 @@ static bool save_trace(unsigned long pc,
 	return __save_trace(pc, arg, false);
 }
 
+static bool save_trace_nosched(unsigned long pc, void *arg)
+{
+	return __save_trace(pc, arg, true);
+}
+
 /*
  * Save stack-backtrace addresses into a stack_trace buffer.
  */
 void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
 {
-	walk_stackframe(tsk, NULL, save_trace, trace);
+	walk_stackframe(tsk, NULL, save_trace_nosched, trace);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
 
--- a/arch/mips/kernel/stacktrace.c
+++ b/arch/mips/kernel/stacktrace.c
@@ -66,16 +66,7 @@ static void save_context_stack(struct st
 #endif
 }
 
-/*
- * Save stack-backtrace addresses into a stack_trace buffer.
- */
-void save_stack_trace(struct stack_trace *trace)
-{
-	save_stack_trace_tsk(current, trace);
-}
-EXPORT_SYMBOL_GPL(save_stack_trace);
-
-void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+static void __save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace, bool savesched)
 {
 	struct pt_regs dummyregs;
 	struct pt_regs *regs = &dummyregs;
@@ -88,6 +79,20 @@ void save_stack_trace_tsk(struct task_st
 		regs->cp0_epc = tsk->thread.reg31;
 	} else
 		prepare_frametrace(regs);
-	save_context_stack(trace, tsk, regs, tsk == current);
+	save_context_stack(trace, tsk, regs, savesched);
+}
+
+/*
+ * Save stack-backtrace addresses into a stack_trace buffer.
+ */
+void save_stack_trace(struct stack_trace *trace)
+{
+	__save_stack_trace_tsk(current, trace, true);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+	__save_stack_trace_tsk(tsk, trace, false);
 }
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
--- a/arch/nds32/kernel/stacktrace.c
+++ b/arch/nds32/kernel/stacktrace.c
@@ -6,25 +6,16 @@
 #include <linux/stacktrace.h>
 #include <linux/ftrace.h>
 
-void save_stack_trace(struct stack_trace *trace)
-{
-	save_stack_trace_tsk(current, trace);
-}
-EXPORT_SYMBOL_GPL(save_stack_trace);
-
-void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+static void __save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace, bool savesched)
 {
 	unsigned long *fpn;
 	int skip = trace->skip;
-	int savesched;
 	int graph_idx = 0;
 
 	if (tsk == current) {
 		__asm__ __volatile__("\tori\t%0, $fp, #0\n":"=r"(fpn));
-		savesched = 1;
 	} else {
 		fpn = (unsigned long *)thread_saved_fp(tsk);
-		savesched = 0;
 	}
 
 	while (!kstack_end(fpn) && !((unsigned long)fpn & 0x3)
@@ -50,4 +41,14 @@ void save_stack_trace_tsk(struct task_st
 		fpn = (unsigned long *)fpp;
 	}
 }
+void save_stack_trace(struct stack_trace *trace)
+{
+	__save_stack_trace_tsk(current, trace, true);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+	__save_stack_trace_tsk(tsk, trace, false);
+}
 EXPORT_SYMBOL_GPL(save_stack_trace_tsk);