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authorPratyush Anand <panand@redhat.com>2018-02-05 16:28:01 +0300
committerCatalin Marinas <catalin.marinas@arm.com>2018-02-23 16:46:38 +0300
commit9f416319f40cd857d2bb517630e5855a905ef3fb (patch)
tree9383e2869b1b0722fee5a033115a4dac57c691b5
parent15122ee2c515a253b0c66a3e618bc7ebe35105eb (diff)
downloadlinux-9f416319f40cd857d2bb517630e5855a905ef3fb.tar.xz
arm64: fix unwind_frame() for filtered out fn for function graph tracing
do_task_stat() calls get_wchan(), which further does unwind_frame(). unwind_frame() restores frame->pc to original value in case function graph tracer has modified a return address (LR) in a stack frame to hook a function return. However, if function graph tracer has hit a filtered function, then we can't unwind it as ftrace_push_return_trace() has biased the index(frame->graph) with a 'huge negative' offset(-FTRACE_NOTRACE_DEPTH). Moreover, arm64 stack walker defines index(frame->graph) as unsigned int, which can not compare a -ve number. Similar problem we can have with calling of walk_stackframe() from save_stack_trace_tsk() or dump_backtrace(). This patch fixes unwind_frame() to test the index for -ve value and restore index accordingly before we can restore frame->pc. Reproducer: cd /sys/kernel/debug/tracing/ echo schedule > set_graph_notrace echo 1 > options/display-graph echo wakeup > current_tracer ps -ef | grep -i agent Above commands result in: Unable to handle kernel paging request at virtual address ffff801bd3d1e000 pgd = ffff8003cbe97c00 [ffff801bd3d1e000] *pgd=0000000000000000, *pud=0000000000000000 Internal error: Oops: 96000006 [#1] SMP [...] CPU: 5 PID: 11696 Comm: ps Not tainted 4.11.0+ #33 [...] task: ffff8003c21ba000 task.stack: ffff8003cc6c0000 PC is at unwind_frame+0x12c/0x180 LR is at get_wchan+0xd4/0x134 pc : [<ffff00000808892c>] lr : [<ffff0000080860b8>] pstate: 60000145 sp : ffff8003cc6c3ab0 x29: ffff8003cc6c3ab0 x28: 0000000000000001 x27: 0000000000000026 x26: 0000000000000026 x25: 00000000000012d8 x24: 0000000000000000 x23: ffff8003c1c04000 x22: ffff000008c83000 x21: ffff8003c1c00000 x20: 000000000000000f x19: ffff8003c1bc0000 x18: 0000fffffc593690 x17: 0000000000000000 x16: 0000000000000001 x15: 0000b855670e2b60 x14: 0003e97f22cf1d0f x13: 0000000000000001 x12: 0000000000000000 x11: 00000000e8f4883e x10: 0000000154f47ec8 x9 : 0000000070f367c0 x8 : 0000000000000000 x7 : 00008003f7290000 x6 : 0000000000000018 x5 : 0000000000000000 x4 : ffff8003c1c03cb0 x3 : ffff8003c1c03ca0 x2 : 00000017ffe80000 x1 : ffff8003cc6c3af8 x0 : ffff8003d3e9e000 Process ps (pid: 11696, stack limit = 0xffff8003cc6c0000) Stack: (0xffff8003cc6c3ab0 to 0xffff8003cc6c4000) [...] [<ffff00000808892c>] unwind_frame+0x12c/0x180 [<ffff000008305008>] do_task_stat+0x864/0x870 [<ffff000008305c44>] proc_tgid_stat+0x3c/0x48 [<ffff0000082fde0c>] proc_single_show+0x5c/0xb8 [<ffff0000082b27e0>] seq_read+0x160/0x414 [<ffff000008289e6c>] __vfs_read+0x58/0x164 [<ffff00000828b164>] vfs_read+0x88/0x144 [<ffff00000828c2e8>] SyS_read+0x60/0xc0 [<ffff0000080834a0>] __sys_trace_return+0x0/0x4 Fixes: 20380bb390a4 (arm64: ftrace: fix a stack tracer's output under function graph tracer) Signed-off-by: Pratyush Anand <panand@redhat.com> Signed-off-by: Jerome Marchand <jmarchan@redhat.com> [catalin.marinas@arm.com: replace WARN_ON with WARN_ON_ONCE] Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
-rw-r--r--arch/arm64/include/asm/stacktrace.h2
-rw-r--r--arch/arm64/kernel/stacktrace.c5
-rw-r--r--arch/arm64/kernel/time.c2
3 files changed, 7 insertions, 2 deletions
diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 472ef944e932..902f9edacbea 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -28,7 +28,7 @@ struct stackframe {
unsigned long fp;
unsigned long pc;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
- unsigned int graph;
+ int graph;
#endif
};
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index 76809ccd309c..d5718a060672 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -59,6 +59,11 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
if (tsk->ret_stack &&
(frame->pc == (unsigned long)return_to_handler)) {
+ if (WARN_ON_ONCE(frame->graph == -1))
+ return -EINVAL;
+ if (frame->graph < -1)
+ frame->graph += FTRACE_NOTRACE_DEPTH;
+
/*
* This is a case where function graph tracer has
* modified a return address (LR) in a stack frame
diff --git a/arch/arm64/kernel/time.c b/arch/arm64/kernel/time.c
index a4391280fba9..f258636273c9 100644
--- a/arch/arm64/kernel/time.c
+++ b/arch/arm64/kernel/time.c
@@ -52,7 +52,7 @@ unsigned long profile_pc(struct pt_regs *regs)
frame.fp = regs->regs[29];
frame.pc = regs->pc;
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
- frame.graph = -1; /* no task info */
+ frame.graph = current->curr_ret_stack;
#endif
do {
int ret = unwind_frame(NULL, &frame);