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fgraph: Allocate ret_stack_list with proper size
The ret_stack_list is an array of ret_stack shadow stacks for the function
graph usage. When the first function graph is enabled, all tasks in the
system get a shadow stack. The ret_stack_list is a 32 element array of
pointers to these shadow stacks. It allocates the shadow stack in batches
(32 stacks at a time), assigns them to running tasks, and continues until
all tasks are covered.
When the function graph shadow stack changed from an array of
ftrace_ret_stack structures to an array of longs, the allocation of
ret_stack_list went from allocating an array of 32 elements to just a
block defined by SHADOW_STACK_SIZE. Luckily, that's defined as PAGE_SIZE
and is much more than enough to hold 32 pointers. But it is way overkill
for the amount needed to allocate.
Change the allocation of ret_stack_list back to a kcalloc() of
FTRACE_RETSTACK_ALLOC_SIZE pointers.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20241018215212.23f13f40@rorschach
Fixes: 42675b723b
("function_graph: Convert ret_stack to a series of longs")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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parent
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@ -1162,7 +1162,8 @@ static int start_graph_tracing(void)
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unsigned long **ret_stack_list;
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int ret;
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ret_stack_list = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL);
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ret_stack_list = kcalloc(FTRACE_RETSTACK_ALLOC_SIZE,
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sizeof(*ret_stack_list), GFP_KERNEL);
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if (!ret_stack_list)
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return -ENOMEM;
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