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06526daaff
- Fix allocation of idle shadow stack allocation during hotplug
If function graph tracing is started when a CPU is offline, if it were
come online during the trace then the idle task that represents the CPU
will not get a shadow stack allocated for it. This means all function
graph hooks that happen while that idle task is running (including in
interrupt mode) will have all its events dropped.
Switch over to the CPU hotplug mechanism that will have any newly
brought on line CPU get a callback that can allocate the shadow stack
for its idle task.
- Fix allocation size of the ret_stack_list array
When function graph tracing converted over to allowing more than one
user at a time, it had to convert its shadow stack from an array of
ret_stack structures to an array of unsigned longs. The shadow stacks
are allocated in batches of 32 at a time and assigned to every running
task. The batch is held by the ret_stack_list array. But when the
conversion happened, instead of allocating an array of 32 pointers, it
was allocated as a ret_stack itself (PAGE_SIZE). This ret_stack_list
gets passed to a function that iterates over what it believes is its
size defined by the FTRACE_RETSTACK_ALLOC_SIZE macro (which is 32).
Luckily (PAGE_SIZE) is greater than 32 * sizeof(long), otherwise this
would have been an array overflow. This still should be fixed and the
ret_stack_list should be allocated to the size it is expected to be as
someday it may end up being bigger than SHADOW_STACK_SIZE.
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Merge tag 'ftrace-v6.12-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull ftrace fixes from Steven Rostedt:
"A couple of fixes to function graph infrastructure:
- Fix allocation of idle shadow stack allocation during hotplug
If function graph tracing is started when a CPU is offline, if it
were come online during the trace then the idle task that
represents the CPU will not get a shadow stack allocated for it.
This means all function graph hooks that happen while that idle
task is running (including in interrupt mode) will have all its
events dropped.
Switch over to the CPU hotplug mechanism that will have any newly
brought on line CPU get a callback that can allocate the shadow
stack for its idle task.
- Fix allocation size of the ret_stack_list array
When function graph tracing converted over to allowing more than
one user at a time, it had to convert its shadow stack from an
array of ret_stack structures to an array of unsigned longs. The
shadow stacks are allocated in batches of 32 at a time and assigned
to every running task. The batch is held by the ret_stack_list
array.
But when the conversion happened, instead of allocating an array of
32 pointers, it was allocated as a ret_stack itself (PAGE_SIZE).
This ret_stack_list gets passed to a function that iterates over
what it believes is its size defined by the
FTRACE_RETSTACK_ALLOC_SIZE macro (which is 32).
Luckily (PAGE_SIZE) is greater than 32 * sizeof(long), otherwise
this would have been an array overflow. This still should be fixed
and the ret_stack_list should be allocated to the size it is
expected to be as someday it may end up being bigger than
SHADOW_STACK_SIZE"
* tag 'ftrace-v6.12-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
fgraph: Allocate ret_stack_list with proper size
fgraph: Use CPU hotplug mechanism to initialize idle shadow stacks
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