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powerpc64/ftrace: Add a field in paca to disable ftrace in unsafe code paths

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We have some C code that we call into from real mode where we cannot
take any exceptions. Though the C functions themselves are mostly safe,
if these functions are traced, there is a possibility that we may take
an exception. For instance, in certain conditions, the ftrace code uses
WARN(), which uses a 'trap' to do its job.

For such scenarios, introduce a new field in paca 'ftrace_enabled',
which is checked on ftrace entry before continuing. This field can then
be set to zero to disable/pause ftrace, and set to a non-zero value to
resume ftrace.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Naveen N. Rao
2018-04-19 12:34:00 +05:30
committed by Michael Ellerman
parent 6da6c0db53
commit ea678ac627
5 changed files with 23 additions and 0 deletions
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1
arch/powerpc/kernel/asm-offsets.c
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@@ -180,6 +180,7 @@ int main(void)
OFFSET(PACAKMSR, paca_struct, kernel_msr);
OFFSET(PACAIRQSOFTMASK, paca_struct, irq_soft_mask);
OFFSET(PACAIRQHAPPENED, paca_struct, irq_happened);
OFFSET(PACA_FTRACE_ENABLED, paca_struct, ftrace_enabled);
#ifdef CONFIG_PPC_BOOK3S
OFFSET(PACACONTEXTID, paca_struct, mm_ctx_id);
#ifdef CONFIG_PPC_MM_SLICES