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Commit 3639d661 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

powerpc/64s: Un-blacklist system_call() from kprobes 



It is actually safe to probe system_call() in entry_64.S, but only till
we unset MSR_RI. To allow this, add a new symbol system_call_exit()
after the mtmsrd and blacklist that.

Suggested-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Reviewed-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 266de3a8

arch/powerpc/kernel/entry_64.S

+13 −1
Original line number Original line Diff line number Diff line
@@ -188,6 +188,18 @@ system_call: /* label this so stack traces look sane */ 
	andi.	r10,r8,MSR_RI

	andi.	r10,r8,MSR_RI

	beq-	unrecov_restore

	beq-	unrecov_restore

#endif

#endif



/*

 * This is a few instructions into the actual syscall exit path (which actually

 * starts at .Lsyscall_exit) to cater to kprobe blacklisting and to reduce the

 * number of visible symbols for profiling purposes.

 *

 * We can probe from system_call until this point as MSR_RI is set. But once it

 * is cleared below, we won't be able to take a trap.

 *

 * This is blacklisted from kprobes further below with _ASM_NOKPROBE_SYMBOL().

 */

system_call_exit:

	/*

	/*

	 * Disable interrupts so current_thread_info()->flags can't change,

	 * Disable interrupts so current_thread_info()->flags can't change,

	 * and so that we don't get interrupted after loading SRR0/1.

	 * and so that we don't get interrupted after loading SRR0/1.
@@ -414,7 +426,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR) 
	b	.	/* prevent speculative execution */

	b	.	/* prevent speculative execution */

#endif

#endif

_ASM_NOKPROBE_SYMBOL(system_call_common);

_ASM_NOKPROBE_SYMBOL(system_call_common);

_ASM_NOKPROBE_SYMBOL(system_call);

_ASM_NOKPROBE_SYMBOL(system_call_exit);





/* Save non-volatile GPRs, if not already saved. */

/* Save non-volatile GPRs, if not already saved. */

_GLOBAL(save_nvgprs)

_GLOBAL(save_nvgprs)