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Commit 2f59be5b authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

powerpc/ftrace: Restore LR from pt_regs 



Pass the real LR to the ftrace handler. This is needed for KPROBES_ON_FTRACE for
the pre handlers.

Also, with KPROBES_ON_FTRACE, the link register may be updated by the pre
handlers or by a registed kretprobe. Honor updated LR by restoring it from
pt_regs, rather than from the stack save area.

Live patch and function graph continue to work fine with this change.

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 22d8b3de

arch/powerpc/kernel/entry_64.S

+7 −6
Original line number Diff line number Diff line
@@ -1248,9 +1248,10 @@ _GLOBAL(ftrace_caller) 


	/* Get the _mcount() call site out of LR */

	mflr	r7

	/* Save it as pt_regs->nip & pt_regs->link */

	/* Save it as pt_regs->nip */

	std     r7, _NIP(r1)

	std     r7, _LINK(r1)

	/* Save the read LR in pt_regs->link */

	std     r0, _LINK(r1)



	/* Save callee's TOC in the ABI compliant location */

	std	r2, 24(r1)
@@ -1297,16 +1298,16 @@ ftrace_call: 
	REST_8GPRS(16,r1)

	REST_8GPRS(24,r1)



	/* Restore possibly modified LR */

	ld	r0, _LINK(r1)

	mtlr	r0



	/* Restore callee's TOC */

	ld	r2, 24(r1)



	/* Pop our stack frame */

	addi r1, r1, SWITCH_FRAME_SIZE



	/* Restore original LR for return to B */

	ld	r0, LRSAVE(r1)

	mtlr	r0



#ifdef CONFIG_LIVEPATCH

        /* Based on the cmpd above, if the NIP was altered handle livepatch */

	bne-	livepatch_handler