Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit ea678ac6 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

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



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: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 6da6c0db

arch/powerpc/include/asm/paca.h

+1 −0
Original line number Diff line number Diff line
@@ -223,6 +223,7 @@ struct paca_struct { 
	u8 hmi_event_available;		/* HMI event is available */

	u8 hmi_p9_special_emu;		/* HMI P9 special emulation */

#endif

	u8 ftrace_enabled;		/* Hard disable ftrace */



	/* Stuff for accurate time accounting */

	struct cpu_accounting_data accounting;

arch/powerpc/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/powerpc/kernel/setup_64.c

+3 −0
Original line number Diff line number Diff line
@@ -252,6 +252,9 @@ static void cpu_ready_for_interrupts(void) 


	/* Set IR and DR in PACA MSR */

	get_paca()->kernel_msr = MSR_KERNEL;



	/* We are now ok to enable ftrace */

	get_paca()->ftrace_enabled = 1;

}



unsigned long spr_default_dscr = 0;

arch/powerpc/kernel/trace/ftrace_64_mprofile.S

+14 −0
Original line number Diff line number Diff line
@@ -47,6 +47,12 @@ _GLOBAL(ftrace_caller) 
	/* Save all gprs to pt_regs */

	SAVE_GPR(0, r1)

	SAVE_10GPRS(2, r1)



	/* Ok to continue? */

	lbz	r3, PACA_FTRACE_ENABLED(r13)

	cmpdi	r3, 0

	beq	ftrace_no_trace



	SAVE_10GPRS(12, r1)

	SAVE_10GPRS(22, r1)
@@ -168,6 +174,14 @@ _GLOBAL(ftrace_graph_stub) 
_GLOBAL(ftrace_stub)

	blr



ftrace_no_trace:

	mflr	r3

	mtctr	r3

	REST_GPR(3, r1)

	addi	r1, r1, SWITCH_FRAME_SIZE

	mtlr	r0

	bctr



#ifdef CONFIG_LIVEPATCH

	/*

	 * This function runs in the mcount context, between two functions. As

arch/powerpc/kernel/trace/ftrace_64_pg.S

+4 −0
Original line number Diff line number Diff line
@@ -16,6 +16,10 @@ 


#ifdef CONFIG_DYNAMIC_FTRACE

_GLOBAL_TOC(ftrace_caller)

	lbz	r3, PACA_FTRACE_ENABLED(r13)

	cmpdi	r3, 0

	beqlr



	/* Taken from output of objdump from lib64/glibc */

	mflr	r3

	ld	r11, 0(r1)