@@ -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;
@@ -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
@@ -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;
@@ -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
@@ -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)
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> --- arch/powerpc/include/asm/paca.h | 1 + arch/powerpc/kernel/asm-offsets.c | 1 + arch/powerpc/kernel/setup_64.c | 3 +++ arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 14 ++++++++++++++ arch/powerpc/kernel/trace/ftrace_64_pg.S | 4 ++++ 5 files changed, 23 insertions(+)