[PATCH 1/4] s390/ftrace: add HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALL support

Heiko Carstens
2021-10-12T13:39:07Z

This is the s390 variant of commit 562955fe6a55 ("ftrace/x86: Add
register_ftrace_direct() for custom trampolines").

Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
arch/s390/Kconfig | 1 +
arch/s390/include/asm/ftrace.h | 12 ++++++++++++
arch/s390/kernel/mcount.S | 23 +++++++++++++++++------
3 files changed, 30 insertions(+), 6 deletions(-)

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 87b71b91e5c9..908da6f1aa0d 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -153,6 +153,7 @@ config S390
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_ARGS
+ select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
select HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EBPF_JIT if PACK_STACK && HAVE_MARCH_Z196_FEATURES
select HAVE_EFFICIENT_UNALIGNED_ACCESS
diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index 4a721b44d4f4..267f70f4393f 100644
--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -58,6 +58,18 @@ static __always_inline void ftrace_instruction_pointer_set(struct ftrace_regs *f
regs->psw.addr = ip;
}

+/*
+ * When an ftrace registered caller is tracing a function that is
+ * also set by a register_ftrace_direct() call, it needs to be
+ * differentiated in the ftrace_caller trampoline. To do this,
+ * place the direct caller in the ORIG_GPR2 part of pt_regs. This
+ * tells the ftrace_caller that there's a direct caller.
+ */
+static inline void arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr)
+{
+ regs->orig_gpr2 = addr;
+}
+
/*
* Even though the system call numbers are identical for s390/s390x a
* different system call table is used for compat tasks. This may lead
diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index cc25fbd75ea9..39bcc0e39a10 100644
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -22,10 +22,11 @@ ENTRY(ftrace_stub)
BR_EX %r14
ENDPROC(ftrace_stub)

-#define STACK_FRAME_SIZE (STACK_FRAME_OVERHEAD + __PT_SIZE)
-#define STACK_PTREGS (STACK_FRAME_OVERHEAD)
-#define STACK_PTREGS_GPRS (STACK_PTREGS + __PT_GPRS)
-#define STACK_PTREGS_PSW (STACK_PTREGS + __PT_PSW)
+#define STACK_FRAME_SIZE (STACK_FRAME_OVERHEAD + __PT_SIZE)
+#define STACK_PTREGS (STACK_FRAME_OVERHEAD)
+#define STACK_PTREGS_GPRS (STACK_PTREGS + __PT_GPRS)
+#define STACK_PTREGS_PSW (STACK_PTREGS + __PT_PSW)
+#define STACK_PTREGS_ORIG_GPR2 (STACK_PTREGS + __PT_ORIG_GPR2)
#ifdef __PACK_STACK
/* allocate just enough for r14, r15 and backchain */
#define TRACED_FUNC_FRAME_SIZE 24
@@ -51,6 +52,7 @@ ENDPROC(ftrace_stub)
# allocate pt_regs and stack frame for ftrace_trace_function
aghi %r15,-STACK_FRAME_SIZE
stg %r1,(STACK_PTREGS_GPRS+15*8)(%r15)
+ xc STACK_PTREGS_ORIG_GPR2(8,%r15),STACK_PTREGS_ORIG_GPR2(%r15)

.if \allregs == 1
stg %r14,(STACK_PTREGS_PSW)(%r15)
@@ -101,8 +103,17 @@ SYM_INNER_LABEL(ftrace_graph_caller, SYM_L_GLOBAL)
stg %r2,(STACK_PTREGS_GPRS+14*8)(%r15)
.Lftrace_graph_caller_end:
#endif
- lg %r1,(STACK_PTREGS_PSW+8)(%r15)
- lmg %r2,%r15,(STACK_PTREGS_GPRS+2*8)(%r15)
+ lg %r0,(STACK_PTREGS_PSW+8)(%r15)
+#ifdef CONFIG_HAVE_MARCH_Z196_FEATURES
+ ltg %r1,STACK_PTREGS_ORIG_GPR2(%r15)
+ locgrz %r1,%r0
+#else
+ lg %r1,STACK_PTREGS_ORIG_GPR2(%r15)
+ ltgr %r1,%r1
+ jnz 0f
+ lgr %r1,%r0
+#endif
+0: lmg %r2,%r15,(STACK_PTREGS_GPRS+2*8)(%r15)
BR_EX %r1
SYM_CODE_END(ftrace_common)

--
2.25.1