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Subject[PATCH 5.16 184/186] s390/ftrace: fix arch_ftrace_get_regs implementation
Date
From: Heiko Carstens <hca@linux.ibm.com>

commit 1389f17937a03fe4ec71b094e1aa6530a901963e upstream.

arch_ftrace_get_regs is supposed to return a struct pt_regs pointer
only if the pt_regs structure contains all register contents, which
means it must have been populated when created via ftrace_regs_caller.

If it was populated via ftrace_caller the contents are not complete
(the psw mask part is missing), and therefore a NULL pointer needs be
returned.

The current code incorrectly always returns a struct pt_regs pointer.

Fix this by adding another pt_regs flag which indicates if the
contents are complete, and fix arch_ftrace_get_regs accordingly.

Fixes: 894979689d3a ("s390/ftrace: provide separate ftrace_caller/ftrace_regs_caller implementations")
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reported-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/s390/include/asm/ftrace.h | 10 ++++++----
arch/s390/include/asm/ptrace.h | 2 ++
arch/s390/kernel/ftrace.c | 2 +-
arch/s390/kernel/mcount.S | 9 +++++++++
4 files changed, 18 insertions(+), 5 deletions(-)

--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -47,15 +47,17 @@ struct ftrace_regs {

static __always_inline struct pt_regs *arch_ftrace_get_regs(struct ftrace_regs *fregs)
{
- return &fregs->regs;
+ struct pt_regs *regs = &fregs->regs;
+
+ if (test_pt_regs_flag(regs, PIF_FTRACE_FULL_REGS))
+ return regs;
+ return NULL;
}

static __always_inline void ftrace_instruction_pointer_set(struct ftrace_regs *fregs,
unsigned long ip)
{
- struct pt_regs *regs = arch_ftrace_get_regs(fregs);
-
- regs->psw.addr = ip;
+ fregs->regs.psw.addr = ip;
}

/*
--- a/arch/s390/include/asm/ptrace.h
+++ b/arch/s390/include/asm/ptrace.h
@@ -15,11 +15,13 @@
#define PIF_EXECVE_PGSTE_RESTART 1 /* restart execve for PGSTE binaries */
#define PIF_SYSCALL_RET_SET 2 /* return value was set via ptrace */
#define PIF_GUEST_FAULT 3 /* indicates program check in sie64a */
+#define PIF_FTRACE_FULL_REGS 4 /* all register contents valid (ftrace) */

#define _PIF_SYSCALL BIT(PIF_SYSCALL)
#define _PIF_EXECVE_PGSTE_RESTART BIT(PIF_EXECVE_PGSTE_RESTART)
#define _PIF_SYSCALL_RET_SET BIT(PIF_SYSCALL_RET_SET)
#define _PIF_GUEST_FAULT BIT(PIF_GUEST_FAULT)
+#define _PIF_FTRACE_FULL_REGS BIT(PIF_FTRACE_FULL_REGS)

#ifndef __ASSEMBLY__

--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -291,7 +291,7 @@ void kprobe_ftrace_handler(unsigned long

regs = ftrace_get_regs(fregs);
p = get_kprobe((kprobe_opcode_t *)ip);
- if (unlikely(!p) || kprobe_disabled(p))
+ if (!regs || unlikely(!p) || kprobe_disabled(p))
goto out;

if (kprobe_running()) {
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -27,6 +27,7 @@ ENDPROC(ftrace_stub)
#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)
+#define STACK_PTREGS_FLAGS (STACK_PTREGS + __PT_FLAGS)
#ifdef __PACK_STACK
/* allocate just enough for r14, r15 and backchain */
#define TRACED_FUNC_FRAME_SIZE 24
@@ -57,6 +58,14 @@ ENDPROC(ftrace_stub)
.if \allregs == 1
stg %r14,(STACK_PTREGS_PSW)(%r15)
stosm (STACK_PTREGS_PSW)(%r15),0
+#ifdef CONFIG_HAVE_MARCH_Z10_FEATURES
+ mvghi STACK_PTREGS_FLAGS(%r15),_PIF_FTRACE_FULL_REGS
+#else
+ lghi %r14,_PIF_FTRACE_FULL_REGS
+ stg %r14,STACK_PTREGS_FLAGS(%r15)
+#endif
+ .else
+ xc STACK_PTREGS_FLAGS(8,%r15),STACK_PTREGS_FLAGS(%r15)
.endif

lg %r14,(__SF_GPRS+8*8)(%r1) # restore original return address

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