s390/ftrace: fix arch_ftrace_get_regs implementation

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>

diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index 267f70f..6f80ec9 100644 (file)
--- 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;
 }
 
 /*

diff --git a/arch/s390/include/asm/ptrace.h b/arch/s390/include/asm/ptrace.h
index 4ffa8e7..ddb70fb 100644 (file)
--- 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__
 

diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 5026d21..89c0870 100644 (file)
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -326,7 +326,7 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
 
        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()) {

diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index 39bcc0e..a24177d 100644 (file)
--- 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