s390/tracing: Enable HAVE_FTRACE_GRAPH_FUNC

Add ftrace_graph_func() which is required for fprobe to access registers.
This also eliminates the need for calling prepare_ftrace_return() from
ftrace_caller().

Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: bpf <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/173519002875.391279.7060964632119674159.stgit@devnote2
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index d8eee56c10b61a6e57cbf5cedf7ee6ff70f2d655..622ea2e9a87ecddb462a48d894d2e4c8fe7c1ca6 100644 (file)
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -190,6 +190,7 @@ config S390
        select HAVE_EFFICIENT_UNALIGNED_ACCESS
        select HAVE_GUP_FAST
        select HAVE_FENTRY
+       select HAVE_FTRACE_GRAPH_FUNC
        select HAVE_FTRACE_MCOUNT_RECORD
        select HAVE_FUNCTION_ARG_ACCESS_API
        select HAVE_FUNCTION_ERROR_INJECTION

diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h
index 5b7cb49c41ee0c60a5b42fb17349463796cbf73b..fd3f0fe9f7b32650eeb47f59e845b5e33c1b76e1 100644 (file)
--- a/arch/s390/include/asm/ftrace.h
+++ b/arch/s390/include/asm/ftrace.h
@@ -39,6 +39,7 @@ struct dyn_arch_ftrace { };
 
 struct module;
 struct dyn_ftrace;
+struct ftrace_ops;
 
 bool ftrace_need_init_nop(void);
 #define ftrace_need_init_nop ftrace_need_init_nop
@@ -122,6 +123,10 @@ static inline bool arch_syscall_match_sym_name(const char *sym,
        return !strcmp(sym + 7, name) || !strcmp(sym + 8, name);
 }
 
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+                      struct ftrace_ops *op, struct ftrace_regs *fregs);
+#define ftrace_graph_func ftrace_graph_func
+
 #endif /* __ASSEMBLY__ */
 
 #ifdef CONFIG_FUNCTION_TRACER

diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h
index 21969520f947d42a3d631bc59d8c4786853eb6ee..a1f28879c87e27d3edb3708e1c69ec60fc609445 100644 (file)
--- a/arch/s390/kernel/entry.h
+++ b/arch/s390/kernel/entry.h
@@ -41,7 +41,6 @@ void do_restart(void *arg);
 void __init startup_init(void);
 void die(struct pt_regs *regs, const char *str);
 int setup_profiling_timer(unsigned int multiplier);
-unsigned long prepare_ftrace_return(unsigned long parent, unsigned long sp, unsigned long ip);
 
 struct s390_mmap_arg_struct;
 struct fadvise64_64_args;

diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 51439a71e392c64e0c9ed0a9ca25ba4407788689..c0b2c97efefb8cc810f740be0c6a2183d68ce535 100644 (file)
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -261,43 +261,23 @@ void ftrace_arch_code_modify_post_process(void)
 }
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
-/*
- * Hook the return address and push it in the stack of return addresses
- * in current thread info.
- */
-unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
-                                   unsigned long ip)
-{
-       if (unlikely(ftrace_graph_is_dead()))
-               goto out;
-       if (unlikely(atomic_read(&current->tracing_graph_pause)))
-               goto out;
-       ip -= MCOUNT_INSN_SIZE;
-       if (!function_graph_enter(ra, ip, 0, (void *) sp))
-               ra = (unsigned long) return_to_handler;
-out:
-       return ra;
-}
-NOKPROBE_SYMBOL(prepare_ftrace_return);
 
-/*
- * Patch the kernel code at ftrace_graph_caller location. The instruction
- * there is branch relative on condition. To enable the ftrace graph code
- * block, we simply patch the mask field of the instruction to zero and
- * turn the instruction into a nop.
- * To disable the ftrace graph code the mask field will be patched to
- * all ones, which turns the instruction into an unconditional branch.
- */
-int ftrace_enable_ftrace_graph_caller(void)
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+                      struct ftrace_ops *op, struct ftrace_regs *fregs)
 {
-       /* Expect brc 0xf,... */
-       return ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false);
-}
+       unsigned long *parent = &arch_ftrace_regs(fregs)->regs.gprs[14];
+       int bit;
 
-int ftrace_disable_ftrace_graph_caller(void)
-{
-       /* Expect brc 0x0,... */
-       return ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true);
+       if (unlikely(ftrace_graph_is_dead()))
+               return;
+       if (unlikely(atomic_read(&current->tracing_graph_pause)))
+               return;
+       bit = ftrace_test_recursion_trylock(ip, *parent);
+       if (bit < 0)
+               return;
+       if (!function_graph_enter_regs(*parent, ip, 0, parent, fregs))
+               *parent = (unsigned long)&return_to_handler;
+       ftrace_test_recursion_unlock(bit);
 }
 
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */

diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S
index 2b628aa3d8095419f6a828e0709e6ff10b74285a..1fec370fecf481deebb5dc9a5defa68a5a0d74b7 100644 (file)
--- a/arch/s390/kernel/mcount.S
+++ b/arch/s390/kernel/mcount.S
@@ -104,17 +104,6 @@ SYM_CODE_START(ftrace_common)
        lgr     %r3,%r14
        la      %r5,STACK_FREGS(%r15)
        BASR_EX %r14,%r1
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-# The j instruction gets runtime patched to a nop instruction.
-# See ftrace_enable_ftrace_graph_caller.
-SYM_INNER_LABEL(ftrace_graph_caller, SYM_L_GLOBAL)
-       j       .Lftrace_graph_caller_end
-       lmg     %r2,%r3,(STACK_FREGS_PTREGS_GPRS+14*8)(%r15)
-       lg      %r4,(STACK_FREGS_PTREGS_PSW+8)(%r15)
-       brasl   %r14,prepare_ftrace_return
-       stg     %r2,(STACK_FREGS_PTREGS_GPRS+14*8)(%r15)
-.Lftrace_graph_caller_end:
-#endif
        lg      %r0,(STACK_FREGS_PTREGS_PSW+8)(%r15)
 #ifdef MARCH_HAS_Z196_FEATURES
        ltg     %r1,STACK_FREGS_PTREGS_ORIG_GPR2(%r15)