diff options
| author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2014-08-15 12:33:46 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2014-09-09 08:53:28 +0200 |
| commit | 2481a87b0250bbf429fc8cdc78331efbc44a0221 (patch) | |
| tree | 0bf818ad656c2c12bbe4bc5b7882c99826439b93 /arch/s390 | |
| parent | 0f1b1ff54b386926ef1a524e60ef89ae7738bbd5 (diff) | |
s390/ftrace: optimize function graph caller code
When the function graph tracer is disabled we can skip three additional
instructions. So let's just do this.
So if function tracing is enabled but function graph tracing is
runtime disabled, we get away with a single unconditional branch.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390')
| -rw-r--r-- | arch/s390/include/asm/ftrace.h | 1 | ||||
| -rw-r--r-- | arch/s390/kernel/ftrace.c | 24 | ||||
| -rw-r--r-- | arch/s390/kernel/mcount64.S | 15 |
3 files changed, 34 insertions, 6 deletions
diff --git a/arch/s390/include/asm/ftrace.h b/arch/s390/include/asm/ftrace.h index bf246dae136..7b8e456d76c 100644 --- a/arch/s390/include/asm/ftrace.h +++ b/arch/s390/include/asm/ftrace.h @@ -4,6 +4,7 @@ #ifndef __ASSEMBLY__ extern void _mcount(void); +extern char ftrace_graph_caller_end; struct dyn_arch_ftrace { }; diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index 54d6493c4a5..de55efa5b64 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -170,6 +170,29 @@ out: * directly after the instructions. To enable the call we calculate * the original offset to prepare_ftrace_return and put it back. */ + +#ifdef CONFIG_64BIT + +int ftrace_enable_ftrace_graph_caller(void) +{ + static unsigned short offset = 0x0002; + + return probe_kernel_write((void *) ftrace_graph_caller + 2, + &offset, sizeof(offset)); +} + +int ftrace_disable_ftrace_graph_caller(void) +{ + unsigned short offset; + + offset = ((void *) &ftrace_graph_caller_end - + (void *) ftrace_graph_caller) / 2; + return probe_kernel_write((void *) ftrace_graph_caller + 2, + &offset, sizeof(offset)); +} + +#else /* CONFIG_64BIT */ + int ftrace_enable_ftrace_graph_caller(void) { unsigned short offset; @@ -188,5 +211,6 @@ int ftrace_disable_ftrace_graph_caller(void) &offset, sizeof(offset)); } +#endif /* CONFIG_64BIT */ #endif /* CONFIG_DYNAMIC_FTRACE */ #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ diff --git a/arch/s390/kernel/mcount64.S b/arch/s390/kernel/mcount64.S index c67a8bf0fd9..5b33c83adde 100644 --- a/arch/s390/kernel/mcount64.S +++ b/arch/s390/kernel/mcount64.S @@ -32,14 +32,17 @@ ENTRY(ftrace_caller) lg %r14,0(%r14) basr %r14,%r14 #ifdef CONFIG_FUNCTION_GRAPH_TRACER +# The j instruction gets runtime patched to a nop instruction. +# See ftrace_enable_ftrace_graph_caller. The patched instruction is: +# j .+4 +ENTRY(ftrace_graph_caller) + j ftrace_graph_caller_end lg %r2,168(%r15) lg %r3,272(%r15) -ENTRY(ftrace_graph_caller) -# The bras instruction gets runtime patched to call prepare_ftrace_return. -# See ftrace_enable_ftrace_graph_caller. The patched instruction is: -# bras %r14,prepare_ftrace_return - bras %r14,0f -0: stg %r2,168(%r15) + brasl %r14,prepare_ftrace_return + stg %r2,168(%r15) +ftrace_graph_caller_end: + .globl ftrace_graph_caller_end #endif aghi %r15,160 lmg %r2,%r5,32(%r15) |