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| author | Heiko Carstens <heiko.carstens@de.ibm.com> | 2014-10-08 12:03:08 +0400 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2014-10-09 11:14:20 +0400 |
| commit | 0cccdda8d1512af4d3f6913044e8c8e58e15ef37 (patch) | |
| tree | 8e93043ede994d899a625819cb871684f2cfe1a9 /arch/s390/kernel/ftrace.c | |
| parent | 53255c9a4dade6ff2162121430d13aaadb38a69c (diff) | |
| download | linux-0cccdda8d1512af4d3f6913044e8c8e58e15ef37.tar.xz | |
s390/ftrace: simplify enabling/disabling of ftrace_graph_caller
We can simply patch the mask field within the branch relative on
condition instruction at the beginning of the ftrace_graph_caller
code block.
This makes the logic even simpler and we get rid of the displacement
calculation.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/ftrace.c')
| -rw-r--r-- | arch/s390/kernel/ftrace.c | 22 |
1 files changed, 9 insertions, 13 deletions
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index f0072125926c..51d14fe5eb9a 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -138,28 +138,24 @@ out: /* * Patch the kernel code at ftrace_graph_caller location. The instruction - * there is branch relative and save to prepare_ftrace_return. To disable - * the call to prepare_ftrace_return we patch the bras offset to point - * directly after the instructions. To enable the call we calculate - * the original offset to prepare_ftrace_return and put it back. + * 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) { - static unsigned short offset = 0x0002; + u8 op = 0x04; /* set mask field to zero */ - return probe_kernel_write((void *) ftrace_graph_caller + 2, - &offset, sizeof(offset)); + return probe_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); } int ftrace_disable_ftrace_graph_caller(void) { - unsigned short offset; + u8 op = 0xf4; /* set mask field to all ones */ - offset = ((void *) &ftrace_graph_caller_end - - (void *) ftrace_graph_caller) / 2; - return probe_kernel_write((void *) ftrace_graph_caller + 2, - &offset, sizeof(offset)); + return probe_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op)); } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ |