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author | Michael Ellerman <mpe@ellerman.id.au> | 2016-07-19 14:48:30 +1000 |
---|---|---|
committer | Michael Ellerman <mpe@ellerman.id.au> | 2016-07-21 20:10:37 +1000 |
commit | 9d636109511a000882f8dff4eaafa874eec5ece8 (patch) | |
tree | 321f23e7a84c48b008f5996238d67e6db1dc07fd /arch/powerpc/kernel | |
parent | b1923caa6e641f3d0a93b5d045aef67ded5aef67 (diff) | |
download | linux-9d636109511a000882f8dff4eaafa874eec5ece8.tar.bz2 |
powerpc/ftrace: Separate the heuristics for checking call sites
In __ftrace_make_nop() (the 64-bit version), we have code to deal with
two ftrace ABIs. There is the original ABI, which looks mostly like a
function call, and then the mprofile-kernel ABI which is just a branch.
The code tries to handle both cases, by looking for the presence of a
load to restore the TOC pointer (PPC_INST_LD_TOC). If we detect the TOC
load, we assume the call site is for an mcount() call using the old ABI.
That means we patch the mcount() call with a b +8, to branch over the
TOC load.
However if the kernel was built with mprofile-kernel, then there will
never be a call site using the original ftrace ABI. If for some reason
we do see a TOC load, then it's there for a good reason, and we should
not jump over it.
So split the code, using the existing CC_USING_MPROFILE_KERNEL. Kernels
built with mprofile-kernel will only look for, and expect, the new ABI,
and similarly for the original ABI.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/kernel')
-rw-r--r-- | arch/powerpc/kernel/ftrace.c | 35 |
1 files changed, 18 insertions, 17 deletions
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c index 7af6c4de044b..cc52d9795f88 100644 --- a/arch/powerpc/kernel/ftrace.c +++ b/arch/powerpc/kernel/ftrace.c @@ -144,6 +144,21 @@ __ftrace_make_nop(struct module *mod, return -EINVAL; } +#ifdef CC_USING_MPROFILE_KERNEL + /* When using -mkernel_profile there is no load to jump over */ + pop = PPC_INST_NOP; + + if (probe_kernel_read(&op, (void *)(ip - 4), 4)) { + pr_err("Fetching instruction at %lx failed.\n", ip - 4); + return -EFAULT; + } + + /* We expect either a mflr r0, or a std r0, LRSAVE(r1) */ + if (op != PPC_INST_MFLR && op != PPC_INST_STD_LR) { + pr_err("Unexpected instruction %08x around bl _mcount\n", op); + return -EINVAL; + } +#else /* * Our original call site looks like: * @@ -170,24 +185,10 @@ __ftrace_make_nop(struct module *mod, } if (op != PPC_INST_LD_TOC) { - unsigned int inst; - - if (probe_kernel_read(&inst, (void *)(ip - 4), 4)) { - pr_err("Fetching instruction at %lx failed.\n", ip - 4); - return -EFAULT; - } - - /* We expect either a mlfr r0, or a std r0, LRSAVE(r1) */ - if (inst != PPC_INST_MFLR && inst != PPC_INST_STD_LR) { - pr_err("Unexpected instructions around bl _mcount\n" - "when enabling dynamic ftrace!\t" - "(%08x,bl,%08x)\n", inst, op); - return -EINVAL; - } - - /* When using -mkernel_profile there is no load to jump over */ - pop = PPC_INST_NOP; + pr_err("Expected %08x found %08x\n", PPC_INST_LD_TOC, op); + return -EINVAL; } +#endif /* CC_USING_MPROFILE_KERNEL */ if (patch_instruction((unsigned int *)ip, pop)) { pr_err("Patching NOP failed.\n"); |