| Message ID | da4200e511f4863b153b0721f3913a75aa3bf80d.1561634177.git.naveen.n.rao@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | powerpc/ftrace: Patch out -mprofile-kernel instructions | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | Successfully applied on branch next (c7d64b560ce80d8c44f082eee8352f0778a73195) |
| snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
| snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
| snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
| snowpatch_ozlabs/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 64 lines checked |
On Thu, 27 Jun 2019 16:53:55 +0530 "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote: > With KPROBES_ON_FTRACE, kprobe is allowed to be inserted on instructions > that branch to _mcount (referred to as ftrace location). With > -mprofile-kernel, we now include the preceding 'mflr r0' as being part > of the ftrace location. > > However, by default, probing on an instruction that is not actually the > branch to _mcount() is prohibited, as that is considered to not be at an > instruction boundary. This is not the case on powerpc, so allow the same > by overriding arch_check_ftrace_location() > > In addition, we update kprobe_ftrace_handler() to detect this scenarios > and to pass the proper nip to the pre and post probe handlers. > > Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Looks good to me. Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org> Thank you! > --- > arch/powerpc/kernel/kprobes-ftrace.c | 32 +++++++++++++++++++++++++++- > 1 file changed, 31 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/kprobes-ftrace.c b/arch/powerpc/kernel/kprobes-ftrace.c > index 972cb28174b2..23c840748183 100644 > --- a/arch/powerpc/kernel/kprobes-ftrace.c > +++ b/arch/powerpc/kernel/kprobes-ftrace.c > @@ -12,15 +12,35 @@ > #include <linux/preempt.h> > #include <linux/ftrace.h> > > +/* > + * With -mprofile-kernel, we patch two instructions -- the branch to _mcount > + * as well as the preceding 'mflr r0'. Both these instructions are claimed > + * by ftrace and we should allow probing on either instruction. > + */ > +int arch_check_ftrace_location(struct kprobe *p) > +{ > + if (ftrace_location((unsigned long)p->addr)) > + p->flags |= KPROBE_FLAG_FTRACE; > + return 0; > +} > + > /* Ftrace callback handler for kprobes */ > void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, > struct ftrace_ops *ops, struct pt_regs *regs) > { > struct kprobe *p; > + int mflr_kprobe = 0; > struct kprobe_ctlblk *kcb; > > p = get_kprobe((kprobe_opcode_t *)nip); > - if (unlikely(!p) || kprobe_disabled(p)) > + if (!p) { > + p = get_kprobe((kprobe_opcode_t *)(nip - MCOUNT_INSN_SIZE)); > + if (unlikely(!p)) > + return; > + mflr_kprobe = 1; > + } > + > + if (kprobe_disabled(p)) > return; > > kcb = get_kprobe_ctlblk(); > @@ -33,6 +53,9 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, > */ > regs->nip -= MCOUNT_INSN_SIZE; > > + if (mflr_kprobe) > + regs->nip -= MCOUNT_INSN_SIZE; > + > __this_cpu_write(current_kprobe, p); > kcb->kprobe_status = KPROBE_HIT_ACTIVE; > if (!p->pre_handler || !p->pre_handler(p, regs)) { > @@ -45,6 +68,8 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, > kcb->kprobe_status = KPROBE_HIT_SSDONE; > p->post_handler(p, regs, 0); > } > + if (mflr_kprobe) > + regs->nip += MCOUNT_INSN_SIZE; > } > /* > * If pre_handler returns !0, it changes regs->nip. We have to > @@ -57,6 +82,11 @@ NOKPROBE_SYMBOL(kprobe_ftrace_handler); > > int arch_prepare_kprobe_ftrace(struct kprobe *p) > { > + if ((unsigned long)p->addr & 0x03) { > + pr_err("Attempt to register kprobe at an unaligned address\n"); > + return -EILSEQ; > + } > + > p->ainsn.insn = NULL; > p->ainsn.boostable = -1; > return 0; > -- > 2.22.0 >
diff --git a/arch/powerpc/kernel/kprobes-ftrace.c b/arch/powerpc/kernel/kprobes-ftrace.c index 972cb28174b2..23c840748183 100644 --- a/arch/powerpc/kernel/kprobes-ftrace.c +++ b/arch/powerpc/kernel/kprobes-ftrace.c @@ -12,15 +12,35 @@ #include <linux/preempt.h> #include <linux/ftrace.h> +/* + * With -mprofile-kernel, we patch two instructions -- the branch to _mcount + * as well as the preceding 'mflr r0'. Both these instructions are claimed + * by ftrace and we should allow probing on either instruction. + */ +int arch_check_ftrace_location(struct kprobe *p) +{ + if (ftrace_location((unsigned long)p->addr)) + p->flags |= KPROBE_FLAG_FTRACE; + return 0; +} + /* Ftrace callback handler for kprobes */ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, struct ftrace_ops *ops, struct pt_regs *regs) { struct kprobe *p; + int mflr_kprobe = 0; struct kprobe_ctlblk *kcb; p = get_kprobe((kprobe_opcode_t *)nip); - if (unlikely(!p) || kprobe_disabled(p)) + if (!p) { + p = get_kprobe((kprobe_opcode_t *)(nip - MCOUNT_INSN_SIZE)); + if (unlikely(!p)) + return; + mflr_kprobe = 1; + } + + if (kprobe_disabled(p)) return; kcb = get_kprobe_ctlblk(); @@ -33,6 +53,9 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, */ regs->nip -= MCOUNT_INSN_SIZE; + if (mflr_kprobe) + regs->nip -= MCOUNT_INSN_SIZE; + __this_cpu_write(current_kprobe, p); kcb->kprobe_status = KPROBE_HIT_ACTIVE; if (!p->pre_handler || !p->pre_handler(p, regs)) { @@ -45,6 +68,8 @@ void kprobe_ftrace_handler(unsigned long nip, unsigned long parent_nip, kcb->kprobe_status = KPROBE_HIT_SSDONE; p->post_handler(p, regs, 0); } + if (mflr_kprobe) + regs->nip += MCOUNT_INSN_SIZE; } /* * If pre_handler returns !0, it changes regs->nip. We have to @@ -57,6 +82,11 @@ NOKPROBE_SYMBOL(kprobe_ftrace_handler); int arch_prepare_kprobe_ftrace(struct kprobe *p) { + if ((unsigned long)p->addr & 0x03) { + pr_err("Attempt to register kprobe at an unaligned address\n"); + return -EILSEQ; + } + p->ainsn.insn = NULL; p->ainsn.boostable = -1; return 0;
With KPROBES_ON_FTRACE, kprobe is allowed to be inserted on instructions that branch to _mcount (referred to as ftrace location). With -mprofile-kernel, we now include the preceding 'mflr r0' as being part of the ftrace location. However, by default, probing on an instruction that is not actually the branch to _mcount() is prohibited, as that is considered to not be at an instruction boundary. This is not the case on powerpc, so allow the same by overriding arch_check_ftrace_location() In addition, we update kprobe_ftrace_handler() to detect this scenarios and to pass the proper nip to the pre and post probe handlers. Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> --- arch/powerpc/kernel/kprobes-ftrace.c | 32 +++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-)