62 #ifdef LTTNG_CONFIG_PPC64_ELF_ABI_V2 63 /* Substract 4 bytes to get what we originally want */ 64 addr = (unsigned long)(((char *)probe.addr) - 4); 65 #elif defined*(LTTNG_*CONFIG_PPC64_ELF_ABI_V1) << incorrect MACRO to used in gerrit review. this is the correct one. 66 /* 67 * Build a function descriptor from the address of
/lttng-module-2.13.8/src/wrapper/kallsyms.c:72:32: error: invalid use of undefined type 'struct func_desc' | 72 | kallsyms_lookup_name_func_desc.addr = (unsigned long)probe.addr; /lttng-module-2.13.8/src/wrapper/kallsyms.c:73:32: error: invalid use of undefined type 'struct func_desc' | 73 | kallsyms_lookup_name_func_desc.toc = ((struct func_desc *) &sprint_symbol)->toc; you either want to use func_descr_t https://elixir.bootlin.com/linux/v5.15.104/source/arch/powerpc/include/asm/types.h#L30 or struct ppc64_opd_entry https://elixir.bootlin.com/linux/v5.17.15/source/arch/powerpc/include/uapi/asm/elf.h#L293 both of which are discontinued from 5.18 On Mon, Mar 27, 2023 at 5:56 PM Mathieu Desnoyers < mathieu.desnoy...@efficios.com> wrote: > On 2023-03-26 11:00, yashvardhan kukreti wrote: > > > > Hi Mathew, > > > > I have a question about this patch for lttng-modules and the use of > > register_kprobe() to fetch the function ptr. > > The question in this regard is especially from PPC64 ELF_ABI_v1 > > perspective. > > > > The functions on PPC64 are accessed via the Function descriptor > > while what register_kprobes returns is the entry point of the > function. > > Hence using the return pointer tends to interpret the addr as the > > address of the function descriptor and dereferences the ppc_inst as > > the function entry point and crashes > > > > [ 4145.483594] kernel tried to execute exec-protected page > > (7c0802a6fb81ffe0) - exploit attempt? (uid: 0) > > here 7c0802a6 is the mfspr instruction from the code text section of > > the kallsyms_lookup_name() > > > > note for PPC_ELF_ABI_v1 the register_kprobes() searches for the dot > > variant of the symbol and only in case if cannot find the dot > > variant looks for the normal symbol. > > register_kprobe() -> kprobe_addr() -> kprobe_lookup_name() [arch > > variant replaces weak symbol] > > > https://elixir.bootlin.com/linux/v5.10.174/C/ident/kprobe_lookup_name < > https://elixir.bootlin.com/linux/v5.10.174/C/ident/kprobe_lookup_name> > > > > Please let me know if i make sense or that i may have missed > something. > > > > I have looked at the code of 2.12.8 as well and 2.12.3 verstion of > > lttng-modules. > > Please have a look at commits (from stable-2.12 branch of lttng-modules): > > commit 53772db24facd84f1f3ddcf21a1ef5f162608721 > Author: He Zhe <zhe...@windriver.com> > Date: Tue Sep 27 15:59:42 2022 +0800 > > wrapper: powerpc64: fix kernel crash caused by do_get_kallsyms > > commit 8fe888d86ccad4226b05a536efb73d71bb091062 > Author: Michael Jeanson <mjean...@efficios.com> > Date: Thu Nov 24 14:25:33 2022 -0500 > > fix: kallsyms wrapper on ppc64el > > I suspect you'll also need this change currently in review: > > https://review.lttng.org/c/lttng-modules/+/9113 > > Please let us know if especially this last change fixes things on your > side. > > Thanks, > > Mathieu > > > > > > Regards, > > Shashank > > > > -- > Mathieu Desnoyers > EfficiOS Inc. > https://www.efficios.com > >
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