| Message ID | 20170916035347.19705-4-sergey.senozhatsky@gmail.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | printk/ia64/ppc64/parisc64: let's deprecate %pF/%pf printk specifiers | expand |
On 2017/09/16 12:53PM, Sergey Senozhatsky wrote: > We are moving towards separate kernel and module function descriptor > dereference callbacks. This patch enables it for powerpc64. > > For pointers that belong to the kernel > - Added __start_opd and __end_opd pointers, to track the kernel > .opd section address range; > > - Added dereference_kernel_function_descriptor(). Now we > will dereference only function pointers that are within > [__start_opd, __end_opd]; > > For pointers that belong to a module > - Added dereference_module_function_descriptor() to handle module > function descriptor dereference. Now we will dereference only > pointers that are within [module->opd.start, module->opd.end]. Would it be simpler to just use kernel_text_address() and dereference everything else? See commit 83e840c770f2c5 ("powerpc64/elfv1: Only dereference function descriptor for non-text symbols") for a related patch. - Naveen
On (09/16/17 15:13), Naveen N. Rao wrote: [..] > Would it be simpler to just use kernel_text_address() and dereference > everything else? See commit 83e840c770f2c5 ("powerpc64/elfv1: Only > dereference function descriptor for non-text symbols") for a related > patch. I had this idea, see lkml.kernel.org/r/20170908172528.qc2vdtxzqh777k6o@intel.com -ss
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> writes: > On 2017/09/16 12:53PM, Sergey Senozhatsky wrote: >> We are moving towards separate kernel and module function descriptor >> dereference callbacks. This patch enables it for powerpc64. >> >> For pointers that belong to the kernel >> - Added __start_opd and __end_opd pointers, to track the kernel >> .opd section address range; >> >> - Added dereference_kernel_function_descriptor(). Now we >> will dereference only function pointers that are within >> [__start_opd, __end_opd]; >> >> For pointers that belong to a module >> - Added dereference_module_function_descriptor() to handle module >> function descriptor dereference. Now we will dereference only >> pointers that are within [module->opd.start, module->opd.end]. > > Would it be simpler to just use kernel_text_address() and dereference > everything else? See commit 83e840c770f2c5 ("powerpc64/elfv1: Only > dereference function descriptor for non-text symbols") for a related > patch. Yeah that would be a lot simpler and probably work perfectly well. cheers
On (09/19/17 20:22), Michael Ellerman wrote: > > On 2017/09/16 12:53PM, Sergey Senozhatsky wrote: > >> We are moving towards separate kernel and module function descriptor > >> dereference callbacks. This patch enables it for powerpc64. > >> > >> For pointers that belong to the kernel > >> - Added __start_opd and __end_opd pointers, to track the kernel > >> .opd section address range; > >> > >> - Added dereference_kernel_function_descriptor(). Now we > >> will dereference only function pointers that are within > >> [__start_opd, __end_opd]; > >> > >> For pointers that belong to a module > >> - Added dereference_module_function_descriptor() to handle module > >> function descriptor dereference. Now we will dereference only > >> pointers that are within [module->opd.start, module->opd.end]. > > > > Would it be simpler to just use kernel_text_address() and dereference > > everything else? See commit 83e840c770f2c5 ("powerpc64/elfv1: Only > > dereference function descriptor for non-text symbols") for a related > > patch. > > Yeah that would be a lot simpler and probably work perfectly well. unlike ppc_function_entry(), printk() can get called on any symbol, not just function pointers. for example, cat /proc/kallsyms | grep shrinker_rwsem ffffffff81a4b1e0 d shrinker_rwsem or cat /proc/kallsyms | grep vm_total_pages ffffffff81dcd418 B vm_total_pages and so on. -ss
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> writes: > On (09/19/17 20:22), Michael Ellerman wrote: >> > On 2017/09/16 12:53PM, Sergey Senozhatsky wrote: >> >> We are moving towards separate kernel and module function descriptor >> >> dereference callbacks. This patch enables it for powerpc64. >> >> >> >> For pointers that belong to the kernel >> >> - Added __start_opd and __end_opd pointers, to track the kernel >> >> .opd section address range; >> >> >> >> - Added dereference_kernel_function_descriptor(). Now we >> >> will dereference only function pointers that are within >> >> [__start_opd, __end_opd]; >> >> >> >> For pointers that belong to a module >> >> - Added dereference_module_function_descriptor() to handle module >> >> function descriptor dereference. Now we will dereference only >> >> pointers that are within [module->opd.start, module->opd.end]. >> > >> > Would it be simpler to just use kernel_text_address() and dereference >> > everything else? See commit 83e840c770f2c5 ("powerpc64/elfv1: Only >> > dereference function descriptor for non-text symbols") for a related >> > patch. >> >> Yeah that would be a lot simpler and probably work perfectly well. > > unlike ppc_function_entry(), printk() can get called on any symbol, > not just function pointers. > > for example, > > cat /proc/kallsyms | grep shrinker_rwsem > ffffffff81a4b1e0 d shrinker_rwsem Yep, good point. So your patch is probably good then. Maybe someone other than me can find time to test it ;) cheers
On (09/20/17 11:51), Michael Ellerman wrote: [..] > > unlike ppc_function_entry(), printk() can get called on any symbol, > > not just function pointers. > > > > for example, > > > > cat /proc/kallsyms | grep shrinker_rwsem > > ffffffff81a4b1e0 d shrinker_rwsem > > Yep, good point. So your patch is probably good then. Maybe someone > other than me can find time to test it ;) Hi, I'll re-spin the series today/tomorrow. -ss
diff --git a/arch/powerpc/include/asm/module.h b/arch/powerpc/include/asm/module.h index 6c0132c7212f..7e28442827f1 100644 --- a/arch/powerpc/include/asm/module.h +++ b/arch/powerpc/include/asm/module.h @@ -45,6 +45,9 @@ struct mod_arch_specific { unsigned long tramp; #endif + /* For module function descriptor dereference */ + unsigned long start_opd; + unsigned long end_opd; #else /* powerpc64 */ /* Indices of PLT sections within module. */ unsigned int core_plt_section; diff --git a/arch/powerpc/include/asm/sections.h b/arch/powerpc/include/asm/sections.h index 7902d6358854..7cc4db86952b 100644 --- a/arch/powerpc/include/asm/sections.h +++ b/arch/powerpc/include/asm/sections.h @@ -16,6 +16,9 @@ extern char __end_interrupts[]; extern char __prom_init_toc_start[]; extern char __prom_init_toc_end[]; +extern char __start_opd[]; +extern char __end_opd[]; + static inline int in_kernel_text(unsigned long addr) { if (addr >= (unsigned long)_stext && addr < (unsigned long)__init_end) @@ -66,6 +69,8 @@ static inline int overlaps_kvm_tmp(unsigned long start, unsigned long end) #ifdef PPC64_ELF_ABI_v1 #undef dereference_function_descriptor +#undef dereference_kernel_function_descriptor + static inline void *dereference_function_descriptor(void *ptr) { struct ppc64_opd_entry *desc = ptr; @@ -75,6 +80,14 @@ static inline void *dereference_function_descriptor(void *ptr) ptr = p; return ptr; } + +static inline void *dereference_kernel_function_descriptor(void *ptr) +{ + if (ptr < (void *)__start_opd || (void *)__end_opd < ptr) + return ptr; + + return dereference_function_descriptor(ptr); +} #endif /* PPC64_ELF_ABI_v1 */ #endif diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c index 0b0f89685b67..52aa5d668364 100644 --- a/arch/powerpc/kernel/module_64.c +++ b/arch/powerpc/kernel/module_64.c @@ -344,6 +344,11 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr, else if (strcmp(secstrings+sechdrs[i].sh_name,"__versions")==0) dedotify_versions((void *)hdr + sechdrs[i].sh_offset, sechdrs[i].sh_size); + else if (strcmp(secstrings + sechdrs[i].sh_name, ".opd")==0) { + me->arch.start_opd = sechdrs[i].sh_offset; + me->arch.end_opd = me->arch.start_opd + + sechdrs[i].sh_size; + } /* We don't handle .init for the moment: rename to _init */ while ((p = strstr(secstrings + sechdrs[i].sh_name, ".init"))) @@ -712,6 +717,17 @@ int apply_relocate_add(Elf64_Shdr *sechdrs, return 0; } +#ifdef PPC64_ELF_ABI_v1 +unsigned long dereference_module_function_descriptor(struct module *mod, + unsigned long addr) +{ + if (addr < mod->arch.start_opd || mod->arch.end_opd < addr) + return addr; + + return dereference_function_descriptor(addr); +} +#endif /* PPC64_ELF_ABI_v1 */ + #ifdef CONFIG_DYNAMIC_FTRACE #ifdef CC_USING_MPROFILE_KERNEL diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index 882628fa6987..70e10251e083 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -277,7 +277,9 @@ SECTIONS } .opd : AT(ADDR(.opd) - LOAD_OFFSET) { + __start_opd = .; *(.opd) + __end_opd = .; } . = ALIGN(256);
We are moving towards separate kernel and module function descriptor dereference callbacks. This patch enables it for powerpc64. For pointers that belong to the kernel - Added __start_opd and __end_opd pointers, to track the kernel .opd section address range; - Added dereference_kernel_function_descriptor(). Now we will dereference only function pointers that are within [__start_opd, __end_opd]; For pointers that belong to a module - Added dereference_module_function_descriptor() to handle module function descriptor dereference. Now we will dereference only pointers that are within [module->opd.start, module->opd.end]. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> --- arch/powerpc/include/asm/module.h | 3 +++ arch/powerpc/include/asm/sections.h | 13 +++++++++++++ arch/powerpc/kernel/module_64.c | 16 ++++++++++++++++ arch/powerpc/kernel/vmlinux.lds.S | 2 ++ 4 files changed, 34 insertions(+)