From 92ace9991da08827e809c2d120108a96a281e7fc Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Mon, 11 Dec 2017 11:36:46 -0500 Subject: add infrastructure for tagging functions as error injectable Using BPF we can override kprob'ed functions and return arbitrary values. Obviously this can be a bit unsafe, so make this feature opt-in for functions. Simply tag a function with KPROBE_ERROR_INJECT_SYMBOL in order to give BPF access to that function for error injection purposes. Signed-off-by: Josef Bacik Acked-by: Ingo Molnar Signed-off-by: Alexei Starovoitov --- kernel/module.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'kernel/module.c') diff --git a/kernel/module.c b/kernel/module.c index dea01ac9cb74..bd695bfdc5c4 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3118,7 +3118,11 @@ static int find_module_sections(struct module *mod, struct load_info *info) sizeof(*mod->ftrace_callsites), &mod->num_ftrace_callsites); #endif - +#ifdef CONFIG_BPF_KPROBE_OVERRIDE + mod->kprobe_ei_funcs = section_objs(info, "_kprobe_error_inject_list", + sizeof(*mod->kprobe_ei_funcs), + &mod->num_kprobe_ei_funcs); +#endif mod->extable = section_objs(info, "__ex_table", sizeof(*mod->extable), &mod->num_exentries); -- cgit From b865ea64304ed591b7ab92d74efb12eff5ff4cbb Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Fri, 10 Nov 2017 08:48:25 +0900 Subject: sections: split dereference_function_descriptor() There are two format specifiers to print out a pointer in symbolic format: '%pS/%ps' and '%pF/%pf'. On most architectures, the two mean exactly the same thing, but some architectures (ia64, ppc64, parisc64) use an indirect pointer for C function pointers, where the function pointer points to a function descriptor (which in turn contains the actual pointer to the code). The '%pF/%pf, when used appropriately, automatically does the appropriate function descriptor dereference on such architectures. The "when used appropriately" part is tricky. Basically this is a subtle ABI detail, specific to some platforms, that made it to the API level and people can be unaware of it and miss the whole "we need to dereference the function" business out. [1] proves that point (note that it fixes only '%pF' and '%pS', there might be '%pf' and '%ps' cases as well). It appears that we can handle everything within the affected arches and make '%pS/%ps' smart enough to retire '%pF/%pf'. Function descriptors live in .opd elf section and all affected arches (ia64, ppc64, parisc64) handle it properly for kernel and modules. So we, technically, can decide if the dereference is needed by simply looking at the pointer: if it belongs to .opd section then we need to dereference it. The kernel and modules have their own .opd sections, obviously, that's why we need to split dereference_function_descriptor() and use separate kernel and module dereference arch callbacks. This patch does the first step, it a) adds dereference_kernel_function_descriptor() function. b) adds a weak alias to dereference_module_function_descriptor() function. So, for the time being, we will have: 1) dereference_function_descriptor() A generic function, that simply dereferences the pointer. There is bunch of places that call it: kgdbts, init/main.c, extable, etc. 2) dereference_kernel_function_descriptor() A function to call on kernel symbols that does kernel .opd section address range test. 3) dereference_module_function_descriptor() A function to call on modules' symbols that does modules' .opd section address range test. [1] https://marc.info/?l=linux-kernel&m=150472969730573 Link: http://lkml.kernel.org/r/20171109234830.5067-2-sergey.senozhatsky@gmail.com To: Fenghua Yu To: Benjamin Herrenschmidt To: Paul Mackerras To: Michael Ellerman To: James Bottomley Cc: Andrew Morton Cc: Jessica Yu Cc: Steven Rostedt Cc: linux-ia64@vger.kernel.org Cc: linux-parisc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Sergey Senozhatsky Tested-by: Tony Luck #ia64 Tested-by: Santosh Sivaraj #powerpc Tested-by: Helge Deller #parisc64 Signed-off-by: Petr Mladek --- kernel/module.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'kernel/module.c') diff --git a/kernel/module.c b/kernel/module.c index f0411a271765..65f6561d70e1 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3938,6 +3938,12 @@ static const char *get_ksymbol(struct module *mod, return symname(kallsyms, best); } +void * __weak dereference_module_function_descriptor(struct module *mod, + void *ptr) +{ + return ptr; +} + /* For kallsyms to ask for address resolution. NULL means not found. Careful * not to lock to avoid deadlock on oopses, simply disable preemption. */ const char *module_address_lookup(unsigned long addr, -- cgit From 540adea3809f61115d2a1ea4ed6e627613452ba1 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Sat, 13 Jan 2018 02:55:03 +0900 Subject: error-injection: Separate error-injection from kprobe Since error-injection framework is not limited to be used by kprobes, nor bpf. Other kernel subsystems can use it freely for checking safeness of error-injection, e.g. livepatch, ftrace etc. So this separate error-injection framework from kprobes. Some differences has been made: - "kprobe" word is removed from any APIs/structures. - BPF_ALLOW_ERROR_INJECTION() is renamed to ALLOW_ERROR_INJECTION() since it is not limited for BPF too. - CONFIG_FUNCTION_ERROR_INJECTION is the config item of this feature. It is automatically enabled if the arch supports error injection feature for kprobe or ftrace etc. Signed-off-by: Masami Hiramatsu Reviewed-by: Josef Bacik Signed-off-by: Alexei Starovoitov --- kernel/module.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'kernel/module.c') diff --git a/kernel/module.c b/kernel/module.c index bd695bfdc5c4..601494d4b7ea 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3118,10 +3118,10 @@ static int find_module_sections(struct module *mod, struct load_info *info) sizeof(*mod->ftrace_callsites), &mod->num_ftrace_callsites); #endif -#ifdef CONFIG_BPF_KPROBE_OVERRIDE - mod->kprobe_ei_funcs = section_objs(info, "_kprobe_error_inject_list", - sizeof(*mod->kprobe_ei_funcs), - &mod->num_kprobe_ei_funcs); +#ifdef CONFIG_FUNCTION_ERROR_INJECTION + mod->ei_funcs = section_objs(info, "_error_injection_whitelist", + sizeof(*mod->ei_funcs), + &mod->num_ei_funcs); #endif mod->extable = section_objs(info, "__ex_table", sizeof(*mod->extable), &mod->num_exentries); -- cgit