Architecture must select HAVE_SECCOMP_FILTER_JIT and implement seccomp_jit_compile() and seccomp_jit_free() if they intend to support jitted seccomp filters.
struct seccomp_filter has been moved to <linux/seccomp.h> to make its content available to the jit compilation code. In a way similar to the net BPF, the jit compilation code is expected to updates struct seccomp_filter.bpf_func pointer to the generated code. Signed-off-by: Nicolas Schichan <nschic...@freebox.fr> --- arch/Kconfig | 14 ++++++++++++++ include/linux/seccomp.h | 41 +++++++++++++++++++++++++++++++++++++++++ kernel/seccomp.c | 34 +++++----------------------------- 3 files changed, 60 insertions(+), 29 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 5a1779c..1284367 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -339,6 +339,10 @@ config HAVE_ARCH_SECCOMP_FILTER - secure_computing return value is checked and a return value of -1 results in the system call being skipped immediately. +# Used by archs to tell that they support SECCOMP_FILTER_JIT +config HAVE_SECCOMP_FILTER_JIT + bool + config SECCOMP_FILTER def_bool y depends on HAVE_ARCH_SECCOMP_FILTER && SECCOMP && NET @@ -349,6 +353,16 @@ config SECCOMP_FILTER See Documentation/prctl/seccomp_filter.txt for details. +config SECCOMP_FILTER_JIT + bool "enable Seccomp filter Just In Time compiler" + depends on HAVE_SECCOMP_FILTER_JIT && BPF_JIT && SECCOMP_FILTER + help + Seccomp syscall filtering capabilities are normally handled + by an interpreter. This option allows kernel to generate a native + code when filter is loaded in memory. This should speedup + syscall filtering. Note : Admin should enable this feature + changing /proc/sys/net/core/bpf_jit_enable + config HAVE_CONTEXT_TRACKING bool help diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index 6f19cfd..a216ab7 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -6,6 +6,7 @@ #ifdef CONFIG_SECCOMP #include <linux/thread_info.h> +#include <linux/filter.h> #include <asm/seccomp.h> struct seccomp_filter; @@ -47,6 +48,46 @@ static inline int seccomp_mode(struct seccomp *s) return s->mode; } +/** + * struct seccomp_filter - container for seccomp BPF programs + * + * @usage: reference count to manage the object lifetime. + * get/put helpers should be used when accessing an instance + * outside of a lifetime-guarded section. In general, this + * is only needed for handling filters shared across tasks. + * @prev: points to a previously installed, or inherited, filter + * @len: the number of instructions in the program + * @bpc_func: points to either sk_run_filter or the code generated + * by the BPF JIT. + * @insns: the BPF program instructions to evaluate + * + * seccomp_filter objects are organized in a tree linked via the @prev + * pointer. For any task, it appears to be a singly-linked list starting + * with current->seccomp.filter, the most recently attached or inherited filter. + * However, multiple filters may share a @prev node, by way of fork(), which + * results in a unidirectional tree existing in memory. This is similar to + * how namespaces work. + * + * seccomp_filter objects should never be modified after being attached + * to a task_struct (other than @usage). + */ +struct seccomp_filter { + atomic_t usage; + struct seccomp_filter *prev; + unsigned short len; /* Instruction count */ + unsigned int (*bpf_func)(const struct sk_buff *skb, + const struct sock_filter *filter); + struct sock_filter insns[]; +}; + +#ifdef CONFIG_SECCOMP_FILTER_JIT +extern void seccomp_jit_compile(struct seccomp_filter *fp); +extern void seccomp_jit_free(struct seccomp_filter *fp); +#else +static inline void seccomp_jit_compile(struct seccomp_filter *fp) { } +static inline void seccomp_jit_free(struct seccomp_filter *fp) { } +#endif + #else /* CONFIG_SECCOMP */ #include <linux/errno.h> diff --git a/kernel/seccomp.c b/kernel/seccomp.c index b7a1004..a1aadaa 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -30,34 +30,6 @@ #include <linux/tracehook.h> #include <linux/uaccess.h> -/** - * struct seccomp_filter - container for seccomp BPF programs - * - * @usage: reference count to manage the object lifetime. - * get/put helpers should be used when accessing an instance - * outside of a lifetime-guarded section. In general, this - * is only needed for handling filters shared across tasks. - * @prev: points to a previously installed, or inherited, filter - * @len: the number of instructions in the program - * @insns: the BPF program instructions to evaluate - * - * seccomp_filter objects are organized in a tree linked via the @prev - * pointer. For any task, it appears to be a singly-linked list starting - * with current->seccomp.filter, the most recently attached or inherited filter. - * However, multiple filters may share a @prev node, by way of fork(), which - * results in a unidirectional tree existing in memory. This is similar to - * how namespaces work. - * - * seccomp_filter objects should never be modified after being attached - * to a task_struct (other than @usage). - */ -struct seccomp_filter { - atomic_t usage; - struct seccomp_filter *prev; - unsigned short len; /* Instruction count */ - struct sock_filter insns[]; -}; - /* Limit any path through the tree to 256KB worth of instructions. */ #define MAX_INSNS_PER_PATH ((1 << 18) / sizeof(struct sock_filter)) @@ -213,7 +185,7 @@ static u32 seccomp_run_filters(int syscall) * value always takes priority (ignoring the DATA). */ for (f = current->seccomp.filter; f; f = f->prev) { - u32 cur_ret = sk_run_filter(NULL, f->insns); + u32 cur_ret = f->bpf_func(NULL, f->insns); if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION)) ret = cur_ret; } @@ -275,6 +247,9 @@ static long seccomp_attach_filter(struct sock_fprog *fprog) if (ret) goto fail; + filter->bpf_func = sk_run_filter; + seccomp_jit_compile(filter); + /* * If there is an existing filter, make it the prev and don't drop its * task reference. @@ -332,6 +307,7 @@ void put_seccomp_filter(struct task_struct *tsk) while (orig && atomic_dec_and_test(&orig->usage)) { struct seccomp_filter *freeme = orig; orig = orig->prev; + seccomp_jit_free(freeme); kfree(freeme); } } -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/