* [PATCH v1 0/3] Introduce the latent_entropy gcc plugin
@ 2016-05-23 22:14 Emese Revfy
2016-05-23 22:15 ` [PATCH v1 1/3] Add " Emese Revfy
` (2 more replies)
0 siblings, 3 replies; 14+ messages in thread
From: Emese Revfy @ 2016-05-23 22:14 UTC (permalink / raw)
To: kernel-hardening
Cc: pageexec, spender, mmarek, keescook, linux-kernel,
yamada.masahiro, linux-kbuild, tytso, akpm, linux-mm, axboe,
viro, paulmck, mingo, tglx, bart.vanassche, davem
I would like to introduce the latent_entropy gcc plugin. This plugin mitigates
the problem of the kernel having too little entropy during and after boot
for generating crypto keys.
This plugin mixes random values into the latent_entropy global variable
in functions marked by the __latent_entropy attribute.
The value of this global variable is added to the kernel entropy pool
to increase the entropy.
It is a CII project supported by the Linux Foundation.
The latent_entropy plugin was ported from grsecurity/PaX originally written by
the PaX Team. You can find more about the plugin here:
https://grsecurity.net/pipermail/grsecurity/2012-July/001093.html
The plugin supports all gcc version from 4.5 to 6.0.
I do some changes above the PaX version. The important one is mixing
the stack pointer into the global variable too.
You can find more about the changes here:
https://github.com/ephox-gcc-plugins/latent_entropy
This patch set is based on the "Introduce GCC plugin infrastructure" patch set (v9).
Emese Revfy (3):
Add the latent_entropy gcc plugin
Mark functions with the latent_entropy attribute
Add the extra_latent_entropy kernel parameter
---
Documentation/kernel-parameters.txt | 5 +
arch/Kconfig | 22 ++
arch/powerpc/kernel/Makefile | 8 +-
block/blk-softirq.c | 2 +-
drivers/char/random.c | 6 +-
fs/namespace.c | 2 +-
include/linux/compiler-gcc.h | 5 +
include/linux/compiler.h | 4 +
include/linux/fdtable.h | 2 +-
include/linux/genhd.h | 2 +-
include/linux/init.h | 10 +-
include/linux/random.h | 12 +-
init/main.c | 1 +
kernel/fork.c | 5 +-
kernel/rcu/tiny.c | 2 +-
kernel/rcu/tree.c | 2 +-
kernel/sched/fair.c | 2 +-
kernel/softirq.c | 4 +-
kernel/time/timer.c | 2 +-
lib/irq_poll.c | 2 +-
lib/random32.c | 2 +-
mm/page_alloc.c | 28 ++
net/core/dev.c | 4 +-
scripts/Makefile.gcc-plugins | 10 +-
scripts/gcc-plugins/Makefile | 1 +
scripts/gcc-plugins/latent_entropy_plugin.c | 446 ++++++++++++++++++++++++++++
26 files changed, 562 insertions(+), 29 deletions(-)
^ permalink raw reply [flat|nested] 14+ messages in thread* [PATCH v1 1/3] Add the latent_entropy gcc plugin 2016-05-23 22:14 [PATCH v1 0/3] Introduce the latent_entropy gcc plugin Emese Revfy @ 2016-05-23 22:15 ` Emese Revfy 2016-05-24 17:32 ` Kees Cook 2016-05-23 22:16 ` [PATCH v1 2/3] Mark functions with the latent_entropy attribute Emese Revfy 2016-05-23 22:17 ` [PATCH v1 3/3] Add the extra_latent_entropy kernel parameter Emese Revfy 2 siblings, 1 reply; 14+ messages in thread From: Emese Revfy @ 2016-05-23 22:15 UTC (permalink / raw) To: kernel-hardening Cc: pageexec, spender, mmarek, keescook, linux-kernel, yamada.masahiro, linux-kbuild, tytso, akpm, linux-mm, axboe, viro, paulmck, mingo, tglx, bart.vanassche, davem This plugin mitigates the problem of the kernel having too little entropy during and after boot for generating crypto keys. It creates a local variable in every marked function. The value of this variable is modified by randomly chosen operations (add, xor and rol) and random values (gcc generates them at compile time and the stack pointer at runtime). It depends on the control flow (e.g., loops, conditions). Before the function returns the plugin writes this local variable into the latent_entropy global variable. The value of this global variable is added to the kernel entropy pool in do_one_initcall() and _do_fork(). Based on work created by the PaX Team. Signed-off-by: Emese Revfy <re.emese@gmail.com> --- arch/Kconfig | 17 ++ arch/powerpc/kernel/Makefile | 8 +- include/linux/random.h | 8 + init/main.c | 1 + kernel/fork.c | 1 + mm/page_alloc.c | 5 + scripts/Makefile.gcc-plugins | 10 +- scripts/gcc-plugins/Makefile | 1 + scripts/gcc-plugins/latent_entropy_plugin.c | 446 ++++++++++++++++++++++++++++ 9 files changed, 491 insertions(+), 6 deletions(-) create mode 100644 scripts/gcc-plugins/latent_entropy_plugin.c diff --git a/arch/Kconfig b/arch/Kconfig index 5feadad..74489df 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -393,6 +393,23 @@ config GCC_PLUGIN_SANCOV gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" by Dmitry Vyukov <dvyukov@google.com>. +config GCC_PLUGIN_LATENT_ENTROPY + bool "latent entropy" + depends on GCC_PLUGINS + help + By saying Y here the kernel will instrument some kernel code to + extract some entropy from both original and artificially created + program state. This will help especially embedded systems where + there is little 'natural' source of entropy normally. The cost + is some slowdown of the boot process and fork and irq processing. + + Note that entropy extracted this way is not known to be cryptographically + secure! + + This plugin was ported from grsecurity/PaX. More information at: + * https://grsecurity.net/ + * https://pax.grsecurity.net/ + config HAVE_CC_STACKPROTECTOR bool help diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile index 2da380f..6c7e448 100644 --- a/arch/powerpc/kernel/Makefile +++ b/arch/powerpc/kernel/Makefile @@ -16,10 +16,10 @@ endif ifdef CONFIG_FUNCTION_TRACER # Do not trace early boot code -CFLAGS_REMOVE_cputable.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) -CFLAGS_REMOVE_prom_init.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) -CFLAGS_REMOVE_btext.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) -CFLAGS_REMOVE_prom.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) +CFLAGS_REMOVE_cputable.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) $(DISABLE_LATENT_ENTROPY_PLUGIN) +CFLAGS_REMOVE_prom_init.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) $(DISABLE_LATENT_ENTROPY_PLUGIN) +CFLAGS_REMOVE_btext.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) $(DISABLE_LATENT_ENTROPY_PLUGIN) +CFLAGS_REMOVE_prom.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) $(DISABLE_LATENT_ENTROPY_PLUGIN) # do not trace tracer code CFLAGS_REMOVE_ftrace.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) # timers used by tracing diff --git a/include/linux/random.h b/include/linux/random.h index e47e533..379f4bc 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -18,6 +18,14 @@ struct random_ready_callback { }; extern void add_device_randomness(const void *, unsigned int); + +static inline void add_latent_entropy(void) +{ +#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY + add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); +#endif +} + extern void add_input_randomness(unsigned int type, unsigned int code, unsigned int value); extern void add_interrupt_randomness(int irq, int irq_flags); diff --git a/init/main.c b/init/main.c index 4c17fda..07e4174 100644 --- a/init/main.c +++ b/init/main.c @@ -781,6 +781,7 @@ int __init_or_module do_one_initcall(initcall_t fn) } WARN(msgbuf[0], "initcall %pF returned with %s\n", fn, msgbuf); + add_latent_entropy(); return ret; } diff --git a/kernel/fork.c b/kernel/fork.c index cdf520f..d07d5a6 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1766,6 +1766,7 @@ long _do_fork(unsigned long clone_flags, p = copy_process(clone_flags, stack_start, stack_size, child_tidptr, NULL, trace, tls, NUMA_NO_NODE); + add_latent_entropy(); /* * Do this prior waking up the new thread - the thread pointer * might get invalid after that point, if the thread exits quickly. diff --git a/mm/page_alloc.c b/mm/page_alloc.c index f8f3bfc..d10324e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1234,6 +1234,11 @@ static void __free_pages_ok(struct page *page, unsigned int order) local_irq_restore(flags); } +#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY +volatile u64 latent_entropy; +EXPORT_SYMBOL(latent_entropy); +#endif + static void __init __free_pages_boot_core(struct page *page, unsigned int order) { unsigned int nr_pages = 1 << order; diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins index ed37e9b..1540620 100644 --- a/scripts/Makefile.gcc-plugins +++ b/scripts/Makefile.gcc-plugins @@ -6,6 +6,12 @@ ifdef CONFIG_GCC_PLUGINS gcc-plugin-$(CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) += cyc_complexity_plugin.so + gcc-plugin-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) += latent_entropy_plugin.so + gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_LATENT_ENTROPY) += -DLATENT_ENTROPY_PLUGIN + ifdef CONFIG_PAX_LATENT_ENTROPY + DISABLE_LATENT_ENTROPY_PLUGIN += -fplugin-arg-latent_entropy_plugin-disable + endif + ifdef CONFIG_GCC_PLUGIN_SANCOV ifeq ($(CFLAGS_KCOV),) # It is needed because of the gcc-plugin.sh and gcc version checks. @@ -19,9 +25,9 @@ ifdef CONFIG_GCC_PLUGINS endif endif - GCC_PLUGINS_CFLAGS := $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) + GCC_PLUGINS_CFLAGS := $(strip $(addprefix -fplugin=$(objtree)/scripts/gcc-plugins/, $(gcc-plugin-y)) $(gcc-plugin-cflags-y)) - export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN SANCOV_PLUGIN + export PLUGINCC GCC_PLUGINS_CFLAGS GCC_PLUGIN SANCOV_PLUGIN DISABLE_LATENT_ENTROPY_PLUGIN ifeq ($(PLUGINCC),) ifneq ($(GCC_PLUGINS_CFLAGS),) diff --git a/scripts/gcc-plugins/Makefile b/scripts/gcc-plugins/Makefile index 88c8ec4..a3f8ca4a 100644 --- a/scripts/gcc-plugins/Makefile +++ b/scripts/gcc-plugins/Makefile @@ -23,5 +23,6 @@ always := $($(HOSTLIBS)-y) cyc_complexity_plugin-objs := cyc_complexity_plugin.o sancov_plugin-objs := sancov_plugin.o +latent_entropy_plugin-objs := latent_entropy_plugin.o clean-files += *.so diff --git a/scripts/gcc-plugins/latent_entropy_plugin.c b/scripts/gcc-plugins/latent_entropy_plugin.c new file mode 100644 index 0000000..7295c39 --- /dev/null +++ b/scripts/gcc-plugins/latent_entropy_plugin.c @@ -0,0 +1,446 @@ +/* + * Copyright 2012-2016 by the PaX Team <pageexec@freemail.hu> + * Copyright 2016 by Emese Revfy <re.emese@gmail.com> + * Licensed under the GPL v2 + * + * Note: the choice of the license means that the compilation process is + * NOT 'eligible' as defined by gcc's library exception to the GPL v3, + * but for the kernel it doesn't matter since it doesn't link against + * any of the gcc libraries + * + * gcc plugin to help generate a little bit of entropy from program state, + * used throughout the uptime of the kernel + * + * TODO: + * - add ipa pass to identify not explicitly marked candidate functions + * - mix in more program state (function arguments/return values, loop variables, etc) + * - more instrumentation control via attribute parameters + * + * BUGS: + * - none known + */ + +#include "gcc-common.h" + +int plugin_is_GPL_compatible; + +static bool enabled = true; + +static GTY(()) tree latent_entropy_decl; + +static struct plugin_info latent_entropy_plugin_info = { + .version = "201605222100", + .help = "disable\tturn off latent entropy instrumentation\n", +}; + +static unsigned HOST_WIDE_INT seed; +static unsigned HOST_WIDE_INT get_random_const(void) +{ + unsigned int i; + unsigned HOST_WIDE_INT ret = 0; + + for (i = 0; i < 8 * sizeof ret; i++) { + ret = (ret << 1) | (seed & 1); + seed >>= 1; + if (ret & 1) + seed ^= 0xD800000000000000ULL; + } + + return ret; +} + +static tree handle_latent_entropy_attribute(tree *node, tree name, tree args __unused, int flags __unused, bool *no_add_attrs) +{ + tree type; + unsigned long long mask; +#if BUILDING_GCC_VERSION <= 4007 + VEC(constructor_elt, gc) *vals; +#else + vec<constructor_elt, va_gc> *vals; +#endif + + switch (TREE_CODE(*node)) { + default: + *no_add_attrs = true; + error("%qE attribute only applies to functions and variables", name); + break; + + case VAR_DECL: + if (DECL_INITIAL(*node)) { + *no_add_attrs = true; + error("variable %qD with %qE attribute must not be initialized", *node, name); + break; + } + + if (!TREE_STATIC(*node)) { + *no_add_attrs = true; + error("variable %qD with %qE attribute must not be local", *node, name); + break; + } + + type = TREE_TYPE(*node); + switch (TREE_CODE(type)) { + default: + *no_add_attrs = true; + error("variable %qD with %qE attribute must be an integer or a fixed length integer array type" + "or a fixed sized structure with integer fields", *node, name); + break; + + case RECORD_TYPE: { + tree field; + unsigned int nelt = 0; + + for (field = TYPE_FIELDS(type); field; nelt++, field = TREE_CHAIN(field)) { + tree fieldtype; + + fieldtype = TREE_TYPE(field); + if (TREE_CODE(fieldtype) == INTEGER_TYPE) + continue; + + *no_add_attrs = true; + error("structure variable %qD with %qE attribute has a non-integer field %qE", *node, name, field); + break; + } + + if (field) + break; + +#if BUILDING_GCC_VERSION <= 4007 + vals = VEC_alloc(constructor_elt, gc, nelt); +#else + vec_alloc(vals, nelt); +#endif + + for (field = TYPE_FIELDS(type); field; field = TREE_CHAIN(field)) { + tree fieldtype; + + fieldtype = TREE_TYPE(field); + mask = 1ULL << (TREE_INT_CST_LOW(TYPE_SIZE(fieldtype)) - 1); + mask = 2 * (mask - 1) + 1; + + if (TYPE_UNSIGNED(fieldtype)) + CONSTRUCTOR_APPEND_ELT(vals, field, build_int_cstu(fieldtype, mask & get_random_const())); + else + CONSTRUCTOR_APPEND_ELT(vals, field, build_int_cst(fieldtype, mask & get_random_const())); + } + + DECL_INITIAL(*node) = build_constructor(type, vals); + break; + } + + case INTEGER_TYPE: + mask = 1ULL << (TREE_INT_CST_LOW(TYPE_SIZE(type)) - 1); + mask = 2 * (mask - 1) + 1; + + if (TYPE_UNSIGNED(type)) + DECL_INITIAL(*node) = build_int_cstu(type, mask & get_random_const()); + else + DECL_INITIAL(*node) = build_int_cst(type, mask & get_random_const()); + break; + + case ARRAY_TYPE: { + tree elt_type, array_size, elt_size; + unsigned int i, nelt; + + elt_type = TREE_TYPE(type); + elt_size = TYPE_SIZE_UNIT(TREE_TYPE(type)); + array_size = TYPE_SIZE_UNIT(type); + + if (TREE_CODE(elt_type) != INTEGER_TYPE || !array_size || TREE_CODE(array_size) != INTEGER_CST) { + *no_add_attrs = true; + error("array variable %qD with %qE attribute must be a fixed length integer array type", *node, name); + break; + } + + nelt = TREE_INT_CST_LOW(array_size) / TREE_INT_CST_LOW(elt_size); +#if BUILDING_GCC_VERSION <= 4007 + vals = VEC_alloc(constructor_elt, gc, nelt); +#else + vec_alloc(vals, nelt); +#endif + + mask = 1ULL << (TREE_INT_CST_LOW(TYPE_SIZE(elt_type)) - 1); + mask = 2 * (mask - 1) + 1; + + for (i = 0; i < nelt; i++) + if (TYPE_UNSIGNED(elt_type)) + CONSTRUCTOR_APPEND_ELT(vals, size_int(i), build_int_cstu(elt_type, mask & get_random_const())); + else + CONSTRUCTOR_APPEND_ELT(vals, size_int(i), build_int_cst(elt_type, mask & get_random_const())); + + DECL_INITIAL(*node) = build_constructor(type, vals); + break; + } + } + break; + + case FUNCTION_DECL: + break; + } + + return NULL_TREE; +} + +static struct attribute_spec latent_entropy_attr = { + .name = "latent_entropy", + .min_length = 0, + .max_length = 0, + .decl_required = true, + .type_required = false, + .function_type_required = false, + .handler = handle_latent_entropy_attribute, +#if BUILDING_GCC_VERSION >= 4007 + .affects_type_identity = false +#endif +}; + +static void register_attributes(void *event_data __unused, void *data __unused) +{ + register_attribute(&latent_entropy_attr); +} + +static bool latent_entropy_gate(void) +{ + /* don't bother with noreturn functions for now */ + if (TREE_THIS_VOLATILE(current_function_decl)) + return false; + + /* gcc-4.5 doesn't discover some trivial noreturn functions */ + if (EDGE_COUNT(EXIT_BLOCK_PTR_FOR_FN(cfun)->preds) == 0) + return false; + + return lookup_attribute("latent_entropy", DECL_ATTRIBUTES(current_function_decl)) != NULL_TREE; +} + +static tree create_a_tmp_var(tree type, const char *name) +{ + tree var; + + var = create_tmp_var(type, name); + add_referenced_var(var); + mark_sym_for_renaming(var); + return var; +} + +static enum tree_code get_op(tree *rhs) +{ + static enum tree_code op; + unsigned HOST_WIDE_INT random_const; + + random_const = get_random_const(); + + switch (op) { + case BIT_XOR_EXPR: + op = PLUS_EXPR; + break; + + case PLUS_EXPR: + if (rhs) { + op = LROTATE_EXPR; + random_const &= HOST_BITS_PER_WIDE_INT - 1; + break; + } + + case LROTATE_EXPR: + default: + op = BIT_XOR_EXPR; + break; + } + if (rhs) + *rhs = build_int_cstu(unsigned_intDI_type_node, random_const); + return op; +} + +static void perturb_local_entropy(basic_block bb, tree local_entropy) +{ + gimple_stmt_iterator gsi; + gimple assign; + tree rhs; + enum tree_code subcode; + + subcode = get_op(&rhs); + assign = gimple_build_assign_with_ops(subcode, local_entropy, local_entropy, rhs); + gsi = gsi_after_labels(bb); + gsi_insert_before(&gsi, assign, GSI_NEW_STMT); + update_stmt(assign); +} + +static void perturb_latent_entropy(basic_block bb, tree rhs) +{ + gimple_stmt_iterator gsi; + gimple assign; + tree temp; + enum tree_code subcode; + + /* create temporary copy of latent_entropy */ + temp = create_a_tmp_var(unsigned_intDI_type_node, "temp_latent_entropy"); + + gsi = gsi_last_bb(bb); + + /* 3. ...write latent_entropy */ + assign = gimple_build_assign(latent_entropy_decl, temp); + gsi_insert_before(&gsi, assign, GSI_NEW_STMT); + update_stmt(assign); + + /* 2. ...modify... */ + subcode = get_op(NULL); + assign = gimple_build_assign_with_ops(subcode, temp, temp, rhs); + gsi_insert_before(&gsi, assign, GSI_NEW_STMT); + update_stmt(assign); + + /* 1. read... */ + add_referenced_var(latent_entropy_decl); + mark_sym_for_renaming(latent_entropy_decl); + assign = gimple_build_assign(temp, latent_entropy_decl); + gsi_insert_before(&gsi, assign, GSI_NEW_STMT); + update_stmt(assign); +} + +static void mix_in_sp(basic_block bb, tree local_entropy) +{ + gimple assign, call; + tree frame_addr, rand_const; + gimple_stmt_iterator gsi = gsi_after_labels(bb); + + frame_addr = create_a_tmp_var(ptr_type_node, "local_entropy_frame_addr"); + + call = gimple_build_call(builtin_decl_implicit(BUILT_IN_FRAME_ADDRESS), 1, integer_zero_node); + gimple_call_set_lhs(call, frame_addr); + gsi_insert_before(&gsi, call, GSI_NEW_STMT); + update_stmt(call); + + assign = gimple_build_assign(local_entropy, fold_convert(unsigned_intDI_type_node, frame_addr)); + gsi_insert_after(&gsi, assign, GSI_NEW_STMT); + update_stmt(assign); + + rand_const = build_int_cstu(unsigned_intDI_type_node, get_random_const()); + assign = gimple_build_assign_with_ops(BIT_XOR_EXPR, local_entropy, local_entropy, rand_const); + gsi_insert_after(&gsi, assign, GSI_NEW_STMT); + update_stmt(assign); +} + +static unsigned int latent_entropy_execute(void) +{ + basic_block bb; + tree local_entropy; + + if (!latent_entropy_decl) { + varpool_node_ptr node; + + FOR_EACH_VARIABLE(node) { + tree var = NODE_DECL(node); + + if (DECL_NAME_LENGTH(var) < sizeof("latent_entropy") - 1) + continue; + if (strcmp(IDENTIFIER_POINTER(DECL_NAME(var)), "latent_entropy")) + continue; + latent_entropy_decl = var; + break; + } + if (!latent_entropy_decl) + return 0; + } + + gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun))); + bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)); + if (!single_pred_p(bb)) { + split_edge(single_succ_edge(ENTRY_BLOCK_PTR_FOR_FN(cfun))); + gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun))); + bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun)); + } + + /* create local entropy variable */ + local_entropy = create_a_tmp_var(unsigned_intDI_type_node, "local_entropy"); + + /* 1. stack pointer */ + mix_in_sp(bb, local_entropy); + + bb = bb->next_bb; + /* 2. instrument each BB with an operation on the local entropy variable */ + while (bb != EXIT_BLOCK_PTR_FOR_FN(cfun)) { + perturb_local_entropy(bb, local_entropy); + bb = bb->next_bb; + }; + + /* 3. mix local entropy into the global entropy variable */ + gcc_assert(single_pred_p(EXIT_BLOCK_PTR_FOR_FN(cfun))); + perturb_latent_entropy(single_pred(EXIT_BLOCK_PTR_FOR_FN(cfun)), local_entropy); + return 0; +} + +static void latent_entropy_start_unit(void *gcc_data __unused, void *user_data __unused) +{ + tree latent_entropy_type; + + seed = get_random_seed(false); + + if (in_lto_p) + return; + + /* extern volatile u64 latent_entropy */ + gcc_assert(TYPE_PRECISION(long_long_unsigned_type_node) == 64); + latent_entropy_type = build_qualified_type(long_long_unsigned_type_node, TYPE_QUALS(long_long_unsigned_type_node) | TYPE_QUAL_VOLATILE); + latent_entropy_decl = build_decl(UNKNOWN_LOCATION, VAR_DECL, get_identifier("latent_entropy"), latent_entropy_type); + + TREE_STATIC(latent_entropy_decl) = 1; + TREE_PUBLIC(latent_entropy_decl) = 1; + TREE_USED(latent_entropy_decl) = 1; + DECL_PRESERVE_P(latent_entropy_decl) = 1; + TREE_THIS_VOLATILE(latent_entropy_decl) = 1; + DECL_EXTERNAL(latent_entropy_decl) = 1; + DECL_ARTIFICIAL(latent_entropy_decl) = 1; + lang_hooks.decls.pushdecl(latent_entropy_decl); +} + +#define PASS_NAME latent_entropy +#define PROPERTIES_REQUIRED PROP_gimple_leh | PROP_cfg +#define TODO_FLAGS_FINISH TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func | TODO_update_ssa +#include "gcc-generate-gimple-pass.h" + +int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version) +{ + const char * const plugin_name = plugin_info->base_name; + const int argc = plugin_info->argc; + const struct plugin_argument * const argv = plugin_info->argv; + int i; + + struct register_pass_info latent_entropy_pass_info; + + latent_entropy_pass_info.pass = make_latent_entropy_pass(); + latent_entropy_pass_info.reference_pass_name = "optimized"; + latent_entropy_pass_info.ref_pass_instance_number = 1; + latent_entropy_pass_info.pos_op = PASS_POS_INSERT_BEFORE; + static const struct ggc_root_tab gt_ggc_r_gt_latent_entropy[] = { + { + .base = &latent_entropy_decl, + .nelt = 1, + .stride = sizeof(latent_entropy_decl), + .cb = >_ggc_mx_tree_node, + .pchw = >_pch_nx_tree_node + }, + LAST_GGC_ROOT_TAB + }; + + if (!plugin_default_version_check(version, &gcc_version)) { + error(G_("incompatible gcc/plugin versions")); + return 1; + } + + for (i = 0; i < argc; ++i) { + if (!(strcmp(argv[i].key, "disable"))) { + enabled = false; + continue; + } + error(G_("unkown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key); + } + + register_callback(plugin_name, PLUGIN_INFO, NULL, &latent_entropy_plugin_info); + if (enabled) { + register_callback(plugin_name, PLUGIN_START_UNIT, &latent_entropy_start_unit, NULL); + register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS, NULL, (void *)>_ggc_r_gt_latent_entropy); + register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL, &latent_entropy_pass_info); + } + register_callback(plugin_name, PLUGIN_ATTRIBUTES, register_attributes, NULL); + + return 0; +} -- 2.8.1 ^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [PATCH v1 1/3] Add the latent_entropy gcc plugin 2016-05-23 22:15 ` [PATCH v1 1/3] Add " Emese Revfy @ 2016-05-24 17:32 ` Kees Cook 2016-05-24 21:23 ` Emese Revfy 2016-05-24 23:40 ` PaX Team 0 siblings, 2 replies; 14+ messages in thread From: Kees Cook @ 2016-05-24 17:32 UTC (permalink / raw) To: Emese Revfy Cc: kernel-hardening, PaX Team, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On Mon, May 23, 2016 at 3:15 PM, Emese Revfy <re.emese@gmail.com> wrote: > This plugin mitigates the problem of the kernel having too little entropy during > and after boot for generating crypto keys. > > It creates a local variable in every marked function. The value of this variable is > modified by randomly chosen operations (add, xor and rol) and > random values (gcc generates them at compile time and the stack pointer at runtime). > It depends on the control flow (e.g., loops, conditions). > > Before the function returns the plugin writes this local variable > into the latent_entropy global variable. The value of this global variable is > added to the kernel entropy pool in do_one_initcall() and _do_fork(). I'm excited to see this! This looks like it'll help a lot with early entropy, which is something that'll be a problem for some architectures that are trying to do early randomish things (e.g. the heap layout randomization, various canaries, etc). Do you have any good examples of a before/after case of early randomness being fixed by this? > Based on work created by the PaX Team. > > Signed-off-by: Emese Revfy <re.emese@gmail.com> > --- > arch/Kconfig | 17 ++ > arch/powerpc/kernel/Makefile | 8 +- > include/linux/random.h | 8 + > init/main.c | 1 + > kernel/fork.c | 1 + > mm/page_alloc.c | 5 + > scripts/Makefile.gcc-plugins | 10 +- > scripts/gcc-plugins/Makefile | 1 + > scripts/gcc-plugins/latent_entropy_plugin.c | 446 ++++++++++++++++++++++++++++ > 9 files changed, 491 insertions(+), 6 deletions(-) > create mode 100644 scripts/gcc-plugins/latent_entropy_plugin.c > > diff --git a/arch/Kconfig b/arch/Kconfig > index 5feadad..74489df 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -393,6 +393,23 @@ config GCC_PLUGIN_SANCOV > gcc-4.5 on). It is based on the commit "Add fuzzing coverage support" > by Dmitry Vyukov <dvyukov@google.com>. > > +config GCC_PLUGIN_LATENT_ENTROPY > + bool "latent entropy" > + depends on GCC_PLUGINS > + help > + By saying Y here the kernel will instrument some kernel code to > + extract some entropy from both original and artificially created > + program state. This will help especially embedded systems where > + there is little 'natural' source of entropy normally. The cost > + is some slowdown of the boot process and fork and irq processing. Can "some" be more well quantified? > + > + Note that entropy extracted this way is not known to be cryptographically > + secure! maybe add ", but should be good enough for canaries and other secrets." ? > + > + This plugin was ported from grsecurity/PaX. More information at: > + * https://grsecurity.net/ > + * https://pax.grsecurity.net/ > + > config HAVE_CC_STACKPROTECTOR > bool > help > diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile > index 2da380f..6c7e448 100644 > --- a/arch/powerpc/kernel/Makefile > +++ b/arch/powerpc/kernel/Makefile > @@ -16,10 +16,10 @@ endif > > ifdef CONFIG_FUNCTION_TRACER > # Do not trace early boot code > -CFLAGS_REMOVE_cputable.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) > -CFLAGS_REMOVE_prom_init.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) > -CFLAGS_REMOVE_btext.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) > -CFLAGS_REMOVE_prom.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) > +CFLAGS_REMOVE_cputable.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) $(DISABLE_LATENT_ENTROPY_PLUGIN) > +CFLAGS_REMOVE_prom_init.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) $(DISABLE_LATENT_ENTROPY_PLUGIN) > +CFLAGS_REMOVE_btext.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) $(DISABLE_LATENT_ENTROPY_PLUGIN) > +CFLAGS_REMOVE_prom.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) $(DISABLE_LATENT_ENTROPY_PLUGIN) > # do not trace tracer code > CFLAGS_REMOVE_ftrace.o = -mno-sched-epilog $(CC_FLAGS_FTRACE) > # timers used by tracing > diff --git a/include/linux/random.h b/include/linux/random.h > index e47e533..379f4bc 100644 > --- a/include/linux/random.h > +++ b/include/linux/random.h > @@ -18,6 +18,14 @@ struct random_ready_callback { > }; > > extern void add_device_randomness(const void *, unsigned int); > + > +static inline void add_latent_entropy(void) > +{ > +#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY > + add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); > +#endif > +} > + Traditionally the code style of #ifdef arrangement in header files uses an "#else" since there's usually other code to wrap in it, and it results in small future diffs: #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY static inline void add_latent_entropy(void) { add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); } #else static inline void add_latent_entropy(void) { } #endif Also, does this matter that it's non-atomic? It seems like the u64 below is being written to by multiple threads and even read by multiple threads. Am I misunderstanding something? > [...] > new file mode 100644 > index 0000000..7295c39 > --- /dev/null > +++ b/scripts/gcc-plugins/latent_entropy_plugin.c I feel like most of the functions in this plugin could use some more comments about what each one does. -Kees -- Kees Cook Chrome OS & Brillo Security ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v1 1/3] Add the latent_entropy gcc plugin 2016-05-24 17:32 ` Kees Cook @ 2016-05-24 21:23 ` Emese Revfy 2016-05-24 23:40 ` PaX Team 1 sibling, 0 replies; 14+ messages in thread From: Emese Revfy @ 2016-05-24 21:23 UTC (permalink / raw) To: Kees Cook Cc: kernel-hardening, PaX Team, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On Tue, 24 May 2016 10:32:15 -0700 Kees Cook <keescook@chromium.org> wrote: > Also, does this matter that it's non-atomic? It seems like the u64 > below is being written to by multiple threads and even read by > multiple threads. Am I misunderstanding something? The non-atomic accesses are intentional because they can extract more latent entropy from these data races. > > [...] > > new file mode 100644 > > index 0000000..7295c39 > > --- /dev/null > > +++ b/scripts/gcc-plugins/latent_entropy_plugin.c > > I feel like most of the functions in this plugin could use some more > comments about what each one does. I think the important parts are commented (most parts just use the gcc API). Where would you like more comments? -- Emese ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v1 1/3] Add the latent_entropy gcc plugin 2016-05-24 17:32 ` Kees Cook 2016-05-24 21:23 ` Emese Revfy @ 2016-05-24 23:40 ` PaX Team 2016-05-25 2:55 ` Kees Cook 1 sibling, 1 reply; 14+ messages in thread From: PaX Team @ 2016-05-24 23:40 UTC (permalink / raw) To: Emese Revfy, Kees Cook Cc: kernel-hardening, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On 24 May 2016 at 10:32, Kees Cook wrote: > On Mon, May 23, 2016 at 3:15 PM, Emese Revfy <re.emese@gmail.com> wrote: > > This plugin mitigates the problem of the kernel having too little entropy during > > and after boot for generating crypto keys. > > > I'm excited to see this! This looks like it'll help a lot with early > entropy, which is something that'll be a problem for some > architectures that are trying to do early randomish things (e.g. the > heap layout randomization, various canaries, etc). > > Do you have any good examples of a before/after case of early > randomness being fixed by this? unfortunately, i don't know of a way to quantify this kind of PRNG as the effective algorithm is not something simple and well-structured for which we have theories and tools to analyze already. of course this cuts both ways, an attacker faces the same barrier of non-analyzability. what can at most be observed is the state of the latent_entropy global variable after init across many boots but that'd provide a rather low and useless lower estimate only (e.g., up to 20 bits for a million reboots, or 30 bits for a billion reboots, etc). to answer your question, i'd like to believe that there's enough latent entropy in program state that can be harnessed to (re)seed the entropy pool but we'll probably never know just how well we are doing it so accounting for it and claiming 'fixed' will stay in the realm of wishful thinking i'm afraid. cheers, PaX Team ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v1 1/3] Add the latent_entropy gcc plugin 2016-05-24 23:40 ` PaX Team @ 2016-05-25 2:55 ` Kees Cook 2016-05-30 22:39 ` Emese Revfy 0 siblings, 1 reply; 14+ messages in thread From: Kees Cook @ 2016-05-25 2:55 UTC (permalink / raw) To: PaX Team Cc: Emese Revfy, kernel-hardening, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On Tue, May 24, 2016 at 4:40 PM, PaX Team <pageexec@freemail.hu> wrote: > On 24 May 2016 at 10:32, Kees Cook wrote: > >> On Mon, May 23, 2016 at 3:15 PM, Emese Revfy <re.emese@gmail.com> wrote: >> > This plugin mitigates the problem of the kernel having too little entropy during >> > and after boot for generating crypto keys. >> > >> I'm excited to see this! This looks like it'll help a lot with early >> entropy, which is something that'll be a problem for some >> architectures that are trying to do early randomish things (e.g. the >> heap layout randomization, various canaries, etc). >> >> Do you have any good examples of a before/after case of early >> randomness being fixed by this? > > unfortunately, i don't know of a way to quantify this kind of PRNG as the effective > algorithm is not something simple and well-structured for which we have theories and > tools to analyze already. of course this cuts both ways, an attacker faces the same > barrier of non-analyzability. > > what can at most be observed is the state of the latent_entropy global variable after > init across many boots but that'd provide a rather low and useless lower estimate only > (e.g., up to 20 bits for a million reboots, or 30 bits for a billion reboots, etc). > > to answer your question, i'd like to believe that there's enough latent entropy in > program state that can be harnessed to (re)seed the entropy pool but we'll probably > never know just how well we are doing it so accounting for it and claiming 'fixed' > will stay in the realm of wishful thinking i'm afraid. Yeah, answering "how random is this?" is not easy, but that's not what I meant. I'm more curious about specific build configs or hardware where calling get_random_int() early enough would always produce the same value (or the same value across all threads, etc), and in these cases, the new entropy should be visible when using the latent entropy plugin. -Kees -- Kees Cook Chrome OS & Brillo Security ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v1 1/3] Add the latent_entropy gcc plugin 2016-05-25 2:55 ` Kees Cook @ 2016-05-30 22:39 ` Emese Revfy 0 siblings, 0 replies; 14+ messages in thread From: Emese Revfy @ 2016-05-30 22:39 UTC (permalink / raw) To: Kees Cook Cc: PaX Team, kernel-hardening, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On Tue, 24 May 2016 19:55:17 -0700 Kees Cook <keescook@chromium.org> wrote: > Yeah, answering "how random is this?" is not easy, but that's not what > I meant. I'm more curious about specific build configs or hardware > where calling get_random_int() early enough would always produce the > same value (or the same value across all threads, etc), and in these > cases, the new entropy should be visible when using the latent entropy > plugin. I booted minimal configs (not allnoconfig because it can't boot in qemu) many times. I couldn't produce same values. -- Emese ^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v1 2/3] Mark functions with the latent_entropy attribute 2016-05-23 22:14 [PATCH v1 0/3] Introduce the latent_entropy gcc plugin Emese Revfy 2016-05-23 22:15 ` [PATCH v1 1/3] Add " Emese Revfy @ 2016-05-23 22:16 ` Emese Revfy 2016-05-24 17:16 ` Kees Cook 2016-05-23 22:17 ` [PATCH v1 3/3] Add the extra_latent_entropy kernel parameter Emese Revfy 2 siblings, 1 reply; 14+ messages in thread From: Emese Revfy @ 2016-05-23 22:16 UTC (permalink / raw) To: kernel-hardening Cc: pageexec, spender, mmarek, keescook, linux-kernel, yamada.masahiro, linux-kbuild, tytso, akpm, linux-mm, axboe, viro, paulmck, mingo, tglx, bart.vanassche, davem These functions have been selected because they are init functions or are called at random times or they have variable loops. Based on work created by the PaX Team. Signed-off-by: Emese Revfy <re.emese@gmail.com> --- block/blk-softirq.c | 2 +- drivers/char/random.c | 6 +++--- fs/namespace.c | 2 +- include/linux/compiler-gcc.h | 5 +++++ include/linux/compiler.h | 4 ++++ include/linux/fdtable.h | 2 +- include/linux/genhd.h | 2 +- include/linux/init.h | 10 ++++++++-- include/linux/random.h | 4 ++-- kernel/fork.c | 4 ++-- kernel/rcu/tiny.c | 2 +- kernel/rcu/tree.c | 2 +- kernel/sched/fair.c | 2 +- kernel/softirq.c | 4 ++-- kernel/time/timer.c | 2 +- lib/irq_poll.c | 2 +- lib/random32.c | 2 +- mm/page_alloc.c | 2 +- net/core/dev.c | 4 ++-- 19 files changed, 39 insertions(+), 24 deletions(-) diff --git a/block/blk-softirq.c b/block/blk-softirq.c index 53b1737..489eab8 100644 --- a/block/blk-softirq.c +++ b/block/blk-softirq.c @@ -18,7 +18,7 @@ static DEFINE_PER_CPU(struct list_head, blk_cpu_done); * Softirq action handler - move entries to local list and loop over them * while passing them to the queue registered handler. */ -static void blk_done_softirq(struct softirq_action *h) +static __latent_entropy void blk_done_softirq(struct softirq_action *h) { struct list_head *cpu_list, local_list; diff --git a/drivers/char/random.c b/drivers/char/random.c index 0158d3b..6cca3ed 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -443,9 +443,9 @@ struct entropy_store { }; static void push_to_pool(struct work_struct *work); -static __u32 input_pool_data[INPUT_POOL_WORDS]; -static __u32 blocking_pool_data[OUTPUT_POOL_WORDS]; -static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS]; +static __u32 input_pool_data[INPUT_POOL_WORDS] __latent_entropy; +static __u32 blocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy; +static __u32 nonblocking_pool_data[OUTPUT_POOL_WORDS] __latent_entropy; static struct entropy_store input_pool = { .poolinfo = &poolinfo_table[0], diff --git a/fs/namespace.c b/fs/namespace.c index 4fb1691..eed930c 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2778,7 +2778,7 @@ static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns) return new_ns; } -struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, +__latent_entropy struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, struct user_namespace *user_ns, struct fs_struct *new_fs) { struct mnt_namespace *new_ns; diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index e294939..8d85907 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -188,6 +188,11 @@ #endif /* GCC_VERSION >= 40300 */ #if GCC_VERSION >= 40500 + +#ifdef LATENT_ENTROPY_PLUGIN +#define __latent_entropy __attribute__((latent_entropy)) +#endif + /* * Mark a position in code as unreachable. This can be used to * suppress control flow warnings after asm blocks that transfer diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 793c082..c65327b 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -425,6 +425,10 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s # define __attribute_const__ /* unimplemented */ #endif +#ifndef __latent_entropy +# define __latent_entropy +#endif + /* * Tell gcc if a function is cold. The compiler will assume any path * directly leading to the call is unlikely. diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index 5295535..9852c7e 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -105,7 +105,7 @@ struct files_struct *get_files_struct(struct task_struct *); void put_files_struct(struct files_struct *fs); void reset_files_struct(struct files_struct *); int unshare_files(struct files_struct **); -struct files_struct *dup_fd(struct files_struct *, int *); +struct files_struct *dup_fd(struct files_struct *, int *) __latent_entropy; void do_close_on_exec(struct files_struct *); int iterate_fd(struct files_struct *, unsigned, int (*)(const void *, struct file *, unsigned), diff --git a/include/linux/genhd.h b/include/linux/genhd.h index 359a8e4..8736c1f 100644 --- a/include/linux/genhd.h +++ b/include/linux/genhd.h @@ -433,7 +433,7 @@ extern void disk_flush_events(struct gendisk *disk, unsigned int mask); extern unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask); /* drivers/char/random.c */ -extern void add_disk_randomness(struct gendisk *disk); +extern void add_disk_randomness(struct gendisk *disk) __latent_entropy; extern void rand_initialize_disk(struct gendisk *disk); static inline sector_t get_start_sect(struct block_device *bdev) diff --git a/include/linux/init.h b/include/linux/init.h index aedb254..68df2c3 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -37,9 +37,15 @@ * section. */ +#ifdef CONFIG_MEMORY_HOTPLUG +#define add_meminit_latent_entropy +#else +#define add_meminit_latent_entropy __latent_entropy +#endif + /* These are for everybody (although not all archs will actually discard it in modules) */ -#define __init __section(.init.text) __cold notrace +#define __init __section(.init.text) __cold notrace __latent_entropy #define __initdata __section(.init.data) #define __initconst __constsection(.init.rodata) #define __exitdata __section(.exit.data) @@ -92,7 +98,7 @@ #define __exit __section(.exit.text) __exitused __cold notrace /* Used for MEMORY_HOTPLUG */ -#define __meminit __section(.meminit.text) __cold notrace +#define __meminit __section(.meminit.text) __cold notrace add_meminit_latent_entropy #define __meminitdata __section(.meminit.data) #define __meminitconst __constsection(.meminit.rodata) #define __memexit __section(.memexit.text) __exitused __cold notrace diff --git a/include/linux/random.h b/include/linux/random.h index 379f4bc..9fb07d1 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -27,8 +27,8 @@ static inline void add_latent_entropy(void) } extern void add_input_randomness(unsigned int type, unsigned int code, - unsigned int value); -extern void add_interrupt_randomness(int irq, int irq_flags); + unsigned int value) __latent_entropy; +extern void add_interrupt_randomness(int irq, int irq_flags) __latent_entropy; extern void get_random_bytes(void *buf, int nbytes); extern int add_random_ready_callback(struct random_ready_callback *rdy); diff --git a/kernel/fork.c b/kernel/fork.c index d07d5a6..9fba65c 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -406,7 +406,7 @@ free_tsk: } #ifdef CONFIG_MMU -static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) +static __latent_entropy int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) { struct vm_area_struct *mpnt, *tmp, *prev, **pprev; struct rb_node **rb_link, *rb_parent; @@ -1281,7 +1281,7 @@ init_task_pid(struct task_struct *task, enum pid_type type, struct pid *pid) * parts of the process environment (as per the clone * flags). The actual kick-off is left to the caller. */ -static struct task_struct *copy_process(unsigned long clone_flags, +static __latent_entropy struct task_struct *copy_process(unsigned long clone_flags, unsigned long stack_start, unsigned long stack_size, int __user *child_tidptr, diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index 944b1b4..1898559 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -170,7 +170,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) false)); } -static void rcu_process_callbacks(struct softirq_action *unused) +static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) { __rcu_process_callbacks(&rcu_sched_ctrlblk); __rcu_process_callbacks(&rcu_bh_ctrlblk); diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index c7f1bc4..8821fce 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3004,7 +3004,7 @@ __rcu_process_callbacks(struct rcu_state *rsp) /* * Do RCU core processing for the current CPU. */ -static void rcu_process_callbacks(struct softirq_action *unused) +static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) { struct rcu_state *rsp; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 218f8e8..cd745c2 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8205,7 +8205,7 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { } * run_rebalance_domains is triggered when needed from the scheduler tick. * Also triggered for nohz idle balancing (with nohz_balancing_kick set). */ -static void run_rebalance_domains(struct softirq_action *h) +static __latent_entropy void run_rebalance_domains(struct softirq_action *h) { struct rq *this_rq = this_rq(); enum cpu_idle_type idle = this_rq->idle_balance ? diff --git a/kernel/softirq.c b/kernel/softirq.c index 17caf4b..34033fd 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -482,7 +482,7 @@ void __tasklet_hi_schedule_first(struct tasklet_struct *t) } EXPORT_SYMBOL(__tasklet_hi_schedule_first); -static void tasklet_action(struct softirq_action *a) +static __latent_entropy void tasklet_action(struct softirq_action *a) { struct tasklet_struct *list; @@ -518,7 +518,7 @@ static void tasklet_action(struct softirq_action *a) } } -static void tasklet_hi_action(struct softirq_action *a) +static __latent_entropy void tasklet_hi_action(struct softirq_action *a) { struct tasklet_struct *list; diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 3a95f97..6008e7ae 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -1414,7 +1414,7 @@ void update_process_times(int user_tick) /* * This function runs timers and the timer-tq in bottom half context. */ -static void run_timer_softirq(struct softirq_action *h) +static __latent_entropy void run_timer_softirq(struct softirq_action *h) { struct tvec_base *base = this_cpu_ptr(&tvec_bases); diff --git a/lib/irq_poll.c b/lib/irq_poll.c index 836f7db..63be749 100644 --- a/lib/irq_poll.c +++ b/lib/irq_poll.c @@ -74,7 +74,7 @@ void irq_poll_complete(struct irq_poll *iop) } EXPORT_SYMBOL(irq_poll_complete); -static void irq_poll_softirq(struct softirq_action *h) +static void __latent_entropy irq_poll_softirq(struct softirq_action *h) { struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll); int rearm = 0, budget = irq_poll_budget; diff --git a/lib/random32.c b/lib/random32.c index 510d1ce..722d2b6 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -47,7 +47,7 @@ static inline void prandom_state_selftest(void) } #endif -static DEFINE_PER_CPU(struct rnd_state, net_rand_state); +static DEFINE_PER_CPU(struct rnd_state, net_rand_state) __latent_entropy; /** * prandom_u32_state - seeded pseudo-random number generator. diff --git a/mm/page_alloc.c b/mm/page_alloc.c index d10324e..ffc4f4a 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1235,7 +1235,7 @@ static void __free_pages_ok(struct page *page, unsigned int order) } #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY -volatile u64 latent_entropy; +volatile u64 latent_entropy __latent_entropy; EXPORT_SYMBOL(latent_entropy); #endif diff --git a/net/core/dev.c b/net/core/dev.c index 904ff43..723d3af 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -3851,7 +3851,7 @@ int netif_rx_ni(struct sk_buff *skb) } EXPORT_SYMBOL(netif_rx_ni); -static void net_tx_action(struct softirq_action *h) +static __latent_entropy void net_tx_action(struct softirq_action *h) { struct softnet_data *sd = this_cpu_ptr(&softnet_data); @@ -5175,7 +5175,7 @@ out_unlock: return work; } -static void net_rx_action(struct softirq_action *h) +static __latent_entropy void net_rx_action(struct softirq_action *h) { struct softnet_data *sd = this_cpu_ptr(&softnet_data); unsigned long time_limit = jiffies + 2; -- 2.8.1 ^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [PATCH v1 2/3] Mark functions with the latent_entropy attribute 2016-05-23 22:16 ` [PATCH v1 2/3] Mark functions with the latent_entropy attribute Emese Revfy @ 2016-05-24 17:16 ` Kees Cook 2016-05-24 20:45 ` Emese Revfy 0 siblings, 1 reply; 14+ messages in thread From: Kees Cook @ 2016-05-24 17:16 UTC (permalink / raw) To: Emese Revfy Cc: kernel-hardening, PaX Team, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On Mon, May 23, 2016 at 3:16 PM, Emese Revfy <re.emese@gmail.com> wrote: > These functions have been selected because they are init functions or > are called at random times or they have variable loops. > > Based on work created by the PaX Team. > > Signed-off-by: Emese Revfy <re.emese@gmail.com> > [...] > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -188,6 +188,11 @@ > #endif /* GCC_VERSION >= 40300 */ > > #if GCC_VERSION >= 40500 > + > +#ifdef LATENT_ENTROPY_PLUGIN > +#define __latent_entropy __attribute__((latent_entropy)) > +#endif This deserves a full comment above it to describe its purpose and use for when people go trying to figure out what it is and where to use it. The commit message is a bit terse, so I'd try to expand both to describe what function characteristics a developer should look for to mark something with __latent_entropy. > + > /* > * Mark a position in code as unreachable. This can be used to > * suppress control flow warnings after asm blocks that transfer > [...] > diff --git a/include/linux/init.h b/include/linux/init.h > index aedb254..68df2c3 100644 > --- a/include/linux/init.h > +++ b/include/linux/init.h > @@ -37,9 +37,15 @@ > * section. > */ > > +#ifdef CONFIG_MEMORY_HOTPLUG > +#define add_meminit_latent_entropy > +#else > +#define add_meminit_latent_entropy __latent_entropy > +#endif > + > /* These are for everybody (although not all archs will actually > discard it in modules) */ > -#define __init __section(.init.text) __cold notrace > +#define __init __section(.init.text) __cold notrace __latent_entropy > #define __initdata __section(.init.data) > #define __initconst __constsection(.init.rodata) > #define __exitdata __section(.exit.data) > @@ -92,7 +98,7 @@ > #define __exit __section(.exit.text) __exitused __cold notrace > > /* Used for MEMORY_HOTPLUG */ > -#define __meminit __section(.meminit.text) __cold notrace > +#define __meminit __section(.meminit.text) __cold notrace add_meminit_latent_entropy > #define __meminitdata __section(.meminit.data) > #define __meminitconst __constsection(.meminit.rodata) > #define __memexit __section(.memexit.text) __exitused __cold notrace I was confused by these defines. :) Maybe "add_meminit_latent_entropy" should be named "__memory_hotplug_only_latent_entropy" or something like that? -Kees -- Kees Cook Chrome OS & Brillo Security ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v1 2/3] Mark functions with the latent_entropy attribute 2016-05-24 17:16 ` Kees Cook @ 2016-05-24 20:45 ` Emese Revfy 2016-05-24 20:55 ` Kees Cook 0 siblings, 1 reply; 14+ messages in thread From: Emese Revfy @ 2016-05-24 20:45 UTC (permalink / raw) To: Kees Cook Cc: kernel-hardening, PaX Team, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On Tue, 24 May 2016 10:16:09 -0700 Kees Cook <keescook@chromium.org> wrote: > On Mon, May 23, 2016 at 3:16 PM, Emese Revfy <re.emese@gmail.com> wrote: > > +#ifdef CONFIG_MEMORY_HOTPLUG > > +#define add_meminit_latent_entropy > > +#else > > +#define add_meminit_latent_entropy __latent_entropy > > +#endif > > + > > /* These are for everybody (although not all archs will actually > > discard it in modules) */ > > -#define __init __section(.init.text) __cold notrace > > +#define __init __section(.init.text) __cold notrace __latent_entropy > > #define __initdata __section(.init.data) > > #define __initconst __constsection(.init.rodata) > > #define __exitdata __section(.exit.data) > > @@ -92,7 +98,7 @@ > > #define __exit __section(.exit.text) __exitused __cold notrace > > > > /* Used for MEMORY_HOTPLUG */ > > -#define __meminit __section(.meminit.text) __cold notrace > > +#define __meminit __section(.meminit.text) __cold notrace add_meminit_latent_entropy > > #define __meminitdata __section(.meminit.data) > > #define __meminitconst __constsection(.meminit.rodata) > > #define __memexit __section(.memexit.text) __exitused __cold notrace > > I was confused by these defines. :) Maybe "add_meminit_latent_entropy" > should be named "__memory_hotplug_only_latent_entropy" or something > like that? I think the plugin doesn't cause a significant slowdown when CONFIG_MEMORY_HOTPLUG is enabled so I would rather always add the __latent_entropy attribute to __meminit. -- Emese ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v1 2/3] Mark functions with the latent_entropy attribute 2016-05-24 20:45 ` Emese Revfy @ 2016-05-24 20:55 ` Kees Cook 0 siblings, 0 replies; 14+ messages in thread From: Kees Cook @ 2016-05-24 20:55 UTC (permalink / raw) To: Emese Revfy Cc: kernel-hardening, PaX Team, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On Tue, May 24, 2016 at 1:45 PM, Emese Revfy <re.emese@gmail.com> wrote: > On Tue, 24 May 2016 10:16:09 -0700 > Kees Cook <keescook@chromium.org> wrote: > >> On Mon, May 23, 2016 at 3:16 PM, Emese Revfy <re.emese@gmail.com> wrote: >> > +#ifdef CONFIG_MEMORY_HOTPLUG >> > +#define add_meminit_latent_entropy >> > +#else >> > +#define add_meminit_latent_entropy __latent_entropy >> > +#endif >> > + >> > /* These are for everybody (although not all archs will actually >> > discard it in modules) */ >> > -#define __init __section(.init.text) __cold notrace >> > +#define __init __section(.init.text) __cold notrace __latent_entropy >> > #define __initdata __section(.init.data) >> > #define __initconst __constsection(.init.rodata) >> > #define __exitdata __section(.exit.data) >> > @@ -92,7 +98,7 @@ >> > #define __exit __section(.exit.text) __exitused __cold notrace >> > >> > /* Used for MEMORY_HOTPLUG */ >> > -#define __meminit __section(.meminit.text) __cold notrace >> > +#define __meminit __section(.meminit.text) __cold notrace add_meminit_latent_entropy >> > #define __meminitdata __section(.meminit.data) >> > #define __meminitconst __constsection(.meminit.rodata) >> > #define __memexit __section(.memexit.text) __exitused __cold notrace >> >> I was confused by these defines. :) Maybe "add_meminit_latent_entropy" >> should be named "__memory_hotplug_only_latent_entropy" or something >> like that? > > I think the plugin doesn't cause a significant slowdown when CONFIG_MEMORY_HOTPLUG is enabled so I would rather always add the __latent_entropy attribute to __meminit. That seems fine to me. :) -Kees -- Kees Cook Chrome OS & Brillo Security ^ permalink raw reply [flat|nested] 14+ messages in thread
* [PATCH v1 3/3] Add the extra_latent_entropy kernel parameter 2016-05-23 22:14 [PATCH v1 0/3] Introduce the latent_entropy gcc plugin Emese Revfy 2016-05-23 22:15 ` [PATCH v1 1/3] Add " Emese Revfy 2016-05-23 22:16 ` [PATCH v1 2/3] Mark functions with the latent_entropy attribute Emese Revfy @ 2016-05-23 22:17 ` Emese Revfy 2016-05-24 17:09 ` Kees Cook 2 siblings, 1 reply; 14+ messages in thread From: Emese Revfy @ 2016-05-23 22:17 UTC (permalink / raw) To: kernel-hardening Cc: pageexec, spender, mmarek, keescook, linux-kernel, yamada.masahiro, linux-kbuild, tytso, akpm, linux-mm, axboe, viro, paulmck, mingo, tglx, bart.vanassche, davem When extra_latent_entropy is passed on the kernel command line, entropy will be extracted from up to the first 4GB of RAM while the runtime memory allocator is being initialized. Based on work created by the PaX Team. Signed-off-by: Emese Revfy <re.emese@gmail.com> --- Documentation/kernel-parameters.txt | 5 +++++ arch/Kconfig | 5 +++++ mm/page_alloc.c | 23 +++++++++++++++++++++++ 3 files changed, 33 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 5349363..6c2496e 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2862,6 +2862,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. the specified number of seconds. This is to be used if your oopses keep scrolling off the screen. + extra_latent_entropy + Enable a very simple form of latent entropy extraction + from the first 4GB of memory as the bootmem allocator + passes the memory pages to the buddy allocator. + pcbit= [HW,ISDN] pcd. [PARIDE] diff --git a/arch/Kconfig b/arch/Kconfig index 74489df..327d1e4 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -403,6 +403,11 @@ config GCC_PLUGIN_LATENT_ENTROPY there is little 'natural' source of entropy normally. The cost is some slowdown of the boot process and fork and irq processing. + When extra_latent_entropy is passed on the kernel command line, + entropy will be extracted from up to the first 4GB of RAM while the + runtime memory allocator is being initialized. This costs even more + slowdown of the boot process. + Note that entropy extracted this way is not known to be cryptographically secure! diff --git a/mm/page_alloc.c b/mm/page_alloc.c index ffc4f4a..c79407b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -63,6 +63,7 @@ #include <linux/sched/rt.h> #include <linux/page_owner.h> #include <linux/kthread.h> +#include <linux/random.h> #include <asm/sections.h> #include <asm/tlbflush.h> @@ -1235,6 +1236,15 @@ static void __free_pages_ok(struct page *page, unsigned int order) } #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY +bool __meminitdata extra_latent_entropy; + +static int __init setup_extra_latent_entropy(char *str) +{ + extra_latent_entropy = true; + return 0; +} +early_param("extra_latent_entropy", setup_extra_latent_entropy); + volatile u64 latent_entropy __latent_entropy; EXPORT_SYMBOL(latent_entropy); #endif @@ -1254,6 +1264,19 @@ static void __init __free_pages_boot_core(struct page *page, unsigned int order) __ClearPageReserved(p); set_page_count(p, 0); +#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY + if (extra_latent_entropy && !PageHighMem(page) && page_to_pfn(page) < 0x100000) { + u64 hash = 0; + size_t index, end = PAGE_SIZE * nr_pages / sizeof hash; + const u64 *data = lowmem_page_address(page); + + for (index = 0; index < end; index++) + hash ^= hash + data[index]; + latent_entropy ^= hash; + add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); + } +#endif + page_zone(page)->managed_pages += nr_pages; set_page_refcounted(page); __free_pages(page, order); -- 2.8.1 ^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [PATCH v1 3/3] Add the extra_latent_entropy kernel parameter 2016-05-23 22:17 ` [PATCH v1 3/3] Add the extra_latent_entropy kernel parameter Emese Revfy @ 2016-05-24 17:09 ` Kees Cook 2016-05-24 20:29 ` Emese Revfy 0 siblings, 1 reply; 14+ messages in thread From: Kees Cook @ 2016-05-24 17:09 UTC (permalink / raw) To: Emese Revfy Cc: kernel-hardening, PaX Team, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On Mon, May 23, 2016 at 3:17 PM, Emese Revfy <re.emese@gmail.com> wrote: > When extra_latent_entropy is passed on the kernel command line, > entropy will be extracted from up to the first 4GB of RAM while the > runtime memory allocator is being initialized. > > Based on work created by the PaX Team. > > Signed-off-by: Emese Revfy <re.emese@gmail.com> > --- > Documentation/kernel-parameters.txt | 5 +++++ > arch/Kconfig | 5 +++++ > mm/page_alloc.c | 23 +++++++++++++++++++++++ > 3 files changed, 33 insertions(+) > > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index 5349363..6c2496e 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2862,6 +2862,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > the specified number of seconds. This is to be used if > your oopses keep scrolling off the screen. > > + extra_latent_entropy > + Enable a very simple form of latent entropy extraction > + from the first 4GB of memory as the bootmem allocator > + passes the memory pages to the buddy allocator. > + > pcbit= [HW,ISDN] > > pcd. [PARIDE] > diff --git a/arch/Kconfig b/arch/Kconfig > index 74489df..327d1e4 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -403,6 +403,11 @@ config GCC_PLUGIN_LATENT_ENTROPY > there is little 'natural' source of entropy normally. The cost > is some slowdown of the boot process and fork and irq processing. > > + When extra_latent_entropy is passed on the kernel command line, > + entropy will be extracted from up to the first 4GB of RAM while the > + runtime memory allocator is being initialized. This costs even more > + slowdown of the boot process. > + > Note that entropy extracted this way is not known to be cryptographically > secure! > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index ffc4f4a..c79407b 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -63,6 +63,7 @@ > #include <linux/sched/rt.h> > #include <linux/page_owner.h> > #include <linux/kthread.h> > +#include <linux/random.h> > > #include <asm/sections.h> > #include <asm/tlbflush.h> > @@ -1235,6 +1236,15 @@ static void __free_pages_ok(struct page *page, unsigned int order) > } > > #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY > +bool __meminitdata extra_latent_entropy; > + > +static int __init setup_extra_latent_entropy(char *str) > +{ > + extra_latent_entropy = true; > + return 0; > +} > +early_param("extra_latent_entropy", setup_extra_latent_entropy); > + > volatile u64 latent_entropy __latent_entropy; > EXPORT_SYMBOL(latent_entropy); > #endif > @@ -1254,6 +1264,19 @@ static void __init __free_pages_boot_core(struct page *page, unsigned int order) > __ClearPageReserved(p); > set_page_count(p, 0); > > +#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY > + if (extra_latent_entropy && !PageHighMem(page) && page_to_pfn(page) < 0x100000) { > + u64 hash = 0; > + size_t index, end = PAGE_SIZE * nr_pages / sizeof hash; > + const u64 *data = lowmem_page_address(page); > + > + for (index = 0; index < end; index++) > + hash ^= hash + data[index]; > + latent_entropy ^= hash; > + add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); > + } > +#endif > + We try to minimize #ifdefs in the .c code, so in this case, I think I would define "extra_latent_entropy" during an #else above so this "if" can be culled by the compiler automatically: #else # define extra_latent_entropy false #endif Others may have better suggestions to avoid the second #ifdef, but this seems the cleanest way to me to tie this to the earlier #ifdef. -Kees > page_zone(page)->managed_pages += nr_pages; > set_page_refcounted(page); > __free_pages(page, order); > -- > 2.8.1 > -- Kees Cook Chrome OS & Brillo Security ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH v1 3/3] Add the extra_latent_entropy kernel parameter 2016-05-24 17:09 ` Kees Cook @ 2016-05-24 20:29 ` Emese Revfy 0 siblings, 0 replies; 14+ messages in thread From: Emese Revfy @ 2016-05-24 20:29 UTC (permalink / raw) To: Kees Cook Cc: kernel-hardening, PaX Team, Brad Spengler, Michal Marek, LKML, Masahiro Yamada, linux-kbuild, Theodore Ts'o, Andrew Morton, Linux-MM, Jens Axboe, Al Viro, Paul McKenney, Ingo Molnar, Thomas Gleixner, bart.vanassche, David S. Miller On Tue, 24 May 2016 10:09:16 -0700 Kees Cook <keescook@chromium.org> wrote: > On Mon, May 23, 2016 at 3:17 PM, Emese Revfy <re.emese@gmail.com> wrote: > > @@ -1235,6 +1236,15 @@ static void __free_pages_ok(struct page *page, unsigned int order) > > } > > > > #ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY > > +bool __meminitdata extra_latent_entropy; > > + > > +static int __init setup_extra_latent_entropy(char *str) > > +{ > > + extra_latent_entropy = true; > > + return 0; > > +} > > +early_param("extra_latent_entropy", setup_extra_latent_entropy); > > + > > volatile u64 latent_entropy __latent_entropy; > > EXPORT_SYMBOL(latent_entropy); > > #endif > > @@ -1254,6 +1264,19 @@ static void __init __free_pages_boot_core(struct page *page, unsigned int order) > > __ClearPageReserved(p); > > set_page_count(p, 0); > > > > +#ifdef CONFIG_GCC_PLUGIN_LATENT_ENTROPY > > + if (extra_latent_entropy && !PageHighMem(page) && page_to_pfn(page) < 0x100000) { > > + u64 hash = 0; > > + size_t index, end = PAGE_SIZE * nr_pages / sizeof hash; > > + const u64 *data = lowmem_page_address(page); > > + > > + for (index = 0; index < end; index++) > > + hash ^= hash + data[index]; > > + latent_entropy ^= hash; > > + add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy)); > > + } > > +#endif > > + > > We try to minimize #ifdefs in the .c code, so in this case, I think I > would define "extra_latent_entropy" during an #else above so this "if" > can be culled by the compiler automatically: > > #else > # define extra_latent_entropy false > #endif > > Others may have better suggestions to avoid the second #ifdef, but > this seems the cleanest way to me to tie this to the earlier #ifdef. Hi, I think the best way would be if I removed all #ifdefs because this is useful without the latent_entropy plugin. I don't know wether the default value of extra_latent_entropy should be true or false. I'll do some performance measurements. -- Emese ^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2016-05-30 22:33 UTC | newest] Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2016-05-23 22:14 [PATCH v1 0/3] Introduce the latent_entropy gcc plugin Emese Revfy 2016-05-23 22:15 ` [PATCH v1 1/3] Add " Emese Revfy 2016-05-24 17:32 ` Kees Cook 2016-05-24 21:23 ` Emese Revfy 2016-05-24 23:40 ` PaX Team 2016-05-25 2:55 ` Kees Cook 2016-05-30 22:39 ` Emese Revfy 2016-05-23 22:16 ` [PATCH v1 2/3] Mark functions with the latent_entropy attribute Emese Revfy 2016-05-24 17:16 ` Kees Cook 2016-05-24 20:45 ` Emese Revfy 2016-05-24 20:55 ` Kees Cook 2016-05-23 22:17 ` [PATCH v1 3/3] Add the extra_latent_entropy kernel parameter Emese Revfy 2016-05-24 17:09 ` Kees Cook 2016-05-24 20:29 ` Emese Revfy
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