Revision 0432a0a066b05361b6d4d26522233c3c76c9e5da authored by Linus Torvalds on 03 August 2019, 17:51:29 UTC, committed by Linus Torvalds on 03 August 2019, 17:51:29 UTC
Pull vdso timer fixes from Thomas Gleixner: "A series of commits to deal with the regression caused by the generic VDSO implementation. The usage of clock_gettime64() for 32bit compat fallback syscalls caused seccomp filters to kill innocent processes because they only allow clock_gettime(). Handle the compat syscalls with clock_gettime() as before, which is not a functional problem for the VDSO as the legacy compat application interface is not y2038 safe anyway. It's just extra fallback code which needs to be implemented on every architecture. It's opt in for now so that it does not break the compile of already converted architectures in linux-next. Once these are fixed, the #ifdeffery goes away. So much for trying to be smart and reuse code..." * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: arm64: compat: vdso: Use legacy syscalls as fallback x86/vdso/32: Use 32bit syscall fallback lib/vdso/32: Provide legacy syscall fallbacks lib/vdso: Move fallback invocation to the callers lib/vdso/32: Remove inconsistent NULL pointer checks
stackleak_plugin.c
/*
* Copyright 2011-2017 by the PaX Team <pageexec@freemail.hu>
* Modified by Alexander Popov <alex.popov@linux.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
*
* This gcc plugin is needed for tracking the lowest border of the kernel stack.
* It instruments the kernel code inserting stackleak_track_stack() calls:
* - after alloca();
* - for the functions with a stack frame size greater than or equal
* to the "track-min-size" plugin parameter.
*
* This plugin is ported from grsecurity/PaX. For more information see:
* https://grsecurity.net/
* https://pax.grsecurity.net/
*
* Debugging:
* - use fprintf() to stderr, debug_generic_expr(), debug_gimple_stmt(),
* print_rtl() and print_simple_rtl();
* - add "-fdump-tree-all -fdump-rtl-all" to the plugin CFLAGS in
* Makefile.gcc-plugins to see the verbose dumps of the gcc passes;
* - use gcc -E to understand the preprocessing shenanigans;
* - use gcc with enabled CFG/GIMPLE/SSA verification (--enable-checking).
*/
#include "gcc-common.h"
__visible int plugin_is_GPL_compatible;
static int track_frame_size = -1;
static const char track_function[] = "stackleak_track_stack";
/*
* Mark these global variables (roots) for gcc garbage collector since
* they point to the garbage-collected memory.
*/
static GTY(()) tree track_function_decl;
static struct plugin_info stackleak_plugin_info = {
.version = "201707101337",
.help = "track-min-size=nn\ttrack stack for functions with a stack frame size >= nn bytes\n"
"disable\t\tdo not activate the plugin\n"
};
static void stackleak_add_track_stack(gimple_stmt_iterator *gsi, bool after)
{
gimple stmt;
gcall *stackleak_track_stack;
cgraph_node_ptr node;
int frequency;
basic_block bb;
/* Insert call to void stackleak_track_stack(void) */
stmt = gimple_build_call(track_function_decl, 0);
stackleak_track_stack = as_a_gcall(stmt);
if (after) {
gsi_insert_after(gsi, stackleak_track_stack,
GSI_CONTINUE_LINKING);
} else {
gsi_insert_before(gsi, stackleak_track_stack, GSI_SAME_STMT);
}
/* Update the cgraph */
bb = gimple_bb(stackleak_track_stack);
node = cgraph_get_create_node(track_function_decl);
gcc_assert(node);
frequency = compute_call_stmt_bb_frequency(current_function_decl, bb);
cgraph_create_edge(cgraph_get_node(current_function_decl), node,
stackleak_track_stack, bb->count, frequency);
}
static bool is_alloca(gimple stmt)
{
if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA))
return true;
#if BUILDING_GCC_VERSION >= 4007
if (gimple_call_builtin_p(stmt, BUILT_IN_ALLOCA_WITH_ALIGN))
return true;
#endif
return false;
}
/*
* Work with the GIMPLE representation of the code. Insert the
* stackleak_track_stack() call after alloca() and into the beginning
* of the function if it is not instrumented.
*/
static unsigned int stackleak_instrument_execute(void)
{
basic_block bb, entry_bb;
bool prologue_instrumented = false, is_leaf = true;
gimple_stmt_iterator gsi;
/*
* ENTRY_BLOCK_PTR is a basic block which represents possible entry
* point of a function. This block does not contain any code and
* has a CFG edge to its successor.
*/
gcc_assert(single_succ_p(ENTRY_BLOCK_PTR_FOR_FN(cfun)));
entry_bb = single_succ(ENTRY_BLOCK_PTR_FOR_FN(cfun));
/*
* Loop through the GIMPLE statements in each of cfun basic blocks.
* cfun is a global variable which represents the function that is
* currently processed.
*/
FOR_EACH_BB_FN(bb, cfun) {
for (gsi = gsi_start_bb(bb); !gsi_end_p(gsi); gsi_next(&gsi)) {
gimple stmt;
stmt = gsi_stmt(gsi);
/* Leaf function is a function which makes no calls */
if (is_gimple_call(stmt))
is_leaf = false;
if (!is_alloca(stmt))
continue;
/* Insert stackleak_track_stack() call after alloca() */
stackleak_add_track_stack(&gsi, true);
if (bb == entry_bb)
prologue_instrumented = true;
}
}
if (prologue_instrumented)
return 0;
/*
* Special cases to skip the instrumentation.
*
* Taking the address of static inline functions materializes them,
* but we mustn't instrument some of them as the resulting stack
* alignment required by the function call ABI will break other
* assumptions regarding the expected (but not otherwise enforced)
* register clobbering ABI.
*
* Case in point: native_save_fl on amd64 when optimized for size
* clobbers rdx if it were instrumented here.
*
* TODO: any more special cases?
*/
if (is_leaf &&
!TREE_PUBLIC(current_function_decl) &&
DECL_DECLARED_INLINE_P(current_function_decl)) {
return 0;
}
if (is_leaf &&
!strncmp(IDENTIFIER_POINTER(DECL_NAME(current_function_decl)),
"_paravirt_", 10)) {
return 0;
}
/* Insert stackleak_track_stack() call at the function beginning */
bb = entry_bb;
if (!single_pred_p(bb)) {
/* gcc_assert(bb_loop_depth(bb) ||
(bb->flags & BB_IRREDUCIBLE_LOOP)); */
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));
}
gsi = gsi_after_labels(bb);
stackleak_add_track_stack(&gsi, false);
return 0;
}
static bool large_stack_frame(void)
{
#if BUILDING_GCC_VERSION >= 8000
return maybe_ge(get_frame_size(), track_frame_size);
#else
return (get_frame_size() >= track_frame_size);
#endif
}
/*
* Work with the RTL representation of the code.
* Remove the unneeded stackleak_track_stack() calls from the functions
* which don't call alloca() and don't have a large enough stack frame size.
*/
static unsigned int stackleak_cleanup_execute(void)
{
rtx_insn *insn, *next;
if (cfun->calls_alloca)
return 0;
if (large_stack_frame())
return 0;
/*
* Find stackleak_track_stack() calls. Loop through the chain of insns,
* which is an RTL representation of the code for a function.
*
* The example of a matching insn:
* (call_insn 8 4 10 2 (call (mem (symbol_ref ("stackleak_track_stack")
* [flags 0x41] <function_decl 0x7f7cd3302a80 stackleak_track_stack>)
* [0 stackleak_track_stack S1 A8]) (0)) 675 {*call} (expr_list
* (symbol_ref ("stackleak_track_stack") [flags 0x41] <function_decl
* 0x7f7cd3302a80 stackleak_track_stack>) (expr_list (0) (nil))) (nil))
*/
for (insn = get_insns(); insn; insn = next) {
rtx body;
next = NEXT_INSN(insn);
/* Check the expression code of the insn */
if (!CALL_P(insn))
continue;
/*
* Check the expression code of the insn body, which is an RTL
* Expression (RTX) describing the side effect performed by
* that insn.
*/
body = PATTERN(insn);
if (GET_CODE(body) == PARALLEL)
body = XVECEXP(body, 0, 0);
if (GET_CODE(body) != CALL)
continue;
/*
* Check the first operand of the call expression. It should
* be a mem RTX describing the needed subroutine with a
* symbol_ref RTX.
*/
body = XEXP(body, 0);
if (GET_CODE(body) != MEM)
continue;
body = XEXP(body, 0);
if (GET_CODE(body) != SYMBOL_REF)
continue;
if (SYMBOL_REF_DECL(body) != track_function_decl)
continue;
/* Delete the stackleak_track_stack() call */
delete_insn_and_edges(insn);
#if BUILDING_GCC_VERSION >= 4007 && BUILDING_GCC_VERSION < 8000
if (GET_CODE(next) == NOTE &&
NOTE_KIND(next) == NOTE_INSN_CALL_ARG_LOCATION) {
insn = next;
next = NEXT_INSN(insn);
delete_insn_and_edges(insn);
}
#endif
}
return 0;
}
static bool stackleak_gate(void)
{
tree section;
section = lookup_attribute("section",
DECL_ATTRIBUTES(current_function_decl));
if (section && TREE_VALUE(section)) {
section = TREE_VALUE(TREE_VALUE(section));
if (!strncmp(TREE_STRING_POINTER(section), ".init.text", 10))
return false;
if (!strncmp(TREE_STRING_POINTER(section), ".devinit.text", 13))
return false;
if (!strncmp(TREE_STRING_POINTER(section), ".cpuinit.text", 13))
return false;
if (!strncmp(TREE_STRING_POINTER(section), ".meminit.text", 13))
return false;
}
return track_frame_size >= 0;
}
/* Build the function declaration for stackleak_track_stack() */
static void stackleak_start_unit(void *gcc_data __unused,
void *user_data __unused)
{
tree fntype;
/* void stackleak_track_stack(void) */
fntype = build_function_type_list(void_type_node, NULL_TREE);
track_function_decl = build_fn_decl(track_function, fntype);
DECL_ASSEMBLER_NAME(track_function_decl); /* for LTO */
TREE_PUBLIC(track_function_decl) = 1;
TREE_USED(track_function_decl) = 1;
DECL_EXTERNAL(track_function_decl) = 1;
DECL_ARTIFICIAL(track_function_decl) = 1;
DECL_PRESERVE_P(track_function_decl) = 1;
}
/*
* Pass gate function is a predicate function that gets executed before the
* corresponding pass. If the return value is 'true' the pass gets executed,
* otherwise, it is skipped.
*/
static bool stackleak_instrument_gate(void)
{
return stackleak_gate();
}
#define PASS_NAME stackleak_instrument
#define PROPERTIES_REQUIRED PROP_gimple_leh | PROP_cfg
#define TODO_FLAGS_START TODO_verify_ssa | TODO_verify_flow | TODO_verify_stmts
#define TODO_FLAGS_FINISH TODO_verify_ssa | TODO_verify_stmts | TODO_dump_func \
| TODO_update_ssa | TODO_rebuild_cgraph_edges
#include "gcc-generate-gimple-pass.h"
static bool stackleak_cleanup_gate(void)
{
return stackleak_gate();
}
#define PASS_NAME stackleak_cleanup
#define TODO_FLAGS_FINISH TODO_dump_func
#include "gcc-generate-rtl-pass.h"
/*
* Every gcc plugin exports a plugin_init() function that is called right
* after the plugin is loaded. This function is responsible for registering
* the plugin callbacks and doing other required initialization.
*/
__visible 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 = 0;
/* Extra GGC root tables describing our GTY-ed data */
static const struct ggc_root_tab gt_ggc_r_gt_stackleak[] = {
{
.base = &track_function_decl,
.nelt = 1,
.stride = sizeof(track_function_decl),
.cb = >_ggc_mx_tree_node,
.pchw = >_pch_nx_tree_node
},
LAST_GGC_ROOT_TAB
};
/*
* The stackleak_instrument pass should be executed before the
* "optimized" pass, which is the control flow graph cleanup that is
* performed just before expanding gcc trees to the RTL. In former
* versions of the plugin this new pass was inserted before the
* "tree_profile" pass, which is currently called "profile".
*/
PASS_INFO(stackleak_instrument, "optimized", 1,
PASS_POS_INSERT_BEFORE);
/*
* The stackleak_cleanup pass should be executed before the "*free_cfg"
* pass. It's the moment when the stack frame size is already final,
* function prologues and epilogues are generated, and the
* machine-dependent code transformations are not done.
*/
PASS_INFO(stackleak_cleanup, "*free_cfg", 1, PASS_POS_INSERT_BEFORE);
if (!plugin_default_version_check(version, &gcc_version)) {
error(G_("incompatible gcc/plugin versions"));
return 1;
}
/* Parse the plugin arguments */
for (i = 0; i < argc; i++) {
if (!strcmp(argv[i].key, "disable"))
return 0;
if (!strcmp(argv[i].key, "track-min-size")) {
if (!argv[i].value) {
error(G_("no value supplied for option '-fplugin-arg-%s-%s'"),
plugin_name, argv[i].key);
return 1;
}
track_frame_size = atoi(argv[i].value);
if (track_frame_size < 0) {
error(G_("invalid option argument '-fplugin-arg-%s-%s=%s'"),
plugin_name, argv[i].key, argv[i].value);
return 1;
}
} else {
error(G_("unknown option '-fplugin-arg-%s-%s'"),
plugin_name, argv[i].key);
return 1;
}
}
/* Give the information about the plugin */
register_callback(plugin_name, PLUGIN_INFO, NULL,
&stackleak_plugin_info);
/* Register to be called before processing a translation unit */
register_callback(plugin_name, PLUGIN_START_UNIT,
&stackleak_start_unit, NULL);
/* Register an extra GCC garbage collector (GGC) root table */
register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS, NULL,
(void *)>_ggc_r_gt_stackleak);
/*
* Hook into the Pass Manager to register new gcc passes.
*
* The stack frame size info is available only at the last RTL pass,
* when it's too late to insert complex code like a function call.
* So we register two gcc passes to instrument every function at first
* and remove the unneeded instrumentation later.
*/
register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
&stackleak_instrument_pass_info);
register_callback(plugin_name, PLUGIN_PASS_MANAGER_SETUP, NULL,
&stackleak_cleanup_pass_info);
return 0;
}
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