diff options
-rw-r--r-- | libc/bionic/heap_tagging.cpp | 3 | ||||
-rw-r--r-- | libc/bionic/libc_init_static.cpp | 135 | ||||
-rw-r--r-- | libc/platform/bionic/mte.h | 7 |
3 files changed, 117 insertions, 28 deletions
diff --git a/libc/bionic/heap_tagging.cpp b/libc/bionic/heap_tagging.cpp index 49b02daf7..4b3d43c21 100644 --- a/libc/bionic/heap_tagging.cpp +++ b/libc/bionic/heap_tagging.cpp @@ -52,6 +52,9 @@ void SetDefaultHeapTaggingLevel() { globals->heap_pointer_tag = (reinterpret_cast<uintptr_t>(POINTER_TAG) << TAG_SHIFT) | (0xffull << CHECK_SHIFT) | (0xffull << UNTAG_SHIFT); }); +#if defined(USE_SCUDO) + scudo_malloc_disable_memory_tagging(); +#endif // USE_SCUDO break; #if defined(USE_SCUDO) case M_HEAP_TAGGING_LEVEL_SYNC: diff --git a/libc/bionic/libc_init_static.cpp b/libc/bionic/libc_init_static.cpp index 3705606f1..2e4ee11a9 100644 --- a/libc/bionic/libc_init_static.cpp +++ b/libc/bionic/libc_init_static.cpp @@ -39,15 +39,17 @@ #include "libc_init_common.h" #include "pthread_internal.h" +#include "platform/bionic/macros.h" +#include "platform/bionic/mte.h" #include "platform/bionic/page.h" +#include "private/KernelArgumentBlock.h" +#include "private/bionic_asm.h" +#include "private/bionic_asm_note.h" #include "private/bionic_call_ifunc_resolver.h" #include "private/bionic_elf_tls.h" #include "private/bionic_globals.h" -#include "platform/bionic/macros.h" -#include "private/bionic_asm.h" -#include "private/bionic_asm_note.h" #include "private/bionic_tls.h" -#include "private/KernelArgumentBlock.h" +#include "sys/system_properties.h" #if __has_feature(hwaddress_sanitizer) #include <sanitizer/hwasan_interface.h> @@ -61,6 +63,7 @@ __LIBC_HIDDEN__ void* __libc_sysinfo; #endif extern "C" int __cxa_atexit(void (*)(void *), void *, void *); +extern "C" const char* __gnu_basename(const char* path); static void call_array(init_func_t** list, int argc, char* argv[], char* envp[]) { // First element is -1, list is null-terminated @@ -160,6 +163,30 @@ static void layout_static_tls(KernelArgumentBlock& args) { layout.finish_layout(); } +// Get the presiding config string, in the following order of priority: +// 1. Environment variables. +// 2. System properties, in the order they're specified in sys_prop_names. +// If neither of these options are specified, this function returns false. +// Otherwise, it returns true, and the presiding options string is written to +// the `options` buffer of size `size`. If this function returns true, `options` +// is guaranteed to be null-terminated. `options_size` should be at least +// PROP_VALUE_MAX. +bool get_config_from_env_or_sysprops(const char* env_var_name, const char* const* sys_prop_names, + size_t sys_prop_names_size, char* options, + size_t options_size) { + const char* env = getenv(env_var_name); + if (env && *env != '\0') { + strncpy(options, env, options_size); + options[options_size - 1] = '\0'; // Ensure null-termination. + return true; + } + + for (size_t i = 0; i < sys_prop_names_size; ++i) { + if (__system_property_get(sys_prop_names[i], options) && *options != '\0') return true; + } + return false; +} + #ifdef __aarch64__ static bool __read_memtag_note(const ElfW(Nhdr)* note, const char* name, const char* desc, unsigned* result) { @@ -204,42 +231,94 @@ static unsigned __get_memtag_note(const ElfW(Phdr)* phdr_start, size_t phdr_ct, return 0; } +// Returns true if there's an environment setting (either sysprop or env var) +// that should overwrite the ELF note, and places the equivalent heap tagging +// level into *level. +static bool get_environment_memtag_setting(HeapTaggingLevel* level) { + static const char kMemtagPrognameSyspropPrefix[] = "arm64.memtag.process."; + + const char* progname = __libc_shared_globals()->init_progname; + if (progname == nullptr) return false; + + const char* basename = __gnu_basename(progname); + + static constexpr size_t kOptionsSize = PROP_VALUE_MAX; + char options_str[kOptionsSize]; + size_t sysprop_size = strlen(basename) + strlen(kMemtagPrognameSyspropPrefix) + 1; + char* sysprop_name = static_cast<char*>(alloca(sysprop_size)); + + async_safe_format_buffer(sysprop_name, sysprop_size, "%s%s", kMemtagPrognameSyspropPrefix, + basename); + + if (!get_config_from_env_or_sysprops("MEMTAG_OPTIONS", &sysprop_name, + /* sys_prop_names_size */ 1, options_str, kOptionsSize)) { + return false; + } + + if (strcmp("sync", options_str) == 0) { + *level = M_HEAP_TAGGING_LEVEL_SYNC; + } else if (strcmp("async", options_str) == 0) { + *level = M_HEAP_TAGGING_LEVEL_ASYNC; + } else if (strcmp("off", options_str) == 0) { + *level = M_HEAP_TAGGING_LEVEL_TBI; + } else { + async_safe_format_log( + ANDROID_LOG_ERROR, "libc", + "unrecognized memtag level: \"%s\" (options are \"sync\", \"async\", or \"off\").", + options_str); + return false; + } + + return true; +} + +// Returns the initial heap tagging level. Note: This function will never return +// M_HEAP_TAGGING_LEVEL_NONE, if MTE isn't enabled for this process we enable +// M_HEAP_TAGGING_LEVEL_TBI. +static HeapTaggingLevel __get_heap_tagging_level(const void* phdr_start, size_t phdr_ct, + uintptr_t load_bias) { + HeapTaggingLevel level; + if (get_environment_memtag_setting(&level)) return level; + + unsigned note_val = + __get_memtag_note(reinterpret_cast<const ElfW(Phdr)*>(phdr_start), phdr_ct, load_bias); + if (note_val & ~(NT_MEMTAG_LEVEL_MASK | NT_MEMTAG_HEAP)) { + async_safe_fatal("unrecognized android.memtag note: desc = %d", note_val); + } + + if (!(note_val & NT_MEMTAG_HEAP)) return M_HEAP_TAGGING_LEVEL_TBI; + + unsigned memtag_level = note_val & NT_MEMTAG_LEVEL_MASK; + switch (memtag_level) { + case NT_MEMTAG_LEVEL_ASYNC: + return M_HEAP_TAGGING_LEVEL_ASYNC; + case NT_MEMTAG_LEVEL_DEFAULT: + case NT_MEMTAG_LEVEL_SYNC: + return M_HEAP_TAGGING_LEVEL_SYNC; + default: + async_safe_fatal("unrecognized android.memtag note: level = %d", memtag_level); + } +} + // Figure out the desired memory tagging mode (sync/async, heap/globals/stack) for this executable. // This function is called from the linker before the main executable is relocated. __attribute__((no_sanitize("hwaddress", "memtag"))) void __libc_init_mte(const void* phdr_start, size_t phdr_ct, uintptr_t load_bias) { - unsigned v = - __get_memtag_note(reinterpret_cast<const ElfW(Phdr)*>(phdr_start), phdr_ct, load_bias); + HeapTaggingLevel level = __get_heap_tagging_level(phdr_start, phdr_ct, load_bias); - if (v & ~(NT_MEMTAG_LEVEL_MASK | NT_MEMTAG_HEAP)) { - async_safe_fatal("unrecognized android.memtag note: desc = %d", v); - } - - if (v & NT_MEMTAG_HEAP) { - unsigned memtag_level = v & NT_MEMTAG_LEVEL_MASK; - unsigned long arg = PR_TAGGED_ADDR_ENABLE | (0xfffe << PR_MTE_TAG_SHIFT); - HeapTaggingLevel level; - switch (memtag_level) { - case NT_MEMTAG_LEVEL_ASYNC: - arg |= PR_MTE_TCF_ASYNC; - level = M_HEAP_TAGGING_LEVEL_ASYNC; - break; - case NT_MEMTAG_LEVEL_DEFAULT: - case NT_MEMTAG_LEVEL_SYNC: - arg |= PR_MTE_TCF_SYNC; - level = M_HEAP_TAGGING_LEVEL_SYNC; - break; - default: - async_safe_fatal("unrecognized android.memtag note: level = %d", memtag_level); - } + if (level == M_HEAP_TAGGING_LEVEL_SYNC || level == M_HEAP_TAGGING_LEVEL_ASYNC) { + unsigned long prctl_arg = PR_TAGGED_ADDR_ENABLE | PR_MTE_TAG_SET_NONZERO; + prctl_arg |= (level == M_HEAP_TAGGING_LEVEL_SYNC) ? PR_MTE_TCF_SYNC : PR_MTE_TCF_ASYNC; - if (prctl(PR_SET_TAGGED_ADDR_CTRL, arg, 0, 0, 0) == 0) { + if (prctl(PR_SET_TAGGED_ADDR_CTRL, prctl_arg, 0, 0, 0) == 0) { __libc_shared_globals()->initial_heap_tagging_level = level; return; } } + // MTE was either not enabled, or wasn't supported on this device. Try and use + // TBI. if (prctl(PR_SET_TAGGED_ADDR_CTRL, PR_TAGGED_ADDR_ENABLE, 0, 0, 0) == 0) { __libc_shared_globals()->initial_heap_tagging_level = M_HEAP_TAGGING_LEVEL_TBI; } diff --git a/libc/platform/bionic/mte.h b/libc/platform/bionic/mte.h index b11b1a678..73cd821b6 100644 --- a/libc/platform/bionic/mte.h +++ b/libc/platform/bionic/mte.h @@ -29,6 +29,13 @@ #pragma once #include <sys/auxv.h> +#include <sys/prctl.h> + +// Note: Most PR_MTE_* constants come from the upstream kernel. This tag mask +// allows for the hardware to provision any nonzero tag. Zero tags are reserved +// for scudo to use for the chunk headers in order to prevent linear heap +// overflow/underflow. +#define PR_MTE_TAG_SET_NONZERO (0xfffeUL << PR_MTE_TAG_SHIFT) inline bool mte_supported() { #if defined(__aarch64__) |