152 lines
4.6 KiB
Diff
152 lines
4.6 KiB
Diff
From ffff09335760efc655faf093b6fbb364cfae4ad7 Mon Sep 17 00:00:00 2001
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From: Jan Janssen <medhefgo@web.de>
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Date: Sat, 7 Jan 2023 22:16:52 +0100
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Subject: [PATCH] boot: Simplify object erasure
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This erase_obj() machinery looks like voodoo and creates an awful lot of
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noise as soon as we get back to building with -O0. We can do this in a
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more simple way by introducing a struct that holds the information we
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need on cleanup. When building with optimization enabled, all this gets
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inlined and the eraser vanishes.
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(cherry picked from commit 3f92dc2fd4070b213e6bc85263a9bef06ec9a486)
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Related: RHEL-16182
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---
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src/basic/memory-util.c | 18 ----------
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src/basic/memory-util.h | 12 +------
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src/boot/efi/random-seed.c | 1 +
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src/fundamental/memory-util-fundamental.h | 42 +++++++++++++++++++++++
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src/fundamental/meson.build | 1 +
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5 files changed, 45 insertions(+), 29 deletions(-)
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create mode 100644 src/fundamental/memory-util-fundamental.h
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diff --git a/src/basic/memory-util.c b/src/basic/memory-util.c
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index 2983762117..c4f54c7b4e 100644
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--- a/src/basic/memory-util.c
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+++ b/src/basic/memory-util.c
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@@ -38,21 +38,3 @@ bool memeqbyte(uint8_t byte, const void *data, size_t length) {
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/* Now we know first 16 bytes match, memcmp() with self. */
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return memcmp(data, p + 16, length) == 0;
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}
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-
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-#if !HAVE_EXPLICIT_BZERO
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-/*
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- * The pointer to memset() is volatile so that compiler must de-reference the pointer and can't assume that
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- * it points to any function in particular (such as memset(), which it then might further "optimize"). This
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- * approach is inspired by openssl's crypto/mem_clr.c.
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- */
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-typedef void *(*memset_t)(void *,int,size_t);
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-
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-static volatile memset_t memset_func = memset;
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-
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-void* explicit_bzero_safe(void *p, size_t l) {
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- if (l > 0)
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- memset_func(p, '\0', l);
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-
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- return p;
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-}
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-#endif
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diff --git a/src/basic/memory-util.h b/src/basic/memory-util.h
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index eea9c0e92f..d26a0918e1 100644
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--- a/src/basic/memory-util.h
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+++ b/src/basic/memory-util.h
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@@ -9,6 +9,7 @@
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#include "alloc-util.h"
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#include "macro.h"
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+#include "memory-util-fundamental.h"
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size_t page_size(void) _pure_;
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#define PAGE_ALIGN(l) ALIGN_TO((l), page_size())
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@@ -91,17 +92,6 @@ static inline void *mempmem_safe(const void *haystack, size_t haystacklen, const
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return (uint8_t*) p + needlelen;
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}
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-#if HAVE_EXPLICIT_BZERO
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-static inline void* explicit_bzero_safe(void *p, size_t l) {
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- if (l > 0)
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- explicit_bzero(p, l);
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-
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- return p;
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-}
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-#else
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-void *explicit_bzero_safe(void *p, size_t l);
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-#endif
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-
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static inline void* erase_and_free(void *p) {
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size_t l;
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diff --git a/src/boot/efi/random-seed.c b/src/boot/efi/random-seed.c
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index aea4f7e532..3c9df5bb54 100644
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--- a/src/boot/efi/random-seed.c
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+++ b/src/boot/efi/random-seed.c
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@@ -3,6 +3,7 @@
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#include <efi.h>
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#include <efilib.h>
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+#include "memory-util-fundamental.h"
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#include "missing_efi.h"
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#include "random-seed.h"
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#include "secure-boot.h"
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diff --git a/src/fundamental/memory-util-fundamental.h b/src/fundamental/memory-util-fundamental.h
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new file mode 100644
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index 0000000000..9015300ae8
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--- /dev/null
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+++ b/src/fundamental/memory-util-fundamental.h
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@@ -0,0 +1,42 @@
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+/* SPDX-License-Identifier: LGPL-2.1-or-later */
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+#pragma once
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+
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+#include <stddef.h>
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+
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+#ifdef SD_BOOT
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+# include "efi-string.h"
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+#else
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+# include <string.h>
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+#endif
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+
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+#include "macro-fundamental.h"
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+
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+#if defined(HAVE_EXPLICIT_BZERO)
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+static inline void *explicit_bzero_safe(void *p, size_t l) {
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+ if (p && l > 0)
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+ explicit_bzero(p, l);
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+
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+ return p;
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+}
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+#else
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+static inline void *explicit_bzero_safe(void *p, size_t l) {
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+ if (p && l > 0) {
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+ memset(p, 0, l);
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+ __asm__ __volatile__("" : : "r"(p) : "memory");
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+ }
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+ return p;
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+}
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+#endif
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+
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+struct VarEraser {
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+ void *p;
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+ size_t size;
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+};
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+
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+static inline void erase_var(struct VarEraser *e) {
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+ explicit_bzero_safe(e->p, e->size);
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+}
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+
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+/* Mark var to be erased when leaving scope. */
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+#define CLEANUP_ERASE(var) \
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+ _cleanup_(erase_var) _unused_ struct VarEraser CONCATENATE(_eraser_, UNIQ) = { .p = &var, .size = sizeof(var) }
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diff --git a/src/fundamental/meson.build b/src/fundamental/meson.build
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index 3810d6b456..4b8e32337d 100644
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--- a/src/fundamental/meson.build
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+++ b/src/fundamental/meson.build
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@@ -6,6 +6,7 @@ fundamental_headers = files(
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'bootspec-fundamental.h',
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'efivars-fundamental.h',
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'macro-fundamental.h',
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+ 'memory-util-fundamental.h',
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'sha256.h',
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'string-util-fundamental.h',
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'tpm-pcr.h',
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