Add writeups/unaligned-mem

5 files changed, 184 insertions, 0 deletions

diff --git a/writeups/unaligned-mem/.gitignore b/writeups/unaligned-mem/.gitignore
new file mode 100644
index 0000000..5c3dfdd
--- /dev/null
+++ b/writeups/unaligned-mem/.gitignore
@@ -0,0 +1,3 @@
+/unamem
+/unamem-*
+/*.core
diff --git a/writeups/unaligned-mem/Makefile b/writeups/unaligned-mem/Makefile
new file mode 100644
index 0000000..175b46b
--- /dev/null
+++ b/writeups/unaligned-mem/Makefile
@@ -0,0 +1,55 @@
+CC ?= cc
+CC_FLAGS = -g -O0 -Wall -Wextra
+CC_CMD = $(CC) $(CC_FLAGS) $(CC_EXTRA_CLAGS)
+OBJ = \
+	unamem \
+	unamem-armv4t \
+	unamem-armv7 \
+	unamem-aarch64 \
+	unamem-arc \
+	unamem-arceb \
+	unamem-i686 \
+	unamem-x86_64 \
+	unamem-m68k \
+	unamem-mips \
+	unamem-mpsl \
+	unamem-ppc \
+	unamem-sh4
+
+.PHONY: clean test
+
+all: $(OBJ) test
+
+clean:
+	rm -f $(OBJ)
+
+
+unamem: unamem.c
+	$(CC_CMD) -o unamem unamem.c
+unamem-armv4t: unamem.c
+	xcomp linux-app armv4t arm-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-armv4t unamem.c
+unamem-armv7: unamem.c
+	xcomp linux-app armv7 arm-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-armv7 unamem.c
+unamem-aarch64: unamem.c
+	xcomp linux-app aarch64 aarch64-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-aarch64 unamem.c
+unamem-arc: unamem.c
+	xcomp linux-app arc arc-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-arc unamem.c
+unamem-arceb: unamem.c
+	xcomp linux-app arceb arceb-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-arceb unamem.c
+unamem-i686: unamem.c
+	xcomp linux-app i686 i686-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-i686 unamem.c
+unamem-x86_64: unamem.c
+	xcomp linux-app x86_64 x86_64-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-x86_64 unamem.c
+unamem-m68k: unamem.c
+	xcomp linux-app m68k m68k-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-m68k unamem.c
+unamem-mips: unamem.c
+	xcomp linux-app mips mips-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-mips unamem.c
+unamem-mpsl: unamem.c
+	xcomp linux-app mpsl mipsel-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-mpsl unamem.c
+unamem-ppc: unamem.c
+	xcomp linux-app ppc powerpc-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-ppc unamem.c
+unamem-sh4: unamem.c
+	xcomp linux-app sh4 sh4-linux-cc $(CC_FLAGS) $(CC_EXTRA_CLAGS) -static -o unamem-sh4 unamem.c
+
+test: run-all $(OBJ)
+	./run-all
diff --git a/writeups/unaligned-mem/run-all b/writeups/unaligned-mem/run-all
new file mode 100755
index 0000000..85360c7
--- /dev/null
+++ b/writeups/unaligned-mem/run-all
@@ -0,0 +1,8 @@
+#!/bin/bash
+ulimit -c 0
+
+for prog in unamem-*
+do
+	echo "==================== $prog ===================="
+	./"$prog"
+done
diff --git a/writeups/unaligned-mem/unaligned-mem.md b/writeups/unaligned-mem/unaligned-mem.md
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/writeups/unaligned-mem/unaligned-mem.md
diff --git a/writeups/unaligned-mem/unamem.c b/writeups/unaligned-mem/unamem.c
new file mode 100644
index 0000000..cadfba1
--- /dev/null
+++ b/writeups/unaligned-mem/unamem.c
@@ -0,0 +1,118 @@
+#define _POSIX_C_SOURCE 200112L
+#include <stdio.h>
+#include <stdint.h>
+#include <limits.h>
+#include <error.h>
+#include <assert.h>
+
+#include <unistd.h>
+#include <wait.h>
+
+#define ARGV0 "unamem"
+#define DONT_FORK 1
+
+
+static void report_wait (const int status) {
+	if (WIFEXITED(status)) {
+		printf("exit %d\n", WEXITSTATUS(status));
+	}
+	else if (WIFSIGNALED(status)) {
+		printf("signal %d\n", WTERMSIG(status));
+	}
+	else {
+		printf("?\n");
+	}
+}
+
+int main (void) {
+	static char m[9]; // bss address is nicer than stack
+	char *c;
+	uintptr_t *p;
+	pid_t pid;
+	int status;
+
+	printf(
+		"CHAR_BIT:  %d\n"
+		"word:      %zd\n"
+		"uintptr_t: %zd\n"
+		"size_t:    %zd\n"
+		"short:     %zd\n"
+		"int:       %zd\n"
+		"long:      %zd\n"
+		"long long: %zd\n"
+		,
+		CHAR_BIT,
+		CHAR_BIT * sizeof(uintptr_t),
+		sizeof(uintptr_t),
+		sizeof(size_t),
+		sizeof(short),
+		sizeof(int),
+		sizeof(long),
+		sizeof(long long));
+
+	c = m;
+	p = (void*)(m + 1);
+
+	printf(
+		"malloc:    %zx", (uintptr_t)m);
+	for (size_t i = sizeof(uintptr_t); i > 1; i /= 2) {
+		if ((uintptr_t)m % i == 0) {
+			printf(" {%zu}", i);
+		}
+	}
+	printf("\n");
+
+	printf(
+		"c:         %zx\n"
+		"p:         %zx\n"
+		,
+		(uintptr_t)c,
+		(uintptr_t)p);
+
+	pid = DONT_FORK ? 0 : fork();
+	if (pid > 0) {
+		printf(
+		"access:    "
+		);
+		wait(&status);
+		report_wait(status);
+	}
+	else if (pid == 0) {
+		*p = UINTPTR_MAX;
+		*c = 0;
+		assert(*p == UINTPTR_MAX);
+		assert(*c == 0);
+
+		*c = 0;
+		*p = UINTPTR_MAX;
+		assert(*p == UINTPTR_MAX);
+		assert(*c == 0);
+	}
+	else {
+		perror(ARGV0": fork()");
+		return 1;
+	}
+
+	pid = DONT_FORK ? 0 : fork();
+	if (pid > 0) {
+		printf(
+		"float:     "
+		);
+		wait(&status);
+		report_wait(status);
+	}
+	else if (pid == 0) {
+		volatile float a, b, c;
+
+		a = 0.1;
+		b = 1.0;
+		c = b / a;
+		assert(c > 1.0);
+	}
+	else {
+		perror(ARGV0": fork()");
+		return 1;
+	}
+
+	return 0;
+}