Kernel+LibELF: Expose ELF Auxiliary Vector to Userspace

The AT_* entries are placed after the environment variables, so that
they can be found by iterating until the end of the envp array, and then
going even further beyond :^)

Libraries/LibELF/AuxiliaryVector.h

@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2020, The SerenityOS developers.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this
+ *    list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+/* Auxiliary Vector types, from Intel386 ABI ver 1.0 section 2.3.3 */
+typedef struct
+{
+    long a_type; /* Note: Extended to long from int, for ease of comaptibility w/64 bit */
+    union {
+        long a_val;
+        void* a_ptr;
+        void (*a_fnc)(); /* In spec, not used */
+    } a_un;
+} auxv_t;
+
+#define AT_NULL 0           /* No length, last entry's a_type has this value */
+#define AT_IGNORE 1         /* Entry has no meaning, a_un undefined */
+#define AT_EXECFD 2         /* a_val contains a file descriptor of the main program image */
+#define AT_PHDR 3           /* a_ptr contains pointer to program header table of main program image */
+#define AT_PHENT 4          /* a_val holds size of program header table entries */
+#define AT_PHNUM 5          /* a_val holds number of program header table entries */
+#define AT_PAGESZ 6         /* a_val gives system page size in bytes */
+#define AT_BASE 7           /* a_ptr holds base address that Loader was loaded into memory */
+#define AT_FLAGS 8          /* a_val holds 1 bit flags. Undefined flags are 0 */
+#define AT_ENTRY 9          /* a_ptr holds entry point of application for loader */
+#define AT_NOTELF 10        /* a_val non-zero if the program is not ELF */
+#define AT_UID 11           /* a_val holds real user id of process */
+#define AT_EUID 12          /* a_val holds effective user id of process */
+#define AT_GID 13           /* a_val holds real group id of process */
+#define AT_EGID 14          /* a_val holds effective group id of process */
+#define AT_PLATFORM 15      /* a_val points to a string containing platform name */
+#define AT_HWCAP 16         /* a_val contains bitmask of CPU features. Equivalent to CPUID 1.EDX*/
+#define AT_CLKTCK 17        /* a_val contains frequence at which times() increments. (Re: Spec. What is times()?) */
+#define AT_SECURE 23        /* a_val holds 1 if program in secure mode (e.g. suid). Otherwise 0 */
+#define AT_BASE_PLATFORM 24 /* a_ptr points to a string identifying base platform name, which might be different from platform (e.g x86_64 when in i386 compat)  */
+#define AT_RANDOM 25        /* a_ptr points to 16 securely generated random bytes */
+#define AT_HWCAP2 26        /* a_val holds extended hw feature mask. Currently 0 */
+#define AT_EXECFN 31        /* a_ptr points to file name of executed program */
+
+#ifdef __cplusplus
+#    include <AK/String.h>
+#    include <AK/Types.h>
+
+struct AuxiliaryValue {
+    enum Type {
+        Null = AT_NULL,
+        Ignore = AT_IGNORE,
+        ExecFileDescriptor = AT_EXECFD,
+        Phdr = AT_PHDR,
+        Phent = AT_PHENT,
+        Phnum = AT_PHNUM,
+        PageSize = AT_PAGESZ,
+        BaseAddress = AT_BASE,
+        Flags = AT_FLAGS,
+        Entry = AT_ENTRY,
+        NotELF = AT_NOTELF,
+        Uid = AT_UID,
+        EUid = AT_EUID,
+        Gid = AT_GID,
+        EGid = AT_EGID,
+        Platform = AT_PLATFORM,
+        HwCap = AT_HWCAP,
+        ClockTick = AT_CLKTCK,
+        Secure = AT_SECURE,
+        BasePlatform = AT_BASE_PLATFORM,
+        Random = AT_RANDOM,
+        HwCap2 = AT_HWCAP2,
+        ExecFilename = AT_EXECFN
+    };
+
+    AuxiliaryValue(Type type, long val)
+    {
+        auxv.a_type = type;
+        auxv.a_un.a_val = val;
+    }
+    AuxiliaryValue(Type type, void* ptr)
+    {
+        auxv.a_type = type;
+        auxv.a_un.a_ptr = (void*)ptr;
+    }
+    AuxiliaryValue(Type type, String string)
+    {
+        auxv.a_type = type;
+        auxv.a_un.a_ptr = nullptr;
+        optional_string = string;
+    }
+
+    auxv_t auxv {};
+    String optional_string;
+};
+
+#endif /* __cplusplus */