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Message-Id: <A19A4EED-F081-47A3-831F-3A7E5F5173C3@cognitive-electronics.com>
Date: Mon, 3 Nov 2014 09:06:10 -0500
From: Richard Gorton <rcgorton@...nitive-electronics.com>
To: "musl@...ts.openwall.com" <musl@...ts.openwall.com>
Subject: small patches for src/env
Attached is a small patch, mostly comments for a couple of files in src/env
Regards,
Richard
rcgorton@...-e.com
Index: __init_tls.c
===================================================================
--- __init_tls.c (revision 47)
+++ __init_tls.c (working copy)
@@ -22,7 +22,8 @@
#ifndef SHARED
-static long long builtin_tls[(sizeof(struct pthread) + 64)/sizeof(long long)];
+#define SMALL_NUM_TLS_VARS 16
+static long long builtin_tls[(sizeof(struct pthread) + (sizeof(uintptr_t) * SMALL_NUM_TLS_VARS))/sizeof(long long)];
struct tls_image {
void *image;
@@ -60,6 +61,10 @@
typedef Elf64_Phdr Phdr;
#endif
+/*
+ * See ELF Handling for Thread-Local Storage:
+ * http://www.akkadia.org/drepper/tls.pdf
+ */
void __init_tls(size_t *aux)
{
unsigned char *p;
Index: __stack_chk_fail.c
===================================================================
--- __stack_chk_fail.c (revision 47)
+++ __stack_chk_fail.c (working copy)
@@ -4,6 +4,12 @@
uintptr_t __stack_chk_guard;
+/*
+ * The objective is to have some additional entropy for the canary.
+ * The value (1103515245) is an LCG: Linear Congruential Generator
+ * http://en.wikipedia.org/wiki/Linear_congruential_generator
+ * and matches the value used elsewhere in musl (src/prng) for pseudo-random number generation
+ */
void __init_ssp(void *entropy)
{
if (entropy) memcpy(&__stack_chk_guard, entropy, sizeof(uintptr_t));
Index: __libc_start_main.c
===================================================================
--- __libc_start_main.c (revision 47)
+++ __libc_start_main.c (working copy)
@@ -23,6 +23,16 @@
extern size_t __hwcap, __sysinfo;
extern char *__progname, *__progname_full;
+/*
+ * The initial process stack for ELF executables is described in the System V Application Binary Interface
+ * Architecture processor supplement, such as the one for AMD64 == x86_64:
+ * http://refspecs.linux-foundation.org/elf/x86_64-abi-0.95.pdf
+ * Search for "Initial Process Stack"
+ *
+ * Basically, the order of content is:
+ * argc, argv[] (null terminated), envp[] (null terminated), auxv (null terminated)
+ *
+ */
#ifndef SHARED
static
#endif
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