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commit 533bb7c2ae156ff2d49b2e0b20b33810ba5e2721
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Author: Siddhesh Poyarekar <siddhesh@redhat.com>
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Date: Wed Nov 12 19:30:24 2014 +0530
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Fix stack alignment when loader is invoked directly
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The s390 ABI requires the stack pointer to be aligned at 8-bytes.
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When a program is invoked as an argument to the dynamic linker,
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_dl_start_user adjusts the stack to remove the dynamic linker
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arguments so that the program sees only its name and arguments. This
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may result in the stack being misaligned since each argument shift is
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only a word and not a double-word.
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This is now fixed shifting argv and envp down instead of shifting argc
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up and reclaiming the stack. This requires _dl_argv to be adjusted
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and hence, is no longer relro.
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diff --git glibc-2.17-c758a686/sysdeps/s390/s390-32/dl-machine.h glibc-2.17-c758a686/sysdeps/s390/s390-32/dl-machine.h
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index c56185c..79f8ef9 100644
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--- glibc-2.17-c758a686/sysdeps/s390/s390-32/dl-machine.h
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+++ glibc-2.17-c758a686/sysdeps/s390/s390-32/dl-machine.h
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@@ -166,18 +166,49 @@ _dl_start_user:\n\
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# See if we were run as a command with the executable file\n\
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# name as an extra leading argument.\n\
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l %r1,_dl_skip_args@GOT12(0,%r12)\n\
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- l %r1,0(%r1) # load _dl_skip_args\n\
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+ l %r1,0(%r1) # load _dl_skip_args\n\
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+ ltr %r1,%r1\n\
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+ je .L4 # Skip the arg adjustment if there were none.\n\
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# Get the original argument count.\n\
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l %r0,96(%r15)\n\
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# Subtract _dl_skip_args from it.\n\
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sr %r0,%r1\n\
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- # Adjust the stack pointer to skip _dl_skip_args words.\n\
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- sll %r1,2\n\
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- ar %r15,%r1\n\
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- # Set the back chain to zero again\n\
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- xc 0(4,%r15),0(%r15)\n\
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# Store back the modified argument count.\n\
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st %r0,96(%r15)\n\
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+ # Copy argv and envp forward to account for skipped argv entries.\n\
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+ # We skipped at least one argument or we would not get here.\n\
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+ la %r6,100(%r15) # Destination pointer i.e. &argv[0]\n\
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+ lr %r5,%r6\n\
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+ lr %r0,%r1\n\
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+ sll %r0,2\n # Number of skipped bytes.\n\
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+ ar %r5,%r0 # Source pointer = Dest + Skipped args.\n\
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+ # argv copy loop:\n\
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+.L1: l %r7,0(%r5) # Load a word from the source.\n\
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+ st %r7,0(%r6) # Store the word in the destination.\n\
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+ ahi %r5,4\n\
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+ ahi %r6,4\n\
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+ ltr %r7,%r7\n\
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+ jne .L1 # Stop after copying the NULL.\n\
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+ # envp copy loop:\n\
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+.L2: l %r7,0(%r5) # Load a word from the source.\n\
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+ st %r7,0(%r6) # Store the word in the destination.\n\
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+ ahi %r5,4\n\
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+ ahi %r6,4\n\
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+ ltr %r7,%r7\n\
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+ jne .L2 # Stop after copying the NULL.\n\
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+ # Now we have to zero out the envp entries after NULL to allow\n\
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+ # start.S to properly find auxv by skipping zeroes.\n\
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+ # zero out loop:\n\
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+ lhi %r7,0\n\
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+.L3: st %r7,0(%r6) # Store zero.\n\
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+ ahi %r6,4 # Advance dest pointer.\n\
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+ ahi %r1,-1 # Subtract one from the word count.\n\
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+ ltr %r1,%r1\n\
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+ jne .L3 # Keep copying if the word count is non-zero.\n\
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+ # Adjust _dl_argv\n\
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+ la %r6,100(%r15)\n\
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+ l %r1,_dl_argv@GOT12(0,%r12)\n\
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+ st %r6,0(%r1)\n\
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# The special initializer gets called with the stack just\n\
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# as the application's entry point will see it; it can\n\
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# switch stacks if it moves these contents over.\n\
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@@ -185,7 +216,7 @@ _dl_start_user:\n\
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# Call the function to run the initializers.\n\
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# Load the parameters:\n\
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# (%r2, %r3, %r4, %r5) = (_dl_loaded, argc, argv, envp)\n\
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- l %r2,_rtld_local@GOT(%r12)\n\
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+.L4: l %r2,_rtld_local@GOT(%r12)\n\
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l %r2,0(%r2)\n\
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l %r3,96(%r15)\n\
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la %r4,100(%r15)\n\
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@@ -198,6 +229,9 @@ _dl_start_user:\n\
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l %r14,_dl_fini@GOT(%r12)\n\
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# Free stack frame\n\
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ahi %r15,96\n\
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+ # Reload argc and argv for the user's entry point.\n\
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+ # l %r2,0(%r15)\n\
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+ # la %r3,4(%r15)\n\
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# Jump to the user's entry point (saved in %r8).\n\
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br %r8\n\
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.Llit:\n\
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diff --git glibc-2.17-c758a686/sysdeps/s390/s390-32/dl-sysdep.h glibc-2.17-c758a686/sysdeps/s390/s390-32/dl-sysdep.h
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new file mode 100644
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index 0000000..b992778
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--- /dev/null
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+++ glibc-2.17-c758a686/sysdeps/s390/s390-32/dl-sysdep.h
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@@ -0,0 +1,23 @@
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+/* System-specific settings for dynamic linker code. S/390 version.
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+ Copyright (C) 2014 Free Software Foundation, Inc.
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+ This file is part of the GNU C Library.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library. If not, see
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+ <http://www.gnu.org/licenses/>. */
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+
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+#include_next <dl-sysdep.h>
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+
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+/* _dl_argv cannot be attribute_relro, because _dl_start_user
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+ might write into it after _dl_start returns. */
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+#define DL_ARGV_NOT_RELRO 1
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