On MacOS X 10.10, when postprocessing tool executables, set the SVMA
of __PAGEZERO to zero. Without this, the 10.10 kernel refuses to
start these executables. Based on investigations and a
proof-of-concept implementation by Rhys Kidd (rhyskidd@gmail.com).
Part of bug 339045.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@14697 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/coregrind/Makefile.am b/coregrind/Makefile.am
index 7fb2618..81245e2 100644
--- a/coregrind/Makefile.am
+++ b/coregrind/Makefile.am
@@ -642,7 +642,7 @@
BUILT_SOURCES += fixup_macho_loadcmds
fixup_macho_loadcmds: fixup_macho_loadcmds.c
- $(CC) -g -Wall -o $@ $<
+ $(CC) -I $(top_srcdir) -g -Wall -o $@ $<
CLEANFILES += fixup_macho_loadcmds
diff --git a/coregrind/fixup_macho_loadcmds.c b/coregrind/fixup_macho_loadcmds.c
index 77524f8..d66ad20 100644
--- a/coregrind/fixup_macho_loadcmds.c
+++ b/coregrind/fixup_macho_loadcmds.c
@@ -6,9 +6,17 @@
*/
/* What does this program do? In short it postprocesses tool
- executables on MacOSX, after linking using /usr/bin/ld. This is so
- as to work around a bug in the linker on Xcode 4.0.0 and Xcode
- 4.0.1. Xcode versions prior to 4.0.0 are unaffected.
+ executables on MacOSX, after linking using /usr/bin/ld.
+
+ This is to deal with two separate and entirely unrelated problems.
+ Problem (1) is a bug in the linker in Xcode 4.0.0. Problem (2) is
+ much newer and concerns linking 64-bit tool executables for
+ Yosemite (10.10).
+
+ --- Problem (1) ------------------------------------------------
+
+ This is a bug in the linker on Xcode 4.0.0 and Xcode 4.0.1. Xcode
+ versions prior to 4.0.0 are unaffected.
The tracking bug is https://bugs.kde.org/show_bug.cgi?id=267997
@@ -70,6 +78,16 @@
information that would have been in the missing __UNIXSTACK entry.
I tried this by hand (with a binary editor) earlier and got
something that worked.
+
+ --- Problem (2) ------------------------------------------------
+
+ On MacOSX 10.10 (Yosemite), the kernel requires all valid
+ executables to have a __PAGEZERO section with SVMA of zero and size
+ of at least one page. However, our tool executables have a
+ __PAGEZERO section with SVMA set to the requested Valgrind load
+ address (typically 0x1'3800'0000). And the kernel won't start
+ those. So we take the opportunity to "fix" this by setting the
+ SVMA to zero. Seems to work and have no obvious bad side effects.
*/
#define DEBUGPRINTING 0
@@ -83,7 +101,6 @@
#include <unistd.h>
#include <fcntl.h>
-
#undef PLAT_x86_darwin
#undef PLAT_amd64_darwin
@@ -100,6 +117,14 @@
#include <mach-o/fat.h>
#include <mach/i386/thread_status.h>
+/* Get hold of DARWIN_VERS, and check it has a sane value. */
+#include "config.h"
+#if DARWIN_VERS != DARWIN_10_5 && DARWIN_VERS != DARWIN_10_6 \
+ && DARWIN_VERS != DARWIN_10_7 && DARWIN_VERS != DARWIN_10_8 \
+ && DARWIN_VERS != DARWIN_10_9 && DARWIN_VERS != DARWIN_10_10
+# error "Unknown DARWIN_VERS value. This file only compiles on Darwin."
+#endif
+
typedef unsigned char UChar;
typedef signed char Char;
@@ -375,6 +400,7 @@
Bool have_rsp = False;
struct segment_command_64* seg__unixstack = NULL;
struct segment_command_64* seg__linkedit = NULL;
+ struct segment_command_64* seg__pagezero = NULL;
/* Loop over the load commands and fill in the above 4 variables. */
@@ -413,6 +439,7 @@
printf("LC_UNIXTHREAD");
break;
default:
+ if (DEBUGPRINTING)
printf("???");
fail("unexpected load command in Mach header");
break;
@@ -450,6 +477,8 @@
seg__linkedit = seg;
if (0 == strcmp(seg->segname, "__UNIXSTACK"))
seg__unixstack = seg;
+ if (0 == strcmp(seg->segname, "__PAGEZERO"))
+ seg__pagezero = seg;
}
}
@@ -495,7 +524,7 @@
/* looks ok */
fprintf(stderr, "fixup_macho_loadcmds: "
"acceptable __UNIXSTACK present; no modifications.\n" );
- goto out;
+ goto maybe_mash_pagezero;
}
if (seg__linkedit) {
@@ -516,7 +545,7 @@
seg->maxprot = 7;
seg->initprot = 3;
/* success */
- goto out;
+ goto maybe_mash_pagezero;
}
/* out of options */
@@ -524,7 +553,20 @@
"out of options.");
/* NOTREACHED */
- out:
+ maybe_mash_pagezero:
+ /* Deal with Problem (2) as documented above. */
+# if DARWIN_VERS == DARWIN_10_10
+ assert(size == 64);
+ if (!seg__pagezero) {
+ fail("Can't find __PAGEZERO to modify; can't continue.");
+ }
+ fprintf(stderr, "fixup_macho_loadcmds: "
+ "changing __PAGEZERO.vmaddr from %p to 0x0.\n",
+ (void*)seg__pagezero->vmaddr);
+ seg__pagezero->vmaddr = 0;
+# endif
+
+ out:
if (ii.img)
unmap_image(&ii);
}
