diff mbox series

[2/2] libgcc: Make heap trampoline support dynamic [PR113403].

Message ID 20240128140733.94198-3-iain@sandoe.co.uk
State New
Headers show
Series libgcc: Make heap trampoline support dynamic [PR113403]. | expand

Commit Message

Iain Sandoe Jan. 28, 2024, 2:07 p.m. UTC 
In order to handle system security constraints during GCC build
and test and that most platform versions cannot link to libgcc_eh
since the unwinder there is incompatible with the system one.

1. We make the support functions weak definitions.
2. We include them as a CRT for platform conditions that do not
   allow libgcc_eh.
3. We ensure that the weak symbols are exported from DSOs (which
   includes exes on Darwin) so that the dynamic linker will
   pick one instance (which avoids duplication of trampoline
   caches).

	PR libgcc/113403

gcc/ChangeLog:

	* config/darwin.h (DARWIN_SHARED_WEAK_ADDS, DARWIN_WEAK_CRTS): New.
	(REAL_LIBGCC_SPEC): Move weak CRT handling to separate spec.
	* config/i386/darwin.h (DARWIN_HEAP_T_LIB): New.
	* config/i386/darwin32-biarch.h (DARWIN_HEAP_T_LIB): New.
	* config/i386/darwin64-biarch.h (DARWIN_HEAP_T_LIB): New.
	* config/rs6000/darwin.h (DARWIN_HEAP_T_LIB): New.

libgcc/ChangeLog:

	* config.host: Build libheap_t.a for i686/x86_64 Darwin.
	* config/aarch64/heap-trampoline.c (HEAP_T_ATTR): New.
	(allocate_tramp_ctrl): Allow a target to build this as a weak def.
	(__gcc_nested_func_ptr_created): Likewise.
	* config/i386/heap-trampoline.c (HEAP_T_ATTR): New.
	(allocate_tramp_ctrl): Allow a target to build this as a weak def.
	(__gcc_nested_func_ptr_created): Likewise.
	* config/t-darwin: Build libheap_t.a (a CRT with heap trampoline
	support).
---
 gcc/config/darwin.h                     | 43 ++++++++++++++++---------
 gcc/config/i386/darwin.h                |  2 ++
 gcc/config/i386/darwin32-biarch.h       |  3 ++
 gcc/config/i386/darwin64-biarch.h       |  3 ++
 gcc/config/rs6000/darwin.h              |  3 ++
 libgcc/config.host                      |  7 ++--
 libgcc/config/aarch64/heap-trampoline.c |  8 +++++
 libgcc/config/i386/heap-trampoline.c    |  8 +++++
 libgcc/config/t-darwin                  | 13 ++++++++
 9 files changed, 72 insertions(+), 18 deletions(-)

Comments

Jakub Jelinek Jan. 28, 2024, 4:32 p.m. UTC | #1 
On Sun, Jan 28, 2024 at 02:07:33PM +0000, Iain Sandoe wrote:
> In order to handle system security constraints during GCC build
> and test and that most platform versions cannot link to libgcc_eh
> since the unwinder there is incompatible with the system one.
> 
> 1. We make the support functions weak definitions.
> 2. We include them as a CRT for platform conditions that do not
>    allow libgcc_eh.
> 3. We ensure that the weak symbols are exported from DSOs (which
>    includes exes on Darwin) so that the dynamic linker will
>    pick one instance (which avoids duplication of trampoline
>    caches).
> 
> 	PR libgcc/113403
> 
> gcc/ChangeLog:
> 
> 	* config/darwin.h (DARWIN_SHARED_WEAK_ADDS, DARWIN_WEAK_CRTS): New.
> 	(REAL_LIBGCC_SPEC): Move weak CRT handling to separate spec.
> 	* config/i386/darwin.h (DARWIN_HEAP_T_LIB): New.
> 	* config/i386/darwin32-biarch.h (DARWIN_HEAP_T_LIB): New.
> 	* config/i386/darwin64-biarch.h (DARWIN_HEAP_T_LIB): New.
> 	* config/rs6000/darwin.h (DARWIN_HEAP_T_LIB): New.
> 
> libgcc/ChangeLog:
> 
> 	* config.host: Build libheap_t.a for i686/x86_64 Darwin.
> 	* config/aarch64/heap-trampoline.c (HEAP_T_ATTR): New.
> 	(allocate_tramp_ctrl): Allow a target to build this as a weak def.
> 	(__gcc_nested_func_ptr_created): Likewise.
> 	* config/i386/heap-trampoline.c (HEAP_T_ATTR): New.
> 	(allocate_tramp_ctrl): Allow a target to build this as a weak def.
> 	(__gcc_nested_func_ptr_created): Likewise.
> 	* config/t-darwin: Build libheap_t.a (a CRT with heap trampoline
> 	support).

The non-darwin parts here (config.host, heap-trampoline.c) here are ok,
I don't know anything about Darwin to judge the rest and you're the
maintainer...

	Jakub
diff mbox series

Patch

diff --git a/gcc/config/darwin.h b/gcc/config/darwin.h
index cb96d67b3b1..31019a0c49d 100644
--- a/gcc/config/darwin.h
+++ b/gcc/config/darwin.h
@@ -314,13 +314,17 @@  extern GTY(()) int darwin_ms_struct;
 # define DARWIN_RPATH_LINK \
 "%{!r:%{!nostdlib:%{!nodefaultrpaths:%(darwin_rpaths)}}}"
 # define DARWIN_SHARED_LIBGCC "-lgcc_s.1.1"
+# define DARWIN_SHARED_WEAK_ADDS " "
 #else
 # define DARWIN_RPATH_LINK ""
 # define DARWIN_SHARED_LIBGCC \
-"%:version-compare(!> 10.11 mmacosx-version-min= -lgcc_s.1.1) \
- %:version-compare(>= 10.11 mmacosx-version-min= -lemutls_w) "
+"%:version-compare(!> 10.11 mmacosx-version-min= -lgcc_s.1.1)"
+# define DARWIN_SHARED_WEAK_ADDS \
+"%{%:version-compare(>= 10.11 mmacosx-version-min= -lemutls_w): \
+ " DARWIN_HEAP_T_LIB "}"
 #endif
 
+
 /* We might elect to add a path even when this compiler does not use embedded
    run paths, so that we can use libraries from an alternate compiler that is
    using embedded runpaths.  */
@@ -398,7 +402,9 @@  extern GTY(()) int darwin_ms_struct;
     %{e*} %{r} \
     %{o*}%{!o:-o a.out} \
     %{!r:%{!nostdlib:%{!nostartfiles:%S}}} \
-    %{L*} %(link_libgcc) %o \
+    %{L*} %(link_libgcc) \
+    %{!r:%{!nostdlib:%{!nodefaultlibs: " DARWIN_WEAK_CRTS "}}} \
+    %o \
     %{!r:%{!nostdlib:%{!nodefaultlibs:\
       %{fprofile-arcs|fprofile-generate*|coverage:-lgcov} \
       %{fopenacc|fopenmp|%:gt(%{ftree-parallelize-loops=*:%*} 1): \
@@ -412,15 +418,15 @@  extern GTY(()) int darwin_ms_struct;
       %(link_ssp) \
       %:version-compare(>< 10.6 10.7 mmacosx-version-min= -ld10-uwfef) \
       %(link_gcc_c_sequence) \
-      %{!nodefaultexport:%{dylib|dynamiclib|bundle: \
-	%:version-compare(>= 10.11 asm_macosx_version_min= -U) \
-	%:version-compare(>= 10.11 asm_macosx_version_min= ___emutls_get_address) \
-	%:version-compare(>= 10.11 asm_macosx_version_min= -exported_symbol) \
-	%:version-compare(>= 10.11 asm_macosx_version_min= ___emutls_get_address) \
-	%:version-compare(>= 10.11 asm_macosx_version_min= -U) \
-	%:version-compare(>= 10.11 asm_macosx_version_min= ___emutls_register_common) \
-	%:version-compare(>= 10.11 asm_macosx_version_min= -exported_symbol) \
-	%:version-compare(>= 10.11 asm_macosx_version_min= ___emutls_register_common) \
+      %{!nodefaultexport: \
+	%{%:version-compare(>= 10.11 asm_macosx_version_min= -U): \
+	   ___emutls_get_address -exported_symbol ___emutls_get_address \
+	  -U ___emutls_register_common \
+	  -exported_symbol ___emutls_register_common \
+	  -U ___gcc_nested_func_ptr_created \
+	  -exported_symbol ___gcc_nested_func_ptr_created \
+	  -U ___gcc_nested_func_ptr_deleted \
+	  -exported_symbol ___gcc_nested_func_ptr_deleted \
       }} \
     }}}\
     %{!r:%{!nostdlib:%{!nostartfiles:%E}}} %{T*} %{F*} "\
@@ -542,16 +548,21 @@  extern GTY(()) int darwin_ms_struct;
 #undef REAL_LIBGCC_SPEC
 #define REAL_LIBGCC_SPEC \
 "%{static-libgcc|static:						  \
-    %:version-compare(!> 10.6 mmacosx-version-min= -lgcc_eh)		  \
-    %:version-compare(>= 10.6 mmacosx-version-min= -lemutls_w);		  \
+    %:version-compare(!> 10.6 mmacosx-version-min= -lgcc_eh);		  \
    shared-libgcc|fexceptions|fobjc-exceptions|fgnu-runtime:		  \
    " DARWIN_SHARED_LIBGCC "						  \
     %:version-compare(!> 10.3.9 mmacosx-version-min= -lgcc_eh)		  \
     %:version-compare(>< 10.3.9 10.5 mmacosx-version-min= -lgcc_s.10.4)   \
-    %:version-compare(>< 10.5 10.6 mmacosx-version-min= -lgcc_s.10.5);	  \
-   : -lemutls_w								  \
+    %:version-compare(>< 10.5 10.6 mmacosx-version-min= -lgcc_s.10.5)	  \
   } -lgcc "
 
+#define DARWIN_WEAK_CRTS \
+"%{static-libgcc|static:						  \
+    %{%:version-compare(>= 10.6 mmacosx-version-min= -lemutls_w):	  \
+      " DARWIN_HEAP_T_LIB "} ;						  \
+   : -lemutls_w	" DARWIN_HEAP_T_LIB "					  \
+  }"
+
 /* We specify crt0.o as -lcrt0.o so that ld will search the library path.  */
 
 #undef  STARTFILE_SPEC
diff --git a/gcc/config/i386/darwin.h b/gcc/config/i386/darwin.h
index b7814f7c42e..8e64b4e9b5f 100644
--- a/gcc/config/i386/darwin.h
+++ b/gcc/config/i386/darwin.h
@@ -119,6 +119,8 @@  along with GCC; see the file COPYING3.  If not see
 /* We default to x86_64 for single-arch builds, bi-arch overrides.  */
 #define DARWIN_ARCH_SPEC "x86_64"
 #define DARWIN_SUBARCH_SPEC DARWIN_ARCH_SPEC
+#undef DARWIN_HEAP_T_LIB
+#define DARWIN_HEAP_T_LIB " -lheapt_w "
 #endif
 
 #undef SUBTARGET_EXTRA_SPECS
diff --git a/gcc/config/i386/darwin32-biarch.h b/gcc/config/i386/darwin32-biarch.h
index 051ad12b425..2180f5a5352 100644
--- a/gcc/config/i386/darwin32-biarch.h
+++ b/gcc/config/i386/darwin32-biarch.h
@@ -27,6 +27,9 @@  along with GCC; see the file COPYING3.  If not see
 #undef  DARWIN_SUBARCH_SPEC
 #define DARWIN_SUBARCH_SPEC DARWIN_ARCH_SPEC
 
+#undef DARWIN_HEAP_T_LIB
+#define DARWIN_HEAP_T_LIB " %{m64:-lheapt_w}"
+
 #undef SUBTARGET_EXTRA_SPECS
 #define SUBTARGET_EXTRA_SPECS                                   \
   DARWIN_EXTRA_SPECS                                            \
diff --git a/gcc/config/i386/darwin64-biarch.h b/gcc/config/i386/darwin64-biarch.h
index 85436791a6c..620800749a8 100644
--- a/gcc/config/i386/darwin64-biarch.h
+++ b/gcc/config/i386/darwin64-biarch.h
@@ -28,6 +28,9 @@  along with GCC; see the file COPYING3.  If not see
 #undef  DARWIN_SUBARCH_SPEC
 #define DARWIN_SUBARCH_SPEC DARWIN_ARCH_SPEC
 
+#undef DARWIN_HEAP_T_LIB
+#define DARWIN_HEAP_T_LIB "%{!m32:-lheapt_w}"
+
 #undef SUBTARGET_EXTRA_SPECS
 #define SUBTARGET_EXTRA_SPECS                                   \
   DARWIN_EXTRA_SPECS                                            \
diff --git a/gcc/config/rs6000/darwin.h b/gcc/config/rs6000/darwin.h
index b264284100f..e8b194982b4 100644
--- a/gcc/config/rs6000/darwin.h
+++ b/gcc/config/rs6000/darwin.h
@@ -113,6 +113,9 @@ 
   -lSystem								\
 }"
 
+#undef DARWIN_HEAP_T_LIB
+#define DARWIN_HEAP_T_LIB " "
+
 /* We want -fPIC by default, unless we're using -static to compile for
    the kernel or some such.  The "-faltivec" option should have been
    called "-maltivec" all along.  */
diff --git a/libgcc/config.host b/libgcc/config.host
index 017fbc7a06d..3e7d00f67aa 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -715,12 +715,15 @@  hppa*-*-netbsd*)
 i[34567]86-*-darwin*)
 	tmake_file="$tmake_file i386/t-crtpc t-crtfm i386/t-msabi"
 	tm_file="$tm_file i386/darwin-lib.h"
-	extra_parts="$extra_parts crtprec32.o crtprec64.o crtprec80.o crtfastmath.o"
+	extra_parts="$extra_parts crtprec32.o crtprec64.o crtprec80.o"
+	extra_parts="$extra_parts crtfastmath.o libheapt_w.a"
+	tmake_file="${tmake_file} i386/t-heap-trampoline"
 	;;
 x86_64-*-darwin*)
 	tmake_file="$tmake_file i386/t-crtpc t-crtfm i386/t-msabi"
 	tm_file="$tm_file i386/darwin-lib.h"
-	extra_parts="$extra_parts crtprec32.o crtprec64.o crtprec80.o crtfastmath.o"
+	extra_parts="$extra_parts crtprec32.o crtprec64.o crtprec80.o"
+	extra_parts="$extra_parts crtfastmath.o libheapt_w.a"
 	tmake_file="${tmake_file} i386/t-heap-trampoline"
 	;;
 i[34567]86-*-elfiamcu)
diff --git a/libgcc/config/aarch64/heap-trampoline.c b/libgcc/config/aarch64/heap-trampoline.c
index 2041fe6aa39..b463399c1e9 100644
--- a/libgcc/config/aarch64/heap-trampoline.c
+++ b/libgcc/config/aarch64/heap-trampoline.c
@@ -15,6 +15,12 @@ 
 #include <pthread.h>
 #endif
 
+/* HEAP_T_ATTR is provided to allow targets to build the exported functions
+   as weak definitions.  */
+#ifndef HEAP_T_ATTR
+#  define HEAP_T_ATTR
+#endif
+
 void *allocate_trampoline_page (void);
 int get_trampolines_per_page (void);
 struct tramp_ctrl_data *allocate_tramp_ctrl (struct tramp_ctrl_data *parent);
@@ -107,6 +113,7 @@  allocate_tramp_ctrl (struct tramp_ctrl_data *parent)
   return p;
 }
 
+HEAP_T_ATTR
 void
 __gcc_nested_func_ptr_created (void *chain, void *func, void **dst)
 {
@@ -154,6 +161,7 @@  __gcc_nested_func_ptr_created (void *chain, void *func, void **dst)
   *dst = &trampoline->insns;
 }
 
+HEAP_T_ATTR
 void
 __gcc_nested_func_ptr_deleted (void)
 {
diff --git a/libgcc/config/i386/heap-trampoline.c b/libgcc/config/i386/heap-trampoline.c
index 726cf55277a..4e069c458a7 100644
--- a/libgcc/config/i386/heap-trampoline.c
+++ b/libgcc/config/i386/heap-trampoline.c
@@ -15,6 +15,12 @@ 
 #include <pthread.h>
 #endif
 
+/* HEAP_T_ATTR is provided to allow targets to build the exported functions
+   as weak definitions.  */
+#ifndef HEAP_T_ATTR
+#  define HEAP_T_ATTR
+#endif
+
 void *allocate_trampoline_page (void);
 int get_trampolines_per_page (void);
 struct tramp_ctrl_data *allocate_tramp_ctrl (struct tramp_ctrl_data *parent);
@@ -107,6 +113,7 @@  allocate_tramp_ctrl (struct tramp_ctrl_data *parent)
   return p;
 }
 
+HEAP_T_ATTR
 void
 __gcc_nested_func_ptr_created (void *chain, void *func, void **dst)
 {
@@ -154,6 +161,7 @@  __gcc_nested_func_ptr_created (void *chain, void *func, void **dst)
   *dst = &trampoline->insns;
 }
 
+HEAP_T_ATTR
 void
 __gcc_nested_func_ptr_deleted (void)
 {
diff --git a/libgcc/config/t-darwin b/libgcc/config/t-darwin
index a3bb70c6a0a..0f65b54a230 100644
--- a/libgcc/config/t-darwin
+++ b/libgcc/config/t-darwin
@@ -51,5 +51,18 @@  LIB2ADDEH = $(srcdir)/unwind-dw2.c \
 # Do not build a shared unwind lib by default.
 LIBEHSOBJS=
 
+# Make heap trampoline helpers weak definitions so that we can merge them from
+# multiple DSOs.
+heap-trampoline.o: HOST_LIBGCC2_CFLAGS += \
+  -DHEAP_T_ATTR='__attribute__((__weak__,__visibility__("default")))'
+heap-trampoline_s.o: HOST_LIBGCC2_CFLAGS += \
+  -DHEAP_T_ATTR='__attribute__((__weak__,__visibility__("default")))'
+
+# Make a heap trampoline support CRT so that it can be linked optionally, use
+# the shared version so that we can link with DSOs.
+libheapt_w.a: heap-trampoline_s.o
+	$(AR_CREATE_FOR_TARGET) $@ $<
+	$(RANLIB_FOR_TARGET) $@
+
 # Symbols for all the sub-ports.
 SHLIB_MAPFILES = libgcc-std.ver $(srcdir)/config/libgcc-libsystem.ver