xiaoxiang781216 commented on code in PR #19940:
URL: https://github.com/apache/nuttx/pull/19940#discussion_r3906341706
##########
libs/libc/elf/gnu-elf.ld.in:
##########
@@ -98,7 +128,7 @@ SECTIONS
. = ALIGN(SECTIONS_ALIGN);
_efini = .;
_edtors = .;
- }
+ } PHDR_DATA
.bss :
Review Comment:
should we move .bss to the end
##########
arch/arm/src/common/Toolchain.defs:
##########
@@ -633,6 +633,14 @@ CELFFLAGS = $(filter-out --fixed-r9,$(CFLAGS))
-fvisibility=hidden \
CXXELFFLAGS = $(filter-out --fixed-r9,$(CXXFLAGS)) -fvisibility=hidden \
-mlong-calls
+# -fno-use-cxa-atexit, because the default registers each static object's
+# destructor with __cxa_atexit(dtor, obj, &__dso_handle), and __dso_handle
+# comes from crtbegin, which a module does not link. Turning it off also
+# puts the destructors in .fini_array, which is where the loader looks for
+# them when the module is unloaded.
+
+CXXELFFLAGS += -fno-use-cxa-atexit
Review Comment:
need modify cmakefile and other arch
##########
libs/libc/elf/gnu-elf.ld.in:
##########
@@ -111,12 +141,19 @@ SECTIONS
*(COMMON)
. = ALIGN(SECTIONS_ALIGN);
_ebss = . ;
- }
+ } PHDR_DATA
+
+#ifdef CONFIG_FDPIC
+ .dynamic :
+ {
+ *(.dynamic)
+ } :data :dynamic
Review Comment:
why put into teo sections
##########
arch/arm/src/common/Toolchain.defs:
##########
@@ -646,11 +646,29 @@ ifeq ($(CONFIG_PIC),y)
# after including this file, which would discard the flag.
ARCHCFLAGS += --fixed-r9
+
+ifeq ($(CONFIG_FDPIC),y)
+ # An FDPIC module is a shared object whose two segments the loader places
+ # independently. The stock compiler emits correct FDPIC objects for both C
+ # and C++, so only the link needs the arm-uclinuxfdpiceabi linker: the
+ # stock one carries the armelf emulation alone and would turn every import
+ # into a jump slot where the ABI wants a function descriptor.
+
+ FDPIC_CROSSDEV ?= arm-uclinuxfdpiceabi-
+ MODULELD = $(FDPIC_CROSSDEV)ld
+
+ CELFFLAGS += -mfdpic -fPIC -Wa,--noexecstack
Review Comment:
why not reference PICFLAGS
##########
arch/arm/src/cmake/elf.cmake:
##########
@@ -27,17 +27,54 @@ nuttx_mod_compile_options(-fvisibility=hidden -mlong-calls)
nuttx_elf_compile_options_ifdef(CONFIG_UNWINDER_ARM -fno-unwind-tables
-fno-asynchronous-unwind-tables)
-# An ELF module needs r9 as its PIC base, so it must not also have the register
-# fixed: GCC rejects that pair with "unable to use 'r9' for PIC register".
This
-# mirrors CELFFLAGS in common/Toolchain.defs, which filters --fixed-r9 back out
-# of the inherited CFLAGS for the same reason.
+# -fno-use-cxa-atexit, because the default registers each static object's
+# destructor with __cxa_atexit(dtor, obj, &__dso_handle), and __dso_handle
comes
+# from crtbegin, which a module does not link. Turning it off also puts the
+# destructors in .fini_array, which is where the loader looks for them when the
+# module is unloaded. This mirrors CXXELFFLAGS in common/Toolchain.defs.
-nuttx_elf_compile_options_ifdef(CONFIG_PIC -mpic-register=r9)
+nuttx_elf_compile_options(-fno-use-cxa-atexit)
-nuttx_elf_link_options_ifdef(
- CONFIG_PIC --unresolved-symbols=ignore-in-object-files --emit-relocs)
+if(CONFIG_FDPIC)
-nuttx_elf_link_options_ifdef(CONFIG_BINFMT_ELF_RELOCATABLE -r)
+ # An FDPIC module is a shared object whose two segments the loader places
+ # independently. The stock compiler emits correct FDPIC objects for both C
+ # and C++, so only the link needs the arm-uclinuxfdpiceabi linker: the stock
+ # one carries the armelf emulation alone and would turn every import into a
+ # jump slot where the ABI wants a function descriptor.
+
+ if(NOT FDPIC_CROSSDEV)
+ set(FDPIC_CROSSDEV arm-uclinuxfdpiceabi-)
+ endif()
+
+ set(CMAKE_ELF_LD
+ "${FDPIC_CROSSDEV}ld"
+ CACHE INTERNAL "Linker for FDPIC modules")
+
+ nuttx_elf_compile_options(-mfdpic -fPIC -Wa,--noexecstack)
+
+ nuttx_elf_link_options(-m armelf_linux_fdpiceabi -shared -z now)
+
+else()
Review Comment:
add if CONFIG_PIC and remove ifdef suffix at line 65 and 67
##########
arch/arm/src/cmake/elf.cmake:
##########
@@ -27,17 +27,54 @@ nuttx_mod_compile_options(-fvisibility=hidden -mlong-calls)
nuttx_elf_compile_options_ifdef(CONFIG_UNWINDER_ARM -fno-unwind-tables
-fno-asynchronous-unwind-tables)
-# An ELF module needs r9 as its PIC base, so it must not also have the register
-# fixed: GCC rejects that pair with "unable to use 'r9' for PIC register".
This
-# mirrors CELFFLAGS in common/Toolchain.defs, which filters --fixed-r9 back out
-# of the inherited CFLAGS for the same reason.
+# -fno-use-cxa-atexit, because the default registers each static object's
+# destructor with __cxa_atexit(dtor, obj, &__dso_handle), and __dso_handle
comes
+# from crtbegin, which a module does not link. Turning it off also puts the
+# destructors in .fini_array, which is where the loader looks for them when the
+# module is unloaded. This mirrors CXXELFFLAGS in common/Toolchain.defs.
-nuttx_elf_compile_options_ifdef(CONFIG_PIC -mpic-register=r9)
+nuttx_elf_compile_options(-fno-use-cxa-atexit)
-nuttx_elf_link_options_ifdef(
- CONFIG_PIC --unresolved-symbols=ignore-in-object-files --emit-relocs)
+if(CONFIG_FDPIC)
-nuttx_elf_link_options_ifdef(CONFIG_BINFMT_ELF_RELOCATABLE -r)
+ # An FDPIC module is a shared object whose two segments the loader places
+ # independently. The stock compiler emits correct FDPIC objects for both C
+ # and C++, so only the link needs the arm-uclinuxfdpiceabi linker: the stock
+ # one carries the armelf emulation alone and would turn every import into a
+ # jump slot where the ABI wants a function descriptor.
+
+ if(NOT FDPIC_CROSSDEV)
+ set(FDPIC_CROSSDEV arm-uclinuxfdpiceabi-)
+ endif()
+
+ set(CMAKE_ELF_LD
+ "${FDPIC_CROSSDEV}ld"
+ CACHE INTERNAL "Linker for FDPIC modules")
+
+ nuttx_elf_compile_options(-mfdpic -fPIC -Wa,--noexecstack)
+
+ nuttx_elf_link_options(-m armelf_linux_fdpiceabi -shared -z now)
+
+else()
+
+ # An ELF module needs r9 as its PIC base, so it must not also have the
+ # register fixed: GCC rejects that pair with "unable to use 'r9' for PIC
+ # register". This mirrors CELFFLAGS in common/Toolchain.defs, which filters
+ # --fixed-r9 back out of the inherited CFLAGS for the same reason.
+
+ nuttx_elf_compile_options_ifdef(CONFIG_PIC -mpic-register=r9)
+
+ nuttx_elf_link_options_ifdef(
+ CONFIG_PIC --unresolved-symbols=ignore-in-object-files --emit-relocs)
+
+endif()
+
+# Not with CONFIG_PIC: there the module is linked as an executable, which is
+# what common/Toolchain.defs does too.
+
+if(CONFIG_BINFMT_ELF_RELOCATABLE AND NOT CONFIG_PIC)
Review Comment:
why need check pic
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