diff options
Diffstat (limited to 'aarch64-Make-elf_machine_-load_address-dynamic-robus.patch')
| -rw-r--r-- | aarch64-Make-elf_machine_-load_address-dynamic-robus.patch | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/aarch64-Make-elf_machine_-load_address-dynamic-robus.patch b/aarch64-Make-elf_machine_-load_address-dynamic-robus.patch new file mode 100644 index 0000000..b178499 --- /dev/null +++ b/aarch64-Make-elf_machine_-load_address-dynamic-robus.patch @@ -0,0 +1,72 @@ +From 43d06ed218fc8be58987bdfd00e21e5720f0b862 Mon Sep 17 00:00:00 2001 +From: Fangrui Song <maskray@google.com> +Date: Wed, 11 Aug 2021 09:00:37 -0700 +Subject: [PATCH] aarch64: Make elf_machine_{load_address,dynamic} robust [BZ + #28203] + +The AArch64 ABI is largely platform agnostic and does not specify +_GLOBAL_OFFSET_TABLE_[0] ([1]). glibc ld.so turns out to be probably the +only user of _GLOBAL_OFFSET_TABLE_[0] and GNU ld defines the value +to the link-time address _DYNAMIC. [2] + +In 2012, __ehdr_start was implemented in GNU ld and gold in binutils +2.23. Using adrp+add / (-mcmodel=tiny) adr to access +__ehdr_start/_DYNAMIC gives us a robust way to get the load address and +the link-time address of _DYNAMIC. + +[1]: From a psABI maintainer, https://bugs.llvm.org/show_bug.cgi?id=49672#c2 +[2]: LLD's aarch64 port does not set _GLOBAL_OFFSET_TABLE_[0] to the +link-time address _DYNAMIC. +LLD is widely used on aarch64 Android and ChromeOS devices. Software +just works without the need for _GLOBAL_OFFSET_TABLE_[0]. + +Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com> +--- + sysdeps/aarch64/dl-machine.h | 24 +++++++++--------------- + 1 file changed, 9 insertions(+), 15 deletions(-) + +diff --git a/sysdeps/aarch64/dl-machine.h b/sysdeps/aarch64/dl-machine.h +index d29d827..3e10cb4 100644 +--- a/sysdeps/aarch64/dl-machine.h ++++ b/sysdeps/aarch64/dl-machine.h +@@ -37,28 +37,22 @@ elf_machine_matches_host (const ElfW(Ehdr) *ehdr) + return ehdr->e_machine == EM_AARCH64; + } + +-/* Return the link-time address of _DYNAMIC. Conveniently, this is the +- first element of the GOT. */ +-static inline ElfW(Addr) __attribute__ ((unused)) +-elf_machine_dynamic (void) +-{ +- extern const ElfW(Addr) _GLOBAL_OFFSET_TABLE_[] attribute_hidden; +- return _GLOBAL_OFFSET_TABLE_[0]; +-} +- + /* Return the run-time load address of the shared object. */ + + static inline ElfW(Addr) __attribute__ ((unused)) + elf_machine_load_address (void) + { +- /* To figure out the load address we use the definition that for any symbol: +- dynamic_addr(symbol) = static_addr(symbol) + load_addr ++ extern const ElfW(Ehdr) __ehdr_start attribute_hidden; ++ return (ElfW(Addr)) &__ehdr_start; ++} + +- _DYNAMIC sysmbol is used here as its link-time address stored in +- the special unrelocated first GOT entry. */ ++/* Return the link-time address of _DYNAMIC. */ + +- extern ElfW(Dyn) _DYNAMIC[] attribute_hidden; +- return (ElfW(Addr)) &_DYNAMIC - elf_machine_dynamic (); ++static inline ElfW(Addr) __attribute__ ((unused)) ++elf_machine_dynamic (void) ++{ ++ extern ElfW(Dyn) _DYNAMIC[] attribute_hidden; ++ return (ElfW(Addr)) _DYNAMIC - elf_machine_load_address (); + } + + /* Set up the loaded object described by L so its unrelocated PLT +-- +1.8.3.1 + |