On Thu, Jun 22, 2017 at 11:57 PM, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > Hi Kees, > > On 22 June 2017 at 18:06, Kees Cook <keescook@xxxxxxxxxxxx> wrote: >> Now that explicitly executed loaders are loaded in the mmap region, >> position PIE binaries lower in the address space to avoid possible >> collisions with mmap or stack regions. For 64-bit, align to 4GB to >> allow runtimes to use the entire 32-bit address space for 32-bit >> pointers. >> >> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> >> --- >> arch/arm64/include/asm/elf.h | 13 ++++++------- >> 1 file changed, 6 insertions(+), 7 deletions(-) >> >> diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h >> index 5d1700425efe..f742af8f7c42 100644 >> --- a/arch/arm64/include/asm/elf.h >> +++ b/arch/arm64/include/asm/elf.h >> @@ -113,12 +113,13 @@ >> #define ELF_EXEC_PAGESIZE PAGE_SIZE >> >> /* >> - * This is the location that an ET_DYN program is loaded if exec'ed. Typical >> - * use of this is to invoke "./ld.so someprog" to test out a new version of >> - * the loader. We need to make sure that it is out of the way of the program >> - * that it will "exec", and that there is sufficient room for the brk. >> + * This is the base location for PIE (ET_DYN with INTERP) loads. On >> + * 64-bit, this is raised to 4GB to leave the entire 32-bit address >> + * space open for things that want to use the area for 32-bit pointers. >> */ >> -#define ELF_ET_DYN_BASE (2 * TASK_SIZE_64 / 3) >> +#define ELF_ET_DYN_BASE (test_thread_flag(TIF_32BIT) ? \ >> + 0x000400000UL : \ >> + 0x100000000UL) >> > > Why are you merging this with the COMPAT definition? It seemed like the right thing to do since a single definition could handle both cases. Is there something I'm overlooking in the arm64 case? -Kees > >> #ifndef __ASSEMBLY__ >> >> @@ -173,8 +174,6 @@ extern int arch_setup_additional_pages(struct linux_binprm *bprm, >> >> #ifdef CONFIG_COMPAT >> >> -#define COMPAT_ELF_ET_DYN_BASE (2 * TASK_SIZE_32 / 3) >> - >> /* AArch32 registers. */ >> #define COMPAT_ELF_NGREG 18 >> typedef unsigned int compat_elf_greg_t; >> -- >> 2.7.4 >> -- Kees Cook Pixel Security -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
