From: Mike Frysinger <vap...@gentoo.org> The current code will load the stack size and protection markings, but then only use the markings in the MMU code path. The NOMMU code path always passes PROT_EXEC to the mmap() call. While this doesn't matter to most people whilst the code is running, it will cause a pointless icache flush when starting every FDPIC application. Typically this icache flush will be of a region on the order of 128KB in size, or may be the entire icache, depending on the facilities available on the CPU.
In the case where the arch default behaviour seems to be desired (EXSTACK_DEFAULT), we probe VM_STACK_FLAGS for VM_EXEC to determine whether we should be setting PROT_EXEC or not. For arches that support an MPU (Memory Protection Unit - an MMU without the virtual mapping capability), setting PROT_EXEC or not will make an important difference. It should be noted that this change also affects the executability of the brk region, since ELF-FDPIC has that share with the stack. However, this is probably irrelevant as NOMMU programs aren't likely to use the brk region, preferring instead allocation via mmap(). Signed-off-by: Mike Frysinger <vap...@gentoo.org> Signed-off-by: David Howells <dhowe...@redhat.com> --- arch/blackfin/include/asm/page.h | 5 +++++ arch/frv/include/asm/page.h | 2 -- fs/binfmt_elf_fdpic.c | 13 +++++++++++-- 3 files changed, 16 insertions(+), 4 deletions(-) diff --git a/arch/blackfin/include/asm/page.h b/arch/blackfin/include/asm/page.h index 944a07c..1d04e40 100644 --- a/arch/blackfin/include/asm/page.h +++ b/arch/blackfin/include/asm/page.h @@ -10,4 +10,9 @@ #include <asm-generic/page.h> #define MAP_NR(addr) (((unsigned long)(addr)-PAGE_OFFSET) >> PAGE_SHIFT) +#define VM_DATA_DEFAULT_FLAGS \ + (VM_READ | VM_WRITE | \ + ((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0 ) | \ + VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC) + #endif diff --git a/arch/frv/include/asm/page.h b/arch/frv/include/asm/page.h index 25c6a50..8c97068 100644 --- a/arch/frv/include/asm/page.h +++ b/arch/frv/include/asm/page.h @@ -63,12 +63,10 @@ extern unsigned long max_pfn; #define virt_addr_valid(kaddr) pfn_valid(__pa(kaddr) >> PAGE_SHIFT) -#ifdef CONFIG_MMU #define VM_DATA_DEFAULT_FLAGS \ (VM_READ | VM_WRITE | \ ((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0 ) | \ VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC) -#endif #endif /* __ASSEMBLY__ */ diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c index 7dc8599..c57d9ce 100644 --- a/fs/binfmt_elf_fdpic.c +++ b/fs/binfmt_elf_fdpic.c @@ -171,6 +171,9 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm, #ifdef ELF_FDPIC_PLAT_INIT unsigned long dynaddr; #endif +#ifndef CONFIG_MMU + unsigned long stack_prot; +#endif struct file *interpreter = NULL; /* to shut gcc up */ char *interpreter_name = NULL; int executable_stack; @@ -316,6 +319,8 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm, * defunct, deceased, etc. after this point we have to exit via * error_kill */ set_personality(PER_LINUX_FDPIC); + if (elf_read_implies_exec(&exec_params.hdr, executable_stack)) + current->personality |= READ_IMPLIES_EXEC; set_binfmt(&elf_fdpic_format); current->mm->start_code = 0; @@ -377,9 +382,13 @@ static int load_elf_fdpic_binary(struct linux_binprm *bprm, if (stack_size < PAGE_SIZE * 2) stack_size = PAGE_SIZE * 2; + stack_prot = PROT_READ | PROT_WRITE; + if (executable_stack == EXSTACK_ENABLE_X || + (executable_stack == EXSTACK_DEFAULT && VM_STACK_FLAGS & VM_EXEC)) + stack_prot |= PROT_EXEC; + down_write(¤t->mm->mmap_sem); - current->mm->start_brk = do_mmap(NULL, 0, stack_size, - PROT_READ | PROT_WRITE | PROT_EXEC, + current->mm->start_brk = do_mmap(NULL, 0, stack_size, stack_prot, MAP_PRIVATE | MAP_ANONYMOUS | MAP_UNINITIALIZED | MAP_GROWSDOWN, 0); _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev