Architectures such as i386, sh, x86_64 have a flag /proc/sys/vm/vdso_enabled to choose whether the kernel should setup a process to use vdso after execve(). Informing the user code via AT_SYSINFO* is controlled by macro ARCH_DLINFO in fs/binfmt_elf.c and include/asm-$ARCH/elf.h, but the vdso page is established always via arch_setup_additonal_pages() called from load_elf_binary(). If vdso_enabled is off, then current code wastes kernel time during execve() and fragments the address space unnecessarily.
This patch changes arch_setup_additonal_pages() to honor vdso_enabled. For i386 it also allows the option of a fixed addresss to avoid fragmenting the address space. Compiles and runs on i386. x86_64 [IA32 support] and sh maintainers also please comment. For some related history, including interaction with exec-shield, see: http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=229304 and also 207020 and 162797. Signed-off-by: John Reiser <[EMAIL PROTECTED]> diff --git a/arch/i386/kernel/sysenter.c b/arch/i386/kernel/sysenter.c index 13ca54a..f8c4d76 100644 --- a/arch/i386/kernel/sysenter.c +++ b/arch/i386/kernel/sysenter.c @@ -22,6 +22,8 @@ #include <asm/msr.h> #include <asm/pgtable.h> #include <asm/unistd.h> +#include <asm/a.out.h> +#include <asm/mman.h> /* * Should the kernel map a VDSO page into processes and pass its @@ -105,10 +107,25 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int exstack) { struct mm_struct *mm = current->mm; unsigned long addr; + unsigned long flags; int ret; + switch (vdso_enabled) { + case 0: /* none */ + return 0; + default: + case 1: /* vdso in random available page */ + addr = 0ul; + flags = 0ul; + break; + case 2: /* out of user's way */ + addr = STACK_TOP; + flags = MAP_FIXED; + break; + } + down_write(&mm->mmap_sem); - addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); + addr = get_unmapped_area(NULL, addr, PAGE_SIZE, 0, flags); if (IS_ERR_VALUE(addr)) { ret = addr; goto up_fail; diff --git a/arch/sh/kernel/vsyscall/vsyscall.c b/arch/sh/kernel/vsyscall/vsyscall.c index 7b0f66f..2b789fb 100644 --- a/arch/sh/kernel/vsyscall/vsyscall.c +++ b/arch/sh/kernel/vsyscall/vsyscall.c @@ -64,6 +64,9 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, unsigned long addr; int ret; + if (!vdso_enabled) + return 0; + down_write(&mm->mmap_sem); addr = get_unmapped_area(NULL, 0, PAGE_SIZE, 0, 0); if (IS_ERR_VALUE(addr)) { diff --git a/include/asm-i386/a.out.h b/include/asm-i386/a.out.h index ab17bb8..9894f73 100644 --- a/include/asm-i386/a.out.h +++ b/include/asm-i386/a.out.h @@ -19,7 +19,7 @@ struct exec #ifdef __KERNEL__ -#define STACK_TOP TASK_SIZE +#define STACK_TOP (TASK_SIZE - PAGE_SIZE) /* 1 page optional for vdso */ #endif -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
