[adding Andi and Ingo] John Reiser wrote: > 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 >
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