From 547ee84cea37696d25c93306e909378a87db2f66 Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Sat, 16 Apr 2005 15:24:35 -0700 Subject: [PATCH] ppc64: Improve mapping of vDSO This patch reworks the way the ppc64 is mapped in user memory by the kernel to make it more robust against possible collisions with executable segments. Instead of just whacking a VMA at 1Mb, I now use get_unmapped_area() with a hint, and I moved the mapping of the vDSO to after the mapping of the various ELF segments and of the interpreter, so that conflicts get caught properly (it still has to be before create_elf_tables since the later will fill the AT_SYSINFO_EHDR with the proper address). While I was at it, I also changed the 32 and 64 bits vDSO's to link at their "natural" address of 1Mb instead of 0. This is the address where they are normally mapped in absence of conflict. By doing so, it should be possible to properly prelink one it's been verified to work on glibc. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/ppc64/kernel/vdso.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) (limited to 'arch/ppc64/kernel') diff --git a/arch/ppc64/kernel/vdso.c b/arch/ppc64/kernel/vdso.c index 8c4597224b71..4777676365fe 100644 --- a/arch/ppc64/kernel/vdso.c +++ b/arch/ppc64/kernel/vdso.c @@ -213,13 +213,14 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int executable_stack) vdso_base = VDSO64_MBASE; } + current->thread.vdso_base = 0; + /* vDSO has a problem and was disabled, just don't "enable" it for the * process */ - if (vdso_pages == 0) { - current->thread.vdso_base = 0; + if (vdso_pages == 0) return 0; - } + vma = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); if (vma == NULL) return -ENOMEM; @@ -230,12 +231,16 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int executable_stack) memset(vma, 0, sizeof(*vma)); /* - * pick a base address for the vDSO in process space. We have a default - * base of 1Mb on which we had a random offset up to 1Mb. - * XXX: Add possibility for a program header to specify that location + * pick a base address for the vDSO in process space. We try to put it + * at vdso_base which is the "natural" base for it, but we might fail + * and end up putting it elsewhere. */ + vdso_base = get_unmapped_area(NULL, vdso_base, + vdso_pages << PAGE_SHIFT, 0, 0); + if (vdso_base & ~PAGE_MASK) + return (int)vdso_base; + current->thread.vdso_base = vdso_base; - /* + ((unsigned long)vma & 0x000ff000); */ vma->vm_mm = mm; vma->vm_start = current->thread.vdso_base; -- cgit v1.2.3-59-g8ed1b