From: Jeff Dike Date: Thu, 1 Mar 2007 04:13:31 +0000 (-0800) Subject: [PATCH] uml: host VDSO fix X-Git-Tag: v2.6.21-rc3~163 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=14251809b1921b1216568700f1be2f91a1cbb5c7;p=linux-2.6 [PATCH] uml: host VDSO fix This fixes a problem seen by a number of people running UML on newer host kernels. init would hang with an infinite segfault loop. It turns out that the host kernel was providing a AT_SYSINFO_EHDR of 0xffffe000, which faked UML into believing that the host VDSO page could be reused. However, AT_SYSINFO pointed into the middle of the address space, and was unmapped as a result. Because UML was providing AT_SYSINFO_EHDR and AT_SYSINFO to its own processes, these would branch to nowhere when trying to use the VDSO. The fix is to also check the location of AT_SYSINFO when deciding whether to use the host's VDSO. Signed-off-by: Jeff Dike Cc: Paolo 'Blaisorblade' Giarrusso Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/um/os-Linux/elf_aux.c b/arch/um/os-Linux/elf_aux.c index 3a8d7e3aae..608784d4ec 100644 --- a/arch/um/os-Linux/elf_aux.c +++ b/arch/um/os-Linux/elf_aux.c @@ -39,6 +39,9 @@ __init void scan_elf_aux( char **envp) switch ( auxv->a_type ) { case AT_SYSINFO: __kernel_vsyscall = auxv->a_un.a_val; + /* See if the page is under TASK_SIZE */ + if (__kernel_vsyscall < (unsigned long) envp) + __kernel_vsyscall = 0; break; case AT_SYSINFO_EHDR: vsyscall_ehdr = auxv->a_un.a_val;