From 50f72b57946d565db74fae71bac23f3f319311c8 Mon Sep 17 00:00:00 2001 From: Jeff Dike Date: Sun, 9 Oct 2005 16:11:44 -0400 Subject: [PATCH] [PATCH] uml: fix x86_64 with !CONFIG_FRAME_POINTER UML/x86_64 doesn't run when built with frame pointers disabled. There was an implicit frame pointer assumption in the stub segfault handler. With frame pointers disabled, UML dies on handling its first page fault. The container-of part of this is from Paolo Giarrusso . Signed-off-by: Jeff Dike Signed-off-by: Linus Torvalds --- arch/um/sys-x86_64/stub_segv.c | 37 +++++++++++++++++++++++++--------- 1 file changed, 28 insertions(+), 9 deletions(-) diff --git a/arch/um/sys-x86_64/stub_segv.c b/arch/um/sys-x86_64/stub_segv.c index 65a131b362b6..d1e53bdf2e85 100644 --- a/arch/um/sys-x86_64/stub_segv.c +++ b/arch/um/sys-x86_64/stub_segv.c @@ -10,6 +10,22 @@ #include "uml-config.h" #include "sysdep/sigcontext.h" #include "sysdep/faultinfo.h" +#include + +/* Copied from sys-x86_64/signal.c - Can't find an equivalent definition + * in the libc headers anywhere. + */ +struct rt_sigframe +{ + char *pretcode; + struct ucontext uc; + struct siginfo info; +}; + +/* Copied here from - we're userspace. */ +#define container_of(ptr, type, member) ({ \ + const typeof( ((type *)0)->member ) *__mptr = (ptr); \ + (type *)( (char *)__mptr - offsetof(type,member) );}) void __attribute__ ((__section__ (".__syscall_stub"))) stub_segv_handler(int sig) @@ -17,16 +33,19 @@ stub_segv_handler(int sig) struct ucontext *uc; __asm__("movq %%rdx, %0" : "=g" (uc) :); - GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA), - &uc->uc_mcontext); + GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA), + &uc->uc_mcontext); - __asm__("movq %0, %%rax ; syscall": : "g" (__NR_getpid)); + __asm__("movq %0, %%rax ; syscall": : "g" (__NR_getpid)); __asm__("movq %%rax, %%rdi ; movq %0, %%rax ; movq %1, %%rsi ;" - "syscall": : "g" (__NR_kill), "g" (SIGUSR1)); - /* Two popqs to restore the stack to the state just before entering - * the handler, one pops the return address, the other pops the frame - * pointer. + "syscall": : "g" (__NR_kill), "g" (SIGUSR1) : + "%rdi", "%rax", "%rsi"); + /* sys_sigreturn expects that the stack pointer will be 8 bytes into + * the signal frame. So, we use the ucontext pointer, which we know + * already, to get the signal frame pointer, and add 8 to that. */ - __asm__("popq %%rax ; popq %%rax ; movq %0, %%rax ; syscall" : : "g" - (__NR_rt_sigreturn)); + __asm__("movq %0, %%rsp": : + "g" ((unsigned long) container_of(uc, struct rt_sigframe, + uc) + 8)); + __asm__("movq %0, %%rax ; syscall" : : "g" (__NR_rt_sigreturn)); }