2f56debd77
Commit ee3d9bd4de ("uml: simplify SIGSEGV
handling"), while greatly simplifying the kernel SIGSEGV handler that
runs in the process address space, introduced a bug which corrupts FP
state in the process.
Previously, the SIGSEGV handler called the sigreturn system call by hand - it
couldn't return through the restorer provided to it because that could try to
call the libc restorer which likely wouldn't exist in the process address
space. So, it blocked off some signals, including SIGUSR1, on entry to the
SIGSEGV handler, queued a SIGUSR1 to itself, and invoked sigreturn. The
SIGUSR1 was delivered, and was visible to the UML kernel after sigreturn
finished.
The commit eliminated the signal masking and the call to sigreturn. The
handler simply hits itself with a SIGTRAP to let the UML kernel know that it
is finished. UML then restores the process registers, which effectively
longjmps the process out of the signal handler, skipping sigreturn's restoring
of register state and the signal mask.
The bug is that the host apparently sets used_fp to 0 when it saves the
process FP state in the sigcontext on the process signal stack. Thus, when
the process is longjmped out of the handler, its FP state is corrupt because
it wasn't saved on the context switch to the UML kernel.
This manifested itself as sleep hanging. For some reason, sleep uses floating
point in order to calculate the sleep interval. When a page fault corrupts
its FP state, it is faked into essentially sleeping forever.
This patch saves the FP state before entering the SIGSEGV handler and restores
it afterwards.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
87 lines
2.5 KiB
C
87 lines
2.5 KiB
C
/*
|
|
* Copyright 2003 PathScale, Inc.
|
|
*
|
|
* Licensed under the GPL
|
|
*/
|
|
|
|
#ifndef __SYSDEP_X86_64_PTRACE_USER_H__
|
|
#define __SYSDEP_X86_64_PTRACE_USER_H__
|
|
|
|
#define __FRAME_OFFSETS
|
|
#include <sys/ptrace.h>
|
|
#include <linux/ptrace.h>
|
|
#include <asm/ptrace.h>
|
|
#undef __FRAME_OFFSETS
|
|
#include "user_constants.h"
|
|
|
|
#define PT_INDEX(off) ((off) / sizeof(unsigned long))
|
|
|
|
#define PT_SYSCALL_NR(regs) ((regs)[PT_INDEX(ORIG_RAX)])
|
|
#define PT_SYSCALL_NR_OFFSET (ORIG_RAX)
|
|
|
|
#define PT_SYSCALL_ARG1(regs) (((unsigned long *) (regs))[PT_INDEX(RDI)])
|
|
#define PT_SYSCALL_ARG1_OFFSET (RDI)
|
|
|
|
#define PT_SYSCALL_ARG2(regs) (((unsigned long *) (regs))[PT_INDEX(RSI)])
|
|
#define PT_SYSCALL_ARG2_OFFSET (RSI)
|
|
|
|
#define PT_SYSCALL_ARG3(regs) (((unsigned long *) (regs))[PT_INDEX(RDX)])
|
|
#define PT_SYSCALL_ARG3_OFFSET (RDX)
|
|
|
|
#define PT_SYSCALL_ARG4(regs) (((unsigned long *) (regs))[PT_INDEX(RCX)])
|
|
#define PT_SYSCALL_ARG4_OFFSET (RCX)
|
|
|
|
#define PT_SYSCALL_ARG5(regs) (((unsigned long *) (regs))[PT_INDEX(R8)])
|
|
#define PT_SYSCALL_ARG5_OFFSET (R8)
|
|
|
|
#define PT_SYSCALL_ARG6(regs) (((unsigned long *) (regs))[PT_INDEX(R9)])
|
|
#define PT_SYSCALL_ARG6_OFFSET (R9)
|
|
|
|
#define PT_SYSCALL_RET_OFFSET (RAX)
|
|
|
|
#define PT_IP_OFFSET (RIP)
|
|
#define PT_IP(regs) ((regs)[PT_INDEX(RIP)])
|
|
|
|
#define PT_SP_OFFSET (RSP)
|
|
#define PT_SP(regs) ((regs)[PT_INDEX(RSP)])
|
|
|
|
#define PT_ORIG_RAX_OFFSET (ORIG_RAX)
|
|
#define PT_ORIG_RAX(regs) ((regs)[PT_INDEX(ORIG_RAX)])
|
|
|
|
/* x86_64 FC3 doesn't define this in /usr/include/linux/ptrace.h even though
|
|
* it's defined in the kernel's include/linux/ptrace.h. Additionally, use the
|
|
* 2.4 name and value for 2.4 host compatibility.
|
|
*/
|
|
#ifndef PTRACE_OLDSETOPTIONS
|
|
#define PTRACE_OLDSETOPTIONS 21
|
|
#endif
|
|
|
|
/* These are before the system call, so the system call number is RAX
|
|
* rather than ORIG_RAX, and arg4 is R10 rather than RCX
|
|
*/
|
|
#define REGS_SYSCALL_NR PT_INDEX(RAX)
|
|
#define REGS_SYSCALL_ARG1 PT_INDEX(RDI)
|
|
#define REGS_SYSCALL_ARG2 PT_INDEX(RSI)
|
|
#define REGS_SYSCALL_ARG3 PT_INDEX(RDX)
|
|
#define REGS_SYSCALL_ARG4 PT_INDEX(R10)
|
|
#define REGS_SYSCALL_ARG5 PT_INDEX(R8)
|
|
#define REGS_SYSCALL_ARG6 PT_INDEX(R9)
|
|
|
|
#define REGS_IP_INDEX PT_INDEX(RIP)
|
|
#define REGS_SP_INDEX PT_INDEX(RSP)
|
|
|
|
#define FP_SIZE (HOST_FP_SIZE)
|
|
|
|
#endif
|
|
|
|
/*
|
|
* Overrides for Emacs so that we follow Linus's tabbing style.
|
|
* Emacs will notice this stuff at the end of the file and automatically
|
|
* adjust the settings for this buffer only. This must remain at the end
|
|
* of the file.
|
|
* ---------------------------------------------------------------------------
|
|
* Local variables:
|
|
* c-file-style: "linux"
|
|
* End:
|
|
*/
|