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linux/arch/x86/include/asm/ptrace.h
Tejun Heo b9cd18de4d ptrace,x86: force IRET path after a ptrace_stop() 
The 'sysret' fastpath does not correctly restore even all regular
registers, much less any segment registers or reflags values.  That is
very much part of why it's faster than 'iret'.

Normally that isn't a problem, because the normal ptrace() interface
catches the process using the signal handler infrastructure, which
always returns with an iret.

However, some paths can get caught using ptrace_event() instead of the
signal path, and for those we need to make sure that we aren't going to
return to user space using 'sysret'.  Otherwise the modifications that
may have been done to the register set by the tracer wouldn't
necessarily take effect.

Fix it by forcing IRET path by setting TIF_NOTIFY_RESUME from
arch_ptrace_stop_needed() which is invoked from ptrace_stop().

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Andy Lutomirski <luto@amacapital.net>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-07-03 17:27:23 -07:00

258 lines
6.8 KiB
C
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#ifndef _ASM_X86_PTRACE_H
#define _ASM_X86_PTRACE_H
#include <asm/segment.h>
#include <asm/page_types.h>
#include <uapi/asm/ptrace.h>
#ifndef __ASSEMBLY__
#ifdef __i386__
struct pt_regs {
unsigned long bx;
unsigned long cx;
unsigned long dx;
unsigned long si;
unsigned long di;
unsigned long bp;
unsigned long ax;
unsigned long ds;
unsigned long es;
unsigned long fs;
unsigned long gs;
unsigned long orig_ax;
unsigned long ip;
unsigned long cs;
unsigned long flags;
unsigned long sp;
unsigned long ss;
};
#else /* __i386__ */
struct pt_regs {
unsigned long r15;
unsigned long r14;
unsigned long r13;
unsigned long r12;
unsigned long bp;
unsigned long bx;
/* arguments: non interrupts/non tracing syscalls only save up to here*/
unsigned long r11;
unsigned long r10;
unsigned long r9;
unsigned long r8;
unsigned long ax;
unsigned long cx;
unsigned long dx;
unsigned long si;
unsigned long di;
unsigned long orig_ax;
/* end of arguments */
/* cpu exception frame or undefined */
unsigned long ip;
unsigned long cs;
unsigned long flags;
unsigned long sp;
unsigned long ss;
/* top of stack page */
};
#endif /* !__i386__ */
#ifdef CONFIG_PARAVIRT
#include <asm/paravirt_types.h>
#endif
struct cpuinfo_x86;
struct task_struct;
extern unsigned long profile_pc(struct pt_regs *regs);
#define profile_pc profile_pc
extern unsigned long
convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs);
extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
int error_code, int si_code);
extern long syscall_trace_enter(struct pt_regs *);
extern void syscall_trace_leave(struct pt_regs *);
static inline unsigned long regs_return_value(struct pt_regs *regs)
{
return regs->ax;
}
/*
* user_mode_vm(regs) determines whether a register set came from user mode.
* This is true if V8086 mode was enabled OR if the register set was from
* protected mode with RPL-3 CS value. This tricky test checks that with
* one comparison. Many places in the kernel can bypass this full check
* if they have already ruled out V8086 mode, so user_mode(regs) can be used.
*/
static inline int user_mode(struct pt_regs *regs)
{
#ifdef CONFIG_X86_32
return (regs->cs & SEGMENT_RPL_MASK) == USER_RPL;
#else
return !!(regs->cs & 3);
#endif
}
static inline int user_mode_vm(struct pt_regs *regs)
{
#ifdef CONFIG_X86_32
return ((regs->cs & SEGMENT_RPL_MASK) | (regs->flags & X86_VM_MASK)) >=
USER_RPL;
#else
return user_mode(regs);
#endif
}
static inline int v8086_mode(struct pt_regs *regs)
{
#ifdef CONFIG_X86_32
return (regs->flags & X86_VM_MASK);
#else
return 0; /* No V86 mode support in long mode */
#endif
}
#ifdef CONFIG_X86_64
static inline bool user_64bit_mode(struct pt_regs *regs)
{
#ifndef CONFIG_PARAVIRT
/*
* On non-paravirt systems, this is the only long mode CPL 3
* selector. We do not allow long mode selectors in the LDT.
*/
return regs->cs == __USER_CS;
#else
/* Headers are too twisted for this to go in paravirt.h. */
return regs->cs == __USER_CS || regs->cs == pv_info.extra_user_64bit_cs;
#endif
}
#define current_user_stack_pointer() this_cpu_read(old_rsp)
/* ia32 vs. x32 difference */
#define compat_user_stack_pointer() \
(test_thread_flag(TIF_IA32) \
? current_pt_regs()->sp \
: this_cpu_read(old_rsp))
#endif
#ifdef CONFIG_X86_32
extern unsigned long kernel_stack_pointer(struct pt_regs *regs);
#else
static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
{
return regs->sp;
}
#endif
#define GET_IP(regs) ((regs)->ip)
#define GET_FP(regs) ((regs)->bp)
#define GET_USP(regs) ((regs)->sp)
#include <asm-generic/ptrace.h>
/* Query offset/name of register from its name/offset */
extern int regs_query_register_offset(const char *name);
extern const char *regs_query_register_name(unsigned int offset);
#define MAX_REG_OFFSET (offsetof(struct pt_regs, ss))
/**
* regs_get_register() - get register value from its offset
* @regs: pt_regs from which register value is gotten.
* @offset: offset number of the register.
*
* regs_get_register returns the value of a register. The @offset is the
* offset of the register in struct pt_regs address which specified by @regs.
* If @offset is bigger than MAX_REG_OFFSET, this returns 0.
*/
static inline unsigned long regs_get_register(struct pt_regs *regs,
unsigned int offset)
{
if (unlikely(offset > MAX_REG_OFFSET))
return 0;
#ifdef CONFIG_X86_32
/*
* Traps from the kernel do not save sp and ss.
* Use the helper function to retrieve sp.
*/
if (offset == offsetof(struct pt_regs, sp) &&
regs->cs == __KERNEL_CS)
return kernel_stack_pointer(regs);
#endif
return *(unsigned long *)((unsigned long)regs + offset);
}
/**
* regs_within_kernel_stack() - check the address in the stack
* @regs: pt_regs which contains kernel stack pointer.
* @addr: address which is checked.
*
* regs_within_kernel_stack() checks @addr is within the kernel stack page(s).
* If @addr is within the kernel stack, it returns true. If not, returns false.
*/
static inline int regs_within_kernel_stack(struct pt_regs *regs,
unsigned long addr)
{
return ((addr & ~(THREAD_SIZE - 1)) ==
(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
}
/**
* regs_get_kernel_stack_nth() - get Nth entry of the stack
* @regs: pt_regs which contains kernel stack pointer.
* @n: stack entry number.
*
* regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
* is specified by @regs. If the @n th entry is NOT in the kernel stack,
* this returns 0.
*/
static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
unsigned int n)
{
unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
addr += n;
if (regs_within_kernel_stack(regs, (unsigned long)addr))
return *addr;
else
return 0;
}
#define arch_has_single_step() (1)
#ifdef CONFIG_X86_DEBUGCTLMSR
#define arch_has_block_step() (1)
#else
#define arch_has_block_step() (boot_cpu_data.x86 >= 6)
#endif
#define ARCH_HAS_USER_SINGLE_STEP_INFO
/*
* When hitting ptrace_stop(), we cannot return using SYSRET because
* that does not restore the full CPU state, only a minimal set. The
* ptracer can change arbitrary register values, which is usually okay
* because the usual ptrace stops run off the signal delivery path which
* forces IRET; however, ptrace_event() stops happen in arbitrary places
* in the kernel and don't force IRET path.
*
* So force IRET path after a ptrace stop.
*/
#define arch_ptrace_stop_needed(code, info) \
({ \
set_thread_flag(TIF_NOTIFY_RESUME); \
false; \
})
struct user_desc;
extern int do_get_thread_area(struct task_struct *p, int idx,
struct user_desc __user *info);
extern int do_set_thread_area(struct task_struct *p, int idx,
struct user_desc __user *info, int can_allocate);
#endif /* !__ASSEMBLY__ */
#endif /* _ASM_X86_PTRACE_H */
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