niansa-misc/linux
1
0
Fork 0
mirror of synced 2025-03-06 20:59:54 +01:00
Code Issues Projects Releases Packages Wiki Activity
linux/arch/mips/include/asm/ptrace.h
Maciej W. Rozycki ed975485a1 MIPS: Export syscall stack arguments properly for remote use 
We have several places across the kernel where we want to access another
task's syscall arguments, such as ptrace(2), seccomp(2), etc., by making
a call to syscall_get_arguments().

This works for register arguments right away by accessing the task's
`regs' member of `struct pt_regs', however for stack arguments seen with
32-bit/o32 kernels things are more complicated.  Technically they ought
to be obtained from the user stack with calls to an access_remote_vm(),
but we have an easier way available already.

So as to be able to access syscall stack arguments as regular function
arguments following the MIPS calling convention we copy them over from
the user stack to the kernel stack in arch/mips/kernel/scall32-o32.S, in
handle_sys(), to the current stack frame's outgoing argument space at
the top of the stack, which is where the handler called expects to see
its incoming arguments.  This area is also pointed at by the `pt_regs'
pointer obtained by task_pt_regs().

Make the o32 stack argument space a proper member of `struct pt_regs'
then, by renaming the existing member from `pad0' to `args' and using
generated offsets to access the space.  No functional change though.

With the change in place the o32 kernel stack frame layout at the entry
to a syscall handler invoked by handle_sys() is therefore as follows:

$sp + 68 -> |         ...         | <- pt_regs.regs[9]
            +---------------------+
$sp + 64 -> |         $t0         | <- pt_regs.regs[8]
            +---------------------+
$sp + 60 -> |   $a3/argument #4   | <- pt_regs.regs[7]
            +---------------------+
$sp + 56 -> |   $a2/argument #3   | <- pt_regs.regs[6]
            +---------------------+
$sp + 52 -> |   $a1/argument #2   | <- pt_regs.regs[5]
            +---------------------+
$sp + 48 -> |   $a0/argument #1   | <- pt_regs.regs[4]
            +---------------------+
$sp + 44 -> |         $v1         | <- pt_regs.regs[3]
            +---------------------+
$sp + 40 -> |         $v0         | <- pt_regs.regs[2]
            +---------------------+
$sp + 36 -> |         $at         | <- pt_regs.regs[1]
            +---------------------+
$sp + 32 -> |        $zero        | <- pt_regs.regs[0]
            +---------------------+
$sp + 28 -> |  stack argument #8  | <- pt_regs.args[7]
            +---------------------+
$sp + 24 -> |  stack argument #7  | <- pt_regs.args[6]
            +---------------------+
$sp + 20 -> |  stack argument #6  | <- pt_regs.args[5]
            +---------------------+
$sp + 16 -> |  stack argument #5  | <- pt_regs.args[4]
            +---------------------+
$sp + 12 -> | psABI space for $a3 | <- pt_regs.args[3]
            +---------------------+
$sp +  8 -> | psABI space for $a2 | <- pt_regs.args[2]
            +---------------------+
$sp +  4 -> | psABI space for $a1 | <- pt_regs.args[1]
            +---------------------+
$sp +  0 -> | psABI space for $a0 | <- pt_regs.args[0]
            +---------------------+

holding user data received and with the first 4 frame slots reserved by
the psABI for the compiler to spill the incoming arguments from $a0-$a3
registers (which it sometimes does according to its needs) and the next
4 frame slots designated by the psABI for any stack function arguments
that follow.  This data is also available for other tasks to peek/poke
at as reqired and where permitted.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
2025-02-13 12:41:18 +01:00

192 lines
5.5 KiB
C
Raw Blame History

/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 1994, 95, 96, 97, 98, 99, 2000 by Ralf Baechle
* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
*/
#ifndef _ASM_PTRACE_H
#define _ASM_PTRACE_H
#include <linux/compiler.h>
#include <linux/linkage.h>
#include <linux/types.h>
#include <asm/isadep.h>
#include <asm/page.h>
#include <asm/thread_info.h>
#include <uapi/asm/ptrace.h>
/*
* This struct defines the way the registers are stored on the stack during a
* system call/exception. As usual the registers k0/k1 aren't being saved.
*
* If you add a register here, also add it to regoffset_table[] in
* arch/mips/kernel/ptrace.c.
*/
struct pt_regs {
#ifdef CONFIG_32BIT
/* Saved syscall stack arguments; entries 0-3 unused. */
unsigned long args[8];
#endif
/* Saved main processor registers. */
unsigned long regs[32];
/* Saved special registers. */
unsigned long cp0_status;
unsigned long hi;
unsigned long lo;
#ifdef CONFIG_CPU_HAS_SMARTMIPS
unsigned long acx;
#endif
unsigned long cp0_badvaddr;
unsigned long cp0_cause;
unsigned long cp0_epc;
#ifdef CONFIG_CPU_CAVIUM_OCTEON
unsigned long long mpl[6]; /* MTM{0-5} */
unsigned long long mtp[6]; /* MTP{0-5} */
#endif
unsigned long __last[0];
} __aligned(8);
static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
{
return regs->regs[29];
}
static inline void instruction_pointer_set(struct pt_regs *regs,
unsigned long val)
{
regs->cp0_epc = val;
regs->cp0_cause &= ~CAUSEF_BD;
}
/* Query offset/name of register from its name/offset */
extern int regs_query_register_offset(const char *name);
#define MAX_REG_OFFSET (offsetof(struct pt_regs, __last))
/**
* 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;
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;
}
struct task_struct;
extern int ptrace_getregs(struct task_struct *child,
struct user_pt_regs __user *data);
extern int ptrace_setregs(struct task_struct *child,
struct user_pt_regs __user *data);
extern int ptrace_getfpregs(struct task_struct *child, __u32 __user *data);
extern int ptrace_setfpregs(struct task_struct *child, __u32 __user *data);
extern int ptrace_get_watch_regs(struct task_struct *child,
struct pt_watch_regs __user *addr);
extern int ptrace_set_watch_regs(struct task_struct *child,
struct pt_watch_regs __user *addr);
/*
* Does the process account for user or for system time?
*/
#define user_mode(regs) (((regs)->cp0_status & KU_MASK) == KU_USER)
static inline int is_syscall_success(struct pt_regs *regs)
{
return !regs->regs[7];
}
static inline long regs_return_value(struct pt_regs *regs)
{
if (is_syscall_success(regs) || !user_mode(regs))
return regs->regs[2];
else
return -regs->regs[2];
}
#define instruction_pointer(regs) ((regs)->cp0_epc)
extern unsigned long exception_ip(struct pt_regs *regs);
#define exception_ip(regs) exception_ip(regs)
#define profile_pc(regs) instruction_pointer(regs)
extern asmlinkage long syscall_trace_enter(struct pt_regs *regs);
extern asmlinkage void syscall_trace_leave(struct pt_regs *regs);
extern void die(const char *, struct pt_regs *) __noreturn;
static inline void die_if_kernel(const char *str, struct pt_regs *regs)
{
if (unlikely(!user_mode(regs)))
die(str, regs);
}
#define current_pt_regs() \
({ \
unsigned long sp = (unsigned long)__builtin_frame_address(0); \
(struct pt_regs *)((sp | (THREAD_SIZE - 1)) + 1 - 32) - 1; \
})
/* Helpers for working with the user stack pointer */
static inline unsigned long user_stack_pointer(struct pt_regs *regs)
{
return regs->regs[29];
}
static inline void user_stack_pointer_set(struct pt_regs *regs,
unsigned long val)
{
regs->regs[29] = val;
}
#endif /* _ASM_PTRACE_H */
Reference in a new issue View git blame Copy permalink