Commit 8797e1ca authored by Sven Schnelle's avatar Sven Schnelle Committed by Sasha Levin
Browse files

s390/ptrace: fix setting syscall number

[ Upstream commit 873e5a76

 ]

When strace wants to update the syscall number, it sets GPR2
to the desired number and updates the GPR via PTRACE_SETREGSET.
It doesn't update regs->int_code which would cause the old syscall
executed on syscall restart. As we cannot change the ptrace ABI and
don't have a field for the interruption code, check whether the tracee
is in a syscall and the last instruction was svc. In that case assume
that the tracer wants to update the syscall number and copy the GPR2
value to regs->int_code.
Signed-off-by: default avatarSven Schnelle <svens@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 2b0111cf
......@@ -324,6 +324,25 @@ static inline void __poke_user_per(struct task_struct *child,
child->thread.per_user.end = data;
}
static void fixup_int_code(struct task_struct *child, addr_t data)
{
struct pt_regs *regs = task_pt_regs(child);
int ilc = regs->int_code >> 16;
u16 insn;
if (ilc > 6)
return;
if (ptrace_access_vm(child, regs->psw.addr - (regs->int_code >> 16),
&insn, sizeof(insn), FOLL_FORCE) != sizeof(insn))
return;
/* double check that tracee stopped on svc instruction */
if ((insn >> 8) != 0xa)
return;
regs->int_code = 0x20000 | (data & 0xffff);
}
/*
* Write a word to the user area of a process at location addr. This
* operation does have an additional problem compared to peek_user.
......@@ -335,7 +354,9 @@ static int __poke_user(struct task_struct *child, addr_t addr, addr_t data)
struct user *dummy = NULL;
addr_t offset;
if (addr < (addr_t) &dummy->regs.acrs) {
struct pt_regs *regs = task_pt_regs(child);
/*
* psw and gprs are stored on the stack
*/
......@@ -353,7 +374,11 @@ static int __poke_user(struct task_struct *child, addr_t addr, addr_t data)
/* Invalid addressing mode bits */
return -EINVAL;
}
*(addr_t *)((addr_t) &task_pt_regs(child)->psw + addr) = data;
if (test_pt_regs_flag(regs, PIF_SYSCALL) &&
addr == offsetof(struct user, regs.gprs[2]))
fixup_int_code(child, data);
*(addr_t *)((addr_t) &regs->psw + addr) = data;
} else if (addr < (addr_t) (&dummy->regs.orig_gpr2)) {
/*
......@@ -719,6 +744,10 @@ static int __poke_user_compat(struct task_struct *child,
regs->psw.mask = (regs->psw.mask & ~PSW_MASK_BA) |
(__u64)(tmp & PSW32_ADDR_AMODE);
} else {
if (test_pt_regs_flag(regs, PIF_SYSCALL) &&
addr == offsetof(struct compat_user, regs.gprs[2]))
fixup_int_code(child, data);
/* gpr 0-15 */
*(__u32*)((addr_t) &regs->psw + addr*2 + 4) = tmp;
}
......
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