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authorSven Schnelle <svens@linux.ibm.com>2020-03-09 16:44:50 +0100
committerVasily Gorbik <gor@linux.ibm.com>2020-06-16 13:44:04 +0200
commit873e5a763d604c32988c4a78913a8dab3862d2f9 (patch)
treeb9f89c12afdd3f5268c507b9424fadb922c9f9c5 /arch
parent00332c16b1604242a56289ff2b26e283dbad0812 (diff)
s390/ptrace: fix setting syscall number
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: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/s390/kernel/ptrace.c31
1 files changed, 30 insertions, 1 deletions
diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 1fdbb2d19477..3cc15c066298 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -323,6 +323,25 @@ 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.
@@ -334,7 +353,9 @@ 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
*/
@@ -352,7 +373,11 @@ 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)) {
/*
@@ -718,6 +743,10 @@ 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;
}