Add a BTI sysarch

[andrew]

Summary

This is used to enable the guard page when an elf binary is built with
BTI instructions.

Sponsored by: Arm Ltd
Sponsored by: The FreeBSD Foundation

[andrew]

• Rebase on D42328
• Move ARM64_GUARD_PAGE from 0 to ensure userspace intends to set it

[markj]

Where will BTI be documented? Perhaps bti.3 and mitigations.7?

sys/arm64/arm64/sys_machdep.c

48

74

IMO it is clearer to write this in terms of a range:

sva = trunc_page(gp_args.addr);
eva = round_page(gp_args.addr + gp_args.len);
if (sva > eva || eva > VM_MAX_USER_ADDRESS)
    return (EINVAL);
error = pmap_pti_set(pmap, sva, eva);

76

Shouldn't the pmap should be derived from td, not using pcpu? This looks strange, I don't know why PKRU does it this way.

77

pmap_bti_set() returns 0 if the executable didn't have BTI configured. Don't we want to return an error here in that case?

sys/arm64/include/sysarch.h

42

What is this constant for?

[andrew]

Updates based on feedback from @markj.

Only page align the start and end address when calling pmap_bti_set to ensure we catch address space overflows

[markj]

sys/arm64/arm64/sys_machdep.c

53

All of the other error cases below are handled by returning directly.

sys/arm64/arm64/sys_machdep.c

 #define LINUX_PTRACE_GETREGS            12
 #define LINUX_PTRACE_SETREGS            13
 #define LINUX_PTRACE_GETFPREGS          14
 #define LINUX_PTRACE_SETFPREGS          15
 #define LINUX_PTRACE_ATTACH             16
 #define LINUX_PTRACE_DETACH             17
 #define LINUX_PTRACE_SYSCALL            24
 #define LINUX_PTRACE_SETOPTIONS         0x4200
+#define LINUX_PTRACE_GETSIGINFO         0x4202
 #define LINUX_PTRACE_GETREGSET          0x4204
 #define LINUX_PTRACE_SEIZE              0x4206
 
 #define LINUX_PTRACE_O_TRACESYSGOOD     1
 #define LINUX_PTRACE_O_TRACEFORK        2
 #define LINUX_PTRACE_O_TRACEVFORK       4
 #define LINUX_PTRACE_O_TRACECLONE       8
 #define LINUX_PTRACE_O_TRACEEXEC        16
linux_msg(td, "PTRACE_O_TRACEEXIT not implemented; "
                     "returning EINVAL");
                 return (EINVAL);
         }
 
         return (kern_ptrace(td, PT_SET_EVENT_MASK, pid, &mask, sizeof(mask)));
 }
 
 static int
+linux_ptrace_getsiginfo(struct thread *td, pid_t pid, l_ulong data)
+{
+        struct ptrace_lwpinfo lwpinfo;
+        l_siginfo_t l_siginfo;
+        int error, sig;
+
+        error = kern_ptrace(td, PT_LWPINFO, pid, &lwpinfo, sizeof(lwpinfo));
+        if (error != 0) {
+                linux_msg(td, "PT_LWPINFO failed with error %d", error);
+                return (error);
+        }
+
+        if ((lwpinfo.pl_flags & PL_FLAG_SI) == 0) {
+                error = EINVAL;
+                linux_msg(td, "no PL_FLAG_SI, returning %d", error);
+                return (error);
+        }
+
+        sig = bsd_to_linux_signal(lwpinfo.pl_siginfo.si_signo);
+        siginfo_to_lsiginfo(&lwpinfo.pl_siginfo, &l_siginfo, sig);
+        error = copyout(&l_siginfo, (void *)data, sizeof(l_siginfo));
+        return (error);
+}
+
+static int
 linux_ptrace_getregs(struct thread *td, pid_t pid, void *data)
 {
         struct ptrace_lwpinfo lwpinfo;
         struct reg b_reg;
         struct linux_pt_reg l_reg;
         int error;
 
         error = kern_ptrace(td, PT_GETREGS, pid, &b_reg, 0);
linux_ptrace(struct thread *td, struct linux_ptrace_args *uap)
         case LINUX_PTRACE_SYSCALL:
                 error = map_signum(uap->data, &sig);
                 if (error != 0)
                         break;
                 error = kern_ptrace(td, PT_SYSCALL, pid, (void *)1, sig);
                 break;
         case LINUX_PTRACE_SETOPTIONS:
                 error = linux_ptrace_setoptions(td, pid, uap->data);
+                break;
+        case LINUX_PTRACE_GETSIGINFO:
+                error = linux_ptrace_getsiginfo(td, pid, uap->data);
                 break;
         case LINUX_PTRACE_GETREGSET:
                 error = linux_ptrace_getregset(td, pid, uap->addr, uap->data);
                 break;
         case LINUX_PTRACE_SEIZE:
                 error = linux_ptrace_seize(td, pid, uap->addr, uap->data);
                 break;
         default:
                 linux_msg(td, "ptrace(%ld, ...) not implemented; "
                     "returning EINVAL", uap->req);
                 error = EINVAL;
                 break;
         }
 
         return (error);
 }

sys/arm64/include/sysarch.h

 #define LINUX_PTRACE_GETREGS            12
 #define LINUX_PTRACE_SETREGS            13
 #define LINUX_PTRACE_GETFPREGS          14
 #define LINUX_PTRACE_SETFPREGS          15
 #define LINUX_PTRACE_ATTACH             16
 #define LINUX_PTRACE_DETACH             17
 #define LINUX_PTRACE_SYSCALL            24
 #define LINUX_PTRACE_SETOPTIONS         0x4200
+#define LINUX_PTRACE_GETSIGINFO         0x4202
 #define LINUX_PTRACE_GETREGSET          0x4204
 #define LINUX_PTRACE_SEIZE              0x4206
 
 #define LINUX_PTRACE_O_TRACESYSGOOD     1
 #define LINUX_PTRACE_O_TRACEFORK        2
 #define LINUX_PTRACE_O_TRACEVFORK       4
 #define LINUX_PTRACE_O_TRACECLONE       8
 #define LINUX_PTRACE_O_TRACEEXEC        16
linux_msg(td, "PTRACE_O_TRACEEXIT not implemented; "
                     "returning EINVAL");
                 return (EINVAL);
         }
 
         return (kern_ptrace(td, PT_SET_EVENT_MASK, pid, &mask, sizeof(mask)));
 }
 
 static int
+linux_ptrace_getsiginfo(struct thread *td, pid_t pid, l_ulong data)
+{
+        struct ptrace_lwpinfo lwpinfo;
+        l_siginfo_t l_siginfo;
+        int error, sig;
+
+        error = kern_ptrace(td, PT_LWPINFO, pid, &lwpinfo, sizeof(lwpinfo));
+        if (error != 0) {
+                linux_msg(td, "PT_LWPINFO failed with error %d", error);
+                return (error);
+        }
+
+        if ((lwpinfo.pl_flags & PL_FLAG_SI) == 0) {
+                error = EINVAL;
+                linux_msg(td, "no PL_FLAG_SI, returning %d", error);
+                return (error);
+        }
+
+        sig = bsd_to_linux_signal(lwpinfo.pl_siginfo.si_signo);
+        siginfo_to_lsiginfo(&lwpinfo.pl_siginfo, &l_siginfo, sig);
+        error = copyout(&l_siginfo, (void *)data, sizeof(l_siginfo));
+        return (error);
+}
+
+static int
 linux_ptrace_getregs(struct thread *td, pid_t pid, void *data)
 {
         struct ptrace_lwpinfo lwpinfo;
         struct reg b_reg;
         struct linux_pt_reg l_reg;
         int error;
 
         error = kern_ptrace(td, PT_GETREGS, pid, &b_reg, 0);
linux_ptrace(struct thread *td, struct linux_ptrace_args *uap)
         case LINUX_PTRACE_SYSCALL:
                 error = map_signum(uap->data, &sig);
                 if (error != 0)
                         break;
                 error = kern_ptrace(td, PT_SYSCALL, pid, (void *)1, sig);
                 break;
         case LINUX_PTRACE_SETOPTIONS:
                 error = linux_ptrace_setoptions(td, pid, uap->data);
+                break;
+        case LINUX_PTRACE_GETSIGINFO:
+                error = linux_ptrace_getsiginfo(td, pid, uap->data);
                 break;
         case LINUX_PTRACE_GETREGSET:
                 error = linux_ptrace_getregset(td, pid, uap->addr, uap->data);
                 break;
         case LINUX_PTRACE_SEIZE:
                 error = linux_ptrace_seize(td, pid, uap->addr, uap->data);
                 break;
         default:
                 linux_msg(td, "ptrace(%ld, ...) not implemented; "
                     "returning EINVAL", uap->req);
                 error = EINVAL;
                 break;
         }
 
         return (error);
 }