executor, sys/linux, pkg: enable syzos for riscv64

This patch enables syzos for riscv64 and implements
the corresponding pseudo syscalls.

Pseudo syscalls:
  - syz_kvm_setup_syzos_vm
  - syz_kvm_add_vcpu
  - syz_kvm_assert_syzos_uexit

Syzos guest support:
  - guest_uexit
  - guest_execute_code
  - guest_handle_csrr and guest_handle_csrw

Test seeds:
  - riscv64-syz_kvm_setup_syzos_vm
  - riscv64-syz_kvm_setup_syzos_vm-csrr
  - riscv64-syz_kvm_setup_syzos_vm-csrw

5 files changed, 135 insertions, 1 deletions

diff --git a/sys/linux/dev_kvm.txt b/sys/linux/dev_kvm.txt
index a3d646efb..3b4a6b04d 100644
--- a/sys/linux/dev_kvm.txt
+++ b/sys/linux/dev_kvm.txt
@@ -644,7 +644,7 @@ kvm_regs_arm64_extra = 0x603000000013c01b, 0x603000000013c01f, 0x603000000013c02
 # For riscv64, the following ids are computed from arch/riscv/include/uapi/asm/kvm.h and arch/riscv/include/uapi/asm/ptrace.h .
 kvm_regs_riscv64_config = 0x8030000000100000, 0x8030000000100001, 0x8030000000100002, 0x8030000000100003, 0x8030000000100004, 0x8030000000100005, 0x8030000000100006, 0x8030000000100007
 kvm_regs_riscv64_core = 0x8030000000200000, 0x8030000000200001, 0x8030000000200002, 0x8030000000200003, 0x8030000000200004, 0x8030000000200005, 0x8030000000200006, 0x8030000000200007, 0x8030000000200008, 0x8030000000200009, 0x803000000020000a, 0x803000000020000b, 0x803000000020000c, 0x803000000020000d, 0x803000000020000e, 0x803000000020000f, 0x8030000000200010, 0x8030000000200011, 0x8030000000200012, 0x8030000000200013, 0x8030000000200014, 0x8030000000200015, 0x8030000000200016, 0x8030000000200017, 0x8030000000200018, 0x8030000000200019, 0x803000000020001a, 0x803000000020001b, 0x803000000020001c, 0x803000000020001d, 0x803000000020001e, 0x803000000020001f, 0x8030000000200020
-kvm_regs_riscv64_csr = 0x8030000000300000, 0x8030000000300001, 0x8030000000300002, 0x8030000000300003, 0x8030000000300004, 0x8030000000300005, 0x8030000000300006, 0x8030000000300007, 0x8030000000300008
+kvm_regs_riscv64_csr = 0x8030000000300000, 0x8030000000300001, 0x8030000000300002, 0x8030000000300003, 0x8030000000300004, 0x8030000000300005, 0x8030000000300006, 0x8030000000300007, 0x8030000000300008, 0x8030000000300009, 0x803000000030000a
 kvm_regs_riscv64_aia_csr = 0x8030000003010000, 0x8030000003010001, 0x8030000003010002, 0x8030000003010003, 0x8030000003010004, 0x8030000003010005, 0x8030000003010006
 kvm_regs_riscv64_smstateen_csr = 0x8030000003020000
 kvm_regs_riscv64_timer = 0x8030000004000000, 0x8030000004000001, 0x8030000004000002, 0x8030000004000003
diff --git a/sys/linux/dev_kvm_riscv64.txt b/sys/linux/dev_kvm_riscv64.txt
index 5e7e508a9..9c1dea7d9 100644
--- a/sys/linux/dev_kvm_riscv64.txt
+++ b/sys/linux/dev_kvm_riscv64.txt
@@ -32,4 +32,60 @@ kvm_text_riscv64 {
 	size	len[text, intptr]
 }
 
+# kvm_syz_vm is a VM handler used by syzos-related pseudo-syscalls. It is actually an opaque pointer under the hood.
+resource kvm_syz_vm$riscv64[int64]
+
+# Map the given memory into the VM and set up syzos there.
+syz_kvm_setup_syzos_vm$riscv64(fd fd_kvmvm, usermem vma[1024]) kvm_syz_vm$riscv64
+
+# Create a VCPU inside a kvm_syz_vm VM.
+# Prohibit flattening the input arguments, so that it is easier to reason about them.
+syz_kvm_add_vcpu$riscv64(vm kvm_syz_vm$riscv64, text ptr[in, kvm_text_syzos_riscv64], opts ptr[in, array[kvm_setup_opt_riscv64, 1]], nopt len[opts]) fd_kvmcpu (no_squash)
+
+kvm_text_syzos_riscv64 {
+	typ	const[0, intptr]
+	text	ptr[in, array[syzos_api_call$riscv64, 1:32]]
+	size	bytesize[text, int64]
+}
+
+type syzos_api$riscv64[NUM, PAYLOAD] {
+	call	const[NUM, int64]
+	size	bytesize[parent, int64]
+	payload	PAYLOAD
+}
+
+syzos_api_code$riscv64 {
+	insns	text[riscv64]
+	ret	const[0x8067, int32]
+} [packed]
+
+syzos_api_csrr {
+	arg_reg	riscv64_csr_or_any
+}
+
+syzos_api_csrw {
+	arg_reg		riscv64_csr_or_any
+	arg_value	int64
+}
+
+riscv64_csr_or_any [
+	valid	flags[riscv64_csr, int64]
+	any	int64
+]
+
+# Table 5 in https://docs.riscv.org/reference/isa/_attachments/riscv-privileged.pdf .
+# Currently, only 11 CSRS are supported in Linux-6.19. See
+# https://elixir.bootlin.com/linux/v6.19-rc5/source/arch/riscv/include/uapi/asm/kvm.h#L75 .
+riscv64_csr = 0x100, 0x104, 0x105, 0x140, 0x141, 0x142, 0x143, 0x144, 0x180, 0x106, 0x10a
+
+syzos_api_call$riscv64 [
+	uexit	syzos_api$riscv64[0, intptr]
+	code	syzos_api$riscv64[10, syzos_api_code$riscv64]
+	csrr	syzos_api$riscv64[100, syzos_api_csrr]
+	csrw	syzos_api$riscv64[101, syzos_api_csrw]
+] [varlen]
+
+# Test assertions, will not be used by the fuzzer.
 syz_kvm_assert_reg$riscv64(fd fd_kvmcpu, reg int64, value int64) (no_generate)
+syz_kvm_assert_syzos_uexit$riscv64(cpufd fd_kvmcpu, run kvm_run_ptr, exitcode int64) (no_generate)
+syz_kvm_assert_syzos_kvm_exit$riscv64(run kvm_run_ptr, exitcode int64) (no_generate)
diff --git a/sys/linux/test/riscv64-syz_kvm_setup_syzos_vm b/sys/linux/test/riscv64-syz_kvm_setup_syzos_vm
new file mode 100644
index 000000000..5942f1b9f
--- /dev/null
+++ b/sys/linux/test/riscv64-syz_kvm_setup_syzos_vm
@@ -0,0 +1,35 @@
+#
+# requires: arch=riscv64 -threaded
+#
+
+r0 = openat$kvm(0, &AUTO='/dev/kvm\x00', 0x0, 0x0)
+r1 = ioctl$KVM_CREATE_VM(r0, AUTO, 0x0)
+r2 = syz_kvm_setup_syzos_vm$riscv64(r1, &(0x7f0000c00000/0x400000)=nil)
+
+# Perform two uexits. The first one is done via a code blob:
+#       lui   a0, 0x40000
+#       addi  a0, a0, 0x100        # a0 = RISCV64_ADDR_UEXIT
+#       sd    zero, 0(a0)
+#       ret
+# The second uexit is done via a syzos API command that sets uexit exit code to 0xaaaa.
+#
+r3 = syz_kvm_add_vcpu$riscv64(r2, &AUTO={0x0, &AUTO=[@code={AUTO, AUTO, {"370500401305051023300500", 0x00008067}}, @uexit={AUTO, AUTO, 0xaaaa}], AUTO}, 0x0, 0x0)
+
+r4 = ioctl$KVM_GET_VCPU_MMAP_SIZE(r0, AUTO)
+r5 = mmap$KVM_VCPU(&(0x7f0000009000/0x1000)=nil, r4, 0x3, 0x1, r3, 0x0)
+
+# Run till the first uexit.
+#
+ioctl$KVM_RUN(r3, AUTO, 0x0)
+syz_kvm_assert_syzos_uexit$riscv64(r3, r5, 0x0)
+# Run till the second uexit.
+#
+ioctl$KVM_RUN(r3, AUTO, 0x0)
+syz_kvm_assert_syzos_uexit$riscv64(r3, r5, 0xaaaa)
+# Run till the end of guest_main(). 0xffffffffffffffff is UEXIT_END.
+#
+ioctl$KVM_RUN(r3, AUTO, 0x0)
+# Ensure that exit reason is KVM_EXIT_MMIO and uexit code is UEXIT_END.
+#
+syz_kvm_assert_syzos_kvm_exit$riscv64(r5, 0x6)
+syz_kvm_assert_syzos_uexit$riscv64(r3, r5, 0xffffffffffffffff)
diff --git a/sys/linux/test/riscv64-syz_kvm_setup_syzos_vm-csrr b/sys/linux/test/riscv64-syz_kvm_setup_syzos_vm-csrr
new file mode 100644
index 000000000..77ea424df
--- /dev/null
+++ b/sys/linux/test/riscv64-syz_kvm_setup_syzos_vm-csrr
@@ -0,0 +1,21 @@
+#
+# requires: arch=riscv64 -threaded
+#
+
+# This test verifies that SYZOS can safely execute CSR access instructions
+# inside a RISC-V KVM guest.
+#
+r0 = openat$kvm(0, &AUTO='/dev/kvm\x00', 0x0, 0x0)
+r1 = ioctl$KVM_CREATE_VM(r0, AUTO, 0x0)
+r2 = syz_kvm_setup_syzos_vm$riscv64(r1, &(0x7f0000c00000/0x400000)=nil)
+
+# Number 0x140 is sscratch (encode).
+#
+r3 = syz_kvm_add_vcpu$riscv64(r2, &AUTO={0x0, &AUTO=[@csrr={AUTO, AUTO, {@valid=0x140}}], AUTO}, 0x0, 0x0)
+r4 = ioctl$KVM_GET_VCPU_MMAP_SIZE(r0, AUTO)
+r5 = mmap$KVM_VCPU(&(0x7f0000009000/0x1000)=nil, r4, 0x3, 0x1, r3, 0x0)
+
+# Run till end of guest_main().
+#
+ioctl$KVM_RUN(r3, AUTO, 0x0)
+syz_kvm_assert_syzos_uexit$riscv64(r3, r5, 0xffffffffffffffff)
diff --git a/sys/linux/test/riscv64-syz_kvm_setup_syzos_vm-csrw b/sys/linux/test/riscv64-syz_kvm_setup_syzos_vm-csrw
new file mode 100644
index 000000000..38fdd4929
--- /dev/null
+++ b/sys/linux/test/riscv64-syz_kvm_setup_syzos_vm-csrw
@@ -0,0 +1,22 @@
+#
+# requires: arch=riscv64 -threaded
+#
+
+# This test verifies that writing a supervisor CSR from the guest is
+# correctly reflected in the KVM vCPU state.
+#
+r0 = openat$kvm(0, &AUTO='/dev/kvm\x00', 0x0, 0x0)
+r1 = ioctl$KVM_CREATE_VM(r0, AUTO, 0x0)
+r2 = syz_kvm_setup_syzos_vm$riscv64(r1, &(0x7f0000c00000/0x400000)=nil)
+
+# Number 0x140 is sscratch (encode).
+#
+r3 = syz_kvm_add_vcpu$riscv64(r2, &AUTO={0x0, &AUTO=[@csrw={AUTO, AUTO, {@valid=0x140, 0xfefefee0}}], AUTO}, 0x0, 0x0)
+r4 = ioctl$KVM_GET_VCPU_MMAP_SIZE(r0, AUTO)
+r5 = mmap$KVM_VCPU(&(0x7f0000009000/0x1000)=nil, r4, 0x3, 0x1, r3, 0x0)
+ioctl$KVM_RUN(r3, AUTO, 0x0)
+syz_kvm_assert_syzos_uexit$riscv64(r3, r5, 0xffffffffffffffff)
+
+# ID 0x8030000003000003 is sscratch (kvm reg id).
+#
+syz_kvm_assert_reg$riscv64(r3, 0x8030000003000003, 0xfefefee0)