syscall: Expect ID to be passed in a7

This is consistent with Linux and pk and may help with adding compatibility in the future.

2 files changed, 3 insertions, 3 deletions

diff --git a/src/lib/interrupts.zig b/src/lib/interrupts.zig
index a91e079..1750b5b 100644
--- a/src/lib/interrupts.zig
+++ b/src/lib/interrupts.zig
@@ -156,8 +156,8 @@ export fn handleTrap(epc: usize, tval: usize, cause_bits: usize, frame: *trap.Fr
             .ecall => {
                 syscall.handle(frame) catch |err| switch (err) {
                     syscall.Error.UnknownSyscall => {
-                        const a0 = frame.general_purpose_registers[10];
-                        w.print("Hart {d}: Unknown syscall, a0 = 0x{x:0>16}\r\n", .{ frame.hart_id, a0 }) catch unreachable;
+                        const a7 = frame.general_purpose_registers[17];
+                        w.print("Hart {d}: Unknown syscall, a7 = 0x{x:0>16}\r\n", .{ frame.hart_id, a7 }) catch unreachable;
                     },
                 };
 
diff --git a/src/lib/syscall.zig b/src/lib/syscall.zig
index 692507e..8f30972 100644
--- a/src/lib/syscall.zig
+++ b/src/lib/syscall.zig
@@ -9,7 +9,7 @@ pub const Error = error{
 };
 
 pub fn handle(trap_frame: *const trap.Frame) !void {
-    switch (trap_frame.general_purpose_registers[10]) {
+    switch (trap_frame.general_purpose_registers[17]) {
         else => return Error.UnknownSyscall,
     }
 }