Daniel Samson
a5fe63c1dd
Processes now start with C-compatible arguments: the kernel builds the System V AMD64 entry block (argc, argv, empty envp, auxiliary vector) at the top of the stack, argv[0] is the path or initial-ramdisk name the process was spawned as, and system_spawn carries an optional NUL-separated blob that becomes argv[1..]. The runtime parses the block (runtime.argumentCount/argument) and its spawn wrappers pass arguments through. The name is also recorded on the task, so a fault report says which binary died, not just its id. The user stack grows from one page to eight (32 KiB, parameters.user_stack_pages), with the page below left unmapped as a guard so an overflow faults into a clean process kill rather than corrupting the image. Task.name_buffer is zero-initialised, not undefined: an undefined default is materialised as a 0xAA fill that moved the static task pool out of .bss and made the whole kernel ~7x slower under QEMU TCG (caught by the affinity test). Proven end to end by the new args test: args-echo respawns itself with arguments via the syscall blob, burns more stack than one page could hold, and echoes its argv intact. Full suite: 44/44.
56 lines
2.2 KiB
Zig
56 lines
2.2 KiB
Zig
//! args-echo — a test fixture for process arguments (bundled in the
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//! initial-ramdisk, spawned only by the `args` test case). Run with no arguments,
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//! it respawns itself *with* some via `spawnWithArguments` — exercising the
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//! system_spawn argument blob. Run with arguments, it burns more stack than one
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//! page could hold (proving the multi-page stack: on a single-page stack the
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//! recursion would hit the guard and the process would be killed before echoing),
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//! then echoes its whole argv in one `debug_write` the kernel test asserts on —
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//! proving the kernel-built System V entry stack (argc, argv pointers,
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//! NUL-terminated strings) and the runtime's parsing of it, end to end.
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const runtime = @import("runtime");
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/// Recurse with a real frame each level: `depth` levels of ~0.5 KiB, touched
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/// through a volatile pointer so no optimiser can flatten the frames away.
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fn burnStack(depth: usize) u8 {
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var frame: [512]u8 = undefined;
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const touch: *volatile [512]u8 = &frame;
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touch[0] = @truncate(depth);
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touch[511] = touch[0];
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if (depth == 0) return touch[511];
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return touch[0] +% burnStack(depth - 1);
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}
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pub fn main() void {
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if (runtime.argumentCount() <= 1) {
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// First instance: spawn the second with real arguments, then exit.
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_ = runtime.system.spawnWithArguments("args-echo", &.{ "alpha", "beta-42" });
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return;
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}
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// ~16 x 0.5 KiB frames: comfortably past one page, well inside the 32 KiB stack.
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_ = burnStack(16);
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// Second instance: echo "args: <argv0> <argv1> ..." for the test to match.
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var buffer: [128]u8 = undefined;
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const prefix = "args:";
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@memcpy(buffer[0..prefix.len], prefix);
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var len: usize = prefix.len;
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for (0..runtime.argumentCount()) |i| {
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const argument = runtime.argument(i);
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if (len + 1 + argument.len + 1 > buffer.len) break;
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buffer[len] = ' ';
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len += 1;
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@memcpy(buffer[len..][0..argument.len], argument);
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len += argument.len;
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}
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buffer[len] = '\n';
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len += 1;
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_ = runtime.system.write(buffer[0..len]);
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}
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pub const panic = runtime.panic;
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comptime {
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_ = &runtime.start._start; // pull the runtime entry shim into the image
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}
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