how to get goroutine id with ebpf

I use cilium ebpf pakage to write a ebpf program for getting the goroutine id.
but failed. my uprobe.c like this :
I think the key problem is that golang struct g trans to goroutine.h is wrong. can anyone help?

uprobe.c

SEC("uprobe/runtime.newproc1")
int uprobe_runtime_newproc1(struct pt_regs *ctx) {
	u32 key     = 2;
	u64 initval = 1, *valp;

	valp = bpf_map_lookup_elem(&uprobe_map, &key);
	if (!valp) {
		bpf_map_update_elem(&uprobe_map, &key, &initval, BPF_ANY);
		return 0;
	}
	__sync_fetch_and_add(valp, 1);

	struct g* goroutine_struct = (void *)PT_REGS_PARM4(ctx);

    // retrieve output parameter
    s64 goid = 0;
    bpf_probe_read(&goid, sizeof(goid), &goroutine_struct->goid);

    bpf_printk("bpf_printk bpf_probe_read goroutine_struct->goid: %lld", goid);


    struct g gs;
    bpf_probe_read(&gs, sizeof(gs), (void *)PT_REGS_PARM4(ctx));
    bpf_printk("bpf_printk bpf_probe_read goroutine_struct.goid: %lld", gs.goid);

    // test
    void* ptr = (void *)PT_REGS_PARM4(ctx);
    s64 goid2 = 0;
    bpf_probe_read(&goid2, sizeof(goid2), (void *)(ptr+152));
    bpf_printk("bpf_printk bpf_probe_read goid2: %lld", goid2);

	return 0;
}

goroutine.h

#include "common.h"



struct stack  {
	u64 lo;
	u64 hi;
};

struct gobuf  {
	u64 sp;
	u64 pc;
	u64 g;
	u64 ctxt;
	u64 ret;
	u64 lr;
	u64 bp;
};


/*
go version go1.17.2 linux/amd64

type stack struct {
	lo uintptr
	hi uintptr
}

type gobuf struct {
	sp   uintptr
	pc   uintptr
	g    uintptr
	ctxt uintptr
	ret  uintptr
	lr   uintptr
	bp   uintptr
}

type g struct {	
	stack       stack   // offset known to runtime/cgo
	stackguard0 uintptr // offset known to liblink
	stackguard1 uintptr // offset known to liblink

	_panic    *_panic // innermost panic - offset known to liblink
	_defer    *_defer // innermost defer
	m         *m      // current m; offset known to arm liblink
	sched     gobuf
	syscallsp uintptr // if status==Gsyscall, syscallsp = sched.sp to use during gc
	syscallpc uintptr // if status==Gsyscall, syscallpc = sched.pc to use during gc
	stktopsp  uintptr // expected sp at top of stack, to check in traceback
	
	param        unsafe.Pointer
	atomicstatus uint32
	stackLock    uint32 // sigprof/scang lock; TODO: fold in to atomicstatus
	goid         int64
}

*/
struct g {
	struct stack stack;
	u64 stackguard0;
	u64 stackguard1;

	u64 _panic;
	u64 _defer;
	u64 m;
	struct gobuf sched ;
	u64 syscallsp;
	u64 syscallpc;
	u64 stktopsp;
	u64 param;
	u32 atomicstatus;
	u32 stackLock;
	s64 goid;          // Here it is!
};

When I run my program , cat /sys/kernel/debug/tracing/trace_pipe output like this , get the wrong go id:

<...>-1336127 [000] d... 20113210.986990: bpf_trace_printk: bpf_printk bpf_probe_read goroutine_struct->goid: 4938558469562467144
<...>-1336127 [000] d... 20113210.986998: bpf_trace_printk: bpf_printk bpf_probe_read goroutine_struct.goid: 4938558469562467144
<...>-1336127 [000] d... 20113210.986998: bpf_trace_printk: bpf_printk bpf_probe_read goid2: 4938558469562467144
Blockquote

I found a solution:

1. my golang version is 1.17.2, amd64. and the amd64 architecture uses the following sequence of 9 registers for integer arguments and results:
   RAX, RBX, RCX, RDI, RSI, R8, R9, R10, R11

2. runtime.newproc1 which in go 1.17.2 has 5 args. callergp *g is the 4th. when I gdb my userspace program, it use rdi register to save ptr addr of callergp *g.
   so use PT_REGS_PARM1 is the right way. because (#define PT_REGS_PARM1(x) ((x)->rdi))

3. after all, the code like this :

    SEC("uprobe/runtime.newproc1")
    int uprobe_runtime_newproc1(struct pt_regs *ctx) {
    	u32 key     = 2;
    	u64 initval = 1, *valp;
    
    	valp = bpf_map_lookup_elem(&uprobe_map, &key);
    	if (!valp) {
    		bpf_map_update_elem(&uprobe_map, &key, &initval, BPF_ANY);
    		return 0;
    	}
    	__sync_fetch_and_add(valp, 1);
    
        // retrieve output parameter
        struct g gs;
        bpf_probe_read(&gs, sizeof(gs), (void *)PT_REGS_PARM1(ctx));
        bpf_printk("uprobe_runtime_newproc1 bpf_printk bpf_probe_read goroutine_struct.goid: %lld", gs.goid);
    
    	return 0;
    }