fgraph_retrieve_data(9)

💅 fgraph_retrieve_data — a kernel API manual (yes, the section 9 kind, we're fancy)

okay so bestie, welcome to the fgraph_retrieve_data(9) page — it lives in the Kernel API Manual, and it's genuinely one of the shorter reads in the ftrace cinematic universe, so you can absolutely finish this before your iced coffee melts 🧊✨

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🌸 NAME 🌸

fgraph_retrieve_data — the lil function that goes and gets your data back after you stashed it with fgraph_reserve_data(). it's giving "lost and found but for kernel trace data" 🎀

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✨ SYNOPSIS ✨

void * fgraph_retrieve_data (int idx , int *size_bytes );

that's the whole signature, no cap 💅

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🫶 ARGUMENTS 🫶

• idx — the index of fgraph_array, aka fgraph_ops::idx. it's literally just which slot in the array we're talking about, iykyk.
• size_bytes — a pointer to the retrieved data size. so it hands you back how big the thing is, through a pointer, because of course it does 🫠

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🦋 DESCRIPTION 🦋

okay so this is the main character section, listen up 🌟

you call this from a fgraph_ops retfunc, and its whole job is to retrieve the data that was stored by that same fgraph_ops entryfunc back when the function entered. like, entryfunc stashed it, retfunc comes back and picks it up — the full glow-up-to-glow-down pipeline 💖

in the manual's own exact words: this will retrieve the data that was reserved on the entry of the function that corresponds to the exit of the function that the fgraph_ops retfunc is called on. so entry of func ↔ exit of that same func, and fgraph_retrieve_data is your bridge between the two 🧚

lowkey important: it's meant to be called by a fgraph_ops retfunc. that's the vibe it was designed for, bestie, don't come at it from random places 🙈

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👑 RETURN 👑

it returns the stored data from fgraph_reserve_data that was called by the matching entryfunc for the retfunc you're calling this from. ✨

or — and this is the part where you go 😭 — it returns NULL if there was nothing stored. so like, always vibe check your return value, fr fr. NULL is a real possible outcome, not a personality flaw 💀

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🌈 SEE ALSO 🌈

go read these next, they're all in the kernel file ./kernel/trace/fgraph.c and they're all part of the same friend group 🫶:

• fgraph_reserve_data(9)
• fgraph_get_task_var(9)
• fgraph_retrieve_parent_data(9)
• ftrace_graph_stop(9)
• ftrace_graph_get_ret_stack(9)
• ftrace_graph_top_ret_addr(9)
• ftrace_graph_ret_addr(9)

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and that's the page, bestie! 🎀 this iconic lil number comes from ./kernel/trace and it's dated October 2026 — so yeah, mark your calendar, this manual page is booked and busy 💅🔥 mwah, go trace some functions 💜