pt_buffer_reset_offsets(9)

pt_buffer_reset_offsets(9) 🎀

okay so welcome to this Kernel API Manual page, bestie — we’re talking about pt_buffer_reset_offsets(9), and yes it’s giving “tiny function, very specific job” energy. 💅

🌸 NAME 🌸

pt_buffer_reset_offsets — adjust buffer’s write pointers from aux_head ✨

🦋 SYNOPSIS 🦋

void pt_buffer_reset_offsets (struct pt_buffer *buf , unsigned long head
);

🎀 ARGUMENTS 🎀

• buf — PT buffer. 💖
• head — Write pointer (aux_head) from AUX buffer.

💫 DESCRIPTION 💫

Find the ToPA table and entry corresponding to the given head, and set the buffer’s “current” pointers accordingly. This is done after we have obtained the current aux_head position from a successful call to perf_aux_output_begin, to make sure the hardware is writing to the right place. 🫶

This function modifies buf::{cur,cur_idx,output_off} that will be programmed into PT msrs when the tracing is enabled, and buf::head and buf::data_size, which are used to determine INT and STOP markers’ locations by a subsequent call to pt_buffer_reset_markers. like, that’s the whole little pointer-maintenance moment, and it ate. 🔥

👀 SEE ALSO 👀

Kernel file ./arch/x86/events/intel/pt.c:

• struct topa(9)
• struct topa_page(9)
• topa_alloc(9)
• topa_free(9)
• topa_insert_table(9)
• topa_table_full(9)
• topa_insert_pages(9)
• pt_topa_dump(9)
• pt_buffer_advance(9)
• pt_update_head(9)
• pt_buffer_region(9)
• pt_buffer_region_size(9)
• pt_handle_status(9)
• pt_read_offset(9)
• pt_buffer_reset_markers(9)
• pt_buffer_fini_topa(9)
• pt_buffer_init_topa(9)
• pt_buffer_setup_aux(9)
• pt_buffer_free_aux(9)
• intel_pt_interrupt(9)

later bestie 🫶 — this one’s from source/version ./arch/x86/events/intel, dated October 2026, and it will always be pt_buffer_reset_offsets(9) to me. 💜