Experimental tracepoint support #1084
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rust/kernel/tracepoint.rs
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| if should_trace { | ||
| // TODO: cpu_online(raw_smp_processor_id()) |
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What are the ramifications of not having this? If the CPU is offline, will we hang, or just delay?
| .quad {0} + {1} - . | ||
| .popsection | ||
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| 2: mov {2:e}, 0 |
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Could you show me how to do that?
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options(att_syntax), here is an example:
unsafe fn i32_xadd(v: *mut i32, mut i: i32) -> i32 {
// SAFETY: Per function safety requirement, the address of `v` is valid for "xadd".
unsafe {
asm!(
lock_instr!("xaddl {i:e}, ({v})"),
i = inout(reg) i,
v = in(reg) v,
options(att_syntax, preserves_flags),
);
}
i
}in https://lore.kernel.org/rust-for-linux/[email protected]/
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Kernel developers will prefer that, yeah... :)
Sadly, specifying every single time that may be painful. Perhaps we could have our own asm! that expands to the actual one plus that option, if that is possible, or otherwise it would be nice to have a rustc flag to always use that by default.
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A asm! wrapper should be fairly straightforward. The asm macro deliberately allows multiple options to simplify cases where people want to always add options(att_syntax). See rust-lang/rust#73227.
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Thanks Gary, then we should probably do it soon if we are going to start adding more asm! blocks. I would still like to have a flag (or similar) nevertheless, to avoid extra macros and to match the C compilers.
Darksonn
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Add static_call support by mirroring how C does. When the platform does not support static calls (right now, that means that it is not x86), then the function pointer is loaded from a global and called. Otherwise, we generate a call to a trampoline function, and objtool is used to make these calls patchable at runtime. Signed-off-by: Alice Ryhl <[email protected]>
Add just enough support for static key so that we can use it from tracepoints. Tracepoints rely on `static_key_false` even though it is deprecated, so we add the same functionality to Rust. Signed-off-by: Alice Ryhl <[email protected]>
Make it possible to have Rust code call into tracepoints defined by C code. It is still required that the tracepoint is declared in a C header, and that this header is included in the input to bindgen. Signed-off-by: Alice Ryhl <[email protected]>
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