On Tue, Jun 10, 2025 at 6:03 PM Steven Rostedt [off-list ref] wrote:
Hi Peter and Ingo,
This is the first patch series of a set that will make it possible to be able
to use SFrames[1] in the Linux kernel. A quick recap of the motivation for
doing this.
Currently the only way to get a user space stack trace from a stack
walk (and not just copying large amount of user stack into the kernel
ring buffer) is to use frame pointers. This has a few issues. The biggest
one is that compiling frame pointers into every application and library
has been shown to cause performance overhead.
Another issue is that the format of the frames may not always be consistent
between different compilers and some architectures (s390) has no defined
format to do a reliable stack walk. The only way to perform user space
profiling on these architectures is to copy the user stack into the kernel
buffer.
SFrames is now supported in gcc binutils and soon will also be supported
by LLVM. SFrames acts more like ORC, and lives in the ELF executable
Is there any upstream PR or discussion for SFrames support in LLVM to
keep track of?
file as its own section. Like ORC it has two tables where the first table
is sorted by instruction pointers (IP) and using the current IP and finding
it's entry in the first table, it will take you to the second table which
will tell you where the return address of the current function is located
and then you can use that address to look it up in the first table to find
the return address of that function, and so on. This performs a user
space stack walk.
[...]