Commits on Dec 3, 2024

1. create-diff-object: Create __patchable_function_entries sections …

   The __mcount_loc section contains the addresses of patchable ftrace
   sites which is used by the ftrace infrastructure in the kernel to create
   a list of tracable functions and to know where to patch to enable
   tracing of them.  On some kernel configurations, section is called
   __patchable_function_entries and is generated by the compiler.  Either of
   __mcount_loc or __patchable_function_entries is recognised by the kernel
   but for these configurations, use __patchable_function_entries as it is
   what is expected.
   
   The x86_64 arch is special (of course).  Unlike other arches (ppc64le
   and aarch64) a x86_64 kernel built with -fpatchable-function-entry will
   generate nops AND create rela__patchable_function_entries for functions even
   marked as notrace.  For this arch, always create __mount_loc sections and
   rely on __fentry__ relocations to indicate ftrace call sites.
   
   Note: this patch is a refactoring of original code by Pete Swain
   <swine@google.com> for aarch64.  At the same time, this version squashes
   several follow up commits from him and zimao <zimao@microsoft.com>.  The
   intent is minimize the eventual changeset for aarch64 support now that
   other arches are making use of __patchable_function_entries sections.
   
   Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>

   

   joe-lawrence committed Dec 3, 2024
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