Indirect Branch Tracking (IBT) is part of Intel's Control-Flow
Enforcement Technology (CET). IBT is hardware based, forward edge
Control-Flow-Integrity mechanism where any indirect CALL/JMP must target
an ENDBR instruction or suffer #CP.
This commit adds IBT support for fiber:
1. Add endbr32/64 in assembly
2. Inform compiler jump_fcontext may return via indirect branch
Furthermore:
gcc support CET since v8.1 and set it to default since gcc 11. That is,
the ELF header of sapi/cli/php has a property named IBT. However, such
property is lost since PHP8.1 because the assembly introduced by Fiber.
This commit also fixes this.
Closes GH-8339
Signed-off-by: Chen, Hu <hu1.chen@intel.com>
Co-authored-by: Christoph M. Becker <cmbecker69@gmx.de>
