A simple shell script to tell if your Linux installation is vulnerable against the 3 "speculative execution" CVEs:

CVE-2017-5753 bounds check bypass (Spectre Variant 1)

• Impact: Kernel & all software
• Mitigation: recompile software and kernel with a modified compiler that introduces the LFENCE opcode at the proper positions in the resulting code
• Performance impact of the mitigation: negligible

CVE-2017-5715: branch target injection (Spectre Variant 2)

• Impact: Kernel
• Mitigation 1: new opcode via microcode update that should be used by up to date compilers to protect the BTB (by flushing indirect branch predictors)
• Mitigation 2: introducing "retpoline" into compilers, and recompile software/OS with it
• Performance impact of the mitigation: high for mitigation 1, medium for mitigation 2, depending on your CPU

CVE-2017-5754: rogue data cache load (Meltdown)

• Impact: Kernel
• Mitigation: updated kernel (with PTI/KPTI patches), updating the kernel is enough
• Performance impact of the mitigation: low to medium

Example of the output of the script:

$ sudo ./spectre-meltdown-checker.sh
 Spectre and Meltdown mitigation detection tool v0.09
 
 CVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'
 * Kernel compiled with LFENCE opcode inserted at the proper places:  NO  (only 38 opcodes found, should be >= 60)
 > STATUS:  VULNERABLE
 
 CVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'
 * Mitigation 1
 *   Hardware (CPU microcode) support for mitigation:  NO
 *   Kernel support for IBRS:  NO
 *   IBRS enabled for Kernel space:  NO
 *   IBRS enabled for User space:  NO
 * Mitigation 2
 *   Kernel compiled with retpolines:  NO
 > STATUS:  VULNERABLE  (IBRS hardware + kernel support OR kernel with retpolines are needed to mitigate the vulnerability)
 
 CVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'
 * Kernel supports Page Table Isolation (PTI):  YES
 * PTI enabled and active:  YES
 > STATUS:  NOT VULNERABLE  (PTI mitigates the vulnerability)