Change in coreboot[master]: arch/x86: Add support for catching null deferences through debug regs

[Tim Wawrzynczak (Code Review)]

Attention is currently required from: Robert Zieba, Nico Huber, Raul Rangel, Angel Pons, Arthur Heymans, Tim Wawrzynczak, Kyösti Mälkki.
Tim Wawrzynczak has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/63657 )

Change subject: arch/x86: Add support for catching null deferences through debug regs
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Patch Set 5:

(2 comments)

File src/arch/x86/null_breakpoint.c:

https://review.coreboot.org/c/coreboot/+/63657/comment/d96bb75e_0b723edc 
PS5, Line 12:     if (handle == null_exec_bp) {
            :         printk(BIOS_ERR, "Null instruction execution\n");
            :     }
            :     else {
            : #if ENV_X86_64
            :     printk(BIOS_ERR, "Null dereference at rip: 0x%llx \n", regs->rip);
            : #else
            :     printk(BIOS_ERR, "Null dereference at eip: 0x%x \n", regs->eip);
            : #endif
            :     }
```
if (handle == null_exec_bp) {
    printk(BIOS_ERR, "Null instruction execution\n");
} else {
#if ENV_X86_64
    printk(BIOS_ERR, "Null dereference at rip: 0x%llx \n", regs->rip);
#else
    printk(BIOS_ERR, "Null dereference at eip: 0x%x \n", regs->eip);
#endif
}
```

https://review.coreboot.org/c/coreboot/+/63657/comment/d6efd530_ebb9b1e7 
PS5, Line 29:     if (res != BREAKPOINT_RES_OK) {
            :         printk(BIOS_ERR, "Failed to create NULL dereference breakpoint\n");
            :     }
            : 
            :     res = breakpoint_create_instruction(&null_exec_bp, NULL);
            :     if (res != BREAKPOINT_RES_OK) {
            :         printk(BIOS_ERR, "Failed to create NULL execution breakpoint\n");
            :     }
braces not required for single-statement following an if