Bootstage Runtime Patched Conditionals

include/bootstage_condition.h View source View on GitHub

Structs

bootstage_condition_entry

struct bootstage_condition_entry (4 fields) source

§ void *code

§ void *target

§ enum bootstage_condition cond

§ enum bootstage stage

Enums

bootstage_condition

enum bootstage_condition (5 variants) source

§ BOOTSTAGE_CONDITION_EQ

§ BOOTSTAGE_CONDITION_LE

§ BOOTSTAGE_CONDITION_LT

§ BOOTSTAGE_CONDITION_GE

§ BOOTSTAGE_CONDITION_GT

Macros

BOOTSTAGE_COND

#define BOOTSTAGE_COND(cond, stage)

source

WARN

stage == BOOTSTAGE_EARLY_FB DOES NOT WORK, because at FB we don’t have the kernel mapping in our control, and we can’t write to it then

NOTE

in theory, we could walk the early page tables and change perms, but this is tricky, and unless I have a super-hot-path that checks EARLY_FB, I don’t see this as super useful

Expansion

#define BOOTSTAGE_COND(cond, stage) \
    ({ \
        __label__ l_yes, l_done; \
        bool _taken = false; \
        asm goto("1:\n\t" \
                 ".byte 0xe9\n\t" \
                 ".long %l[l_yes] - (1b + 5)\n\t" \
                 ".pushsection .kernel_bootstage_condition_entries,\"aw\"\n\t" \
                 ".balign 8\n\t" \
                 ".quad 1b\n\t" \
                 ".quad %l[l_yes]\n\t" \
                 ".long %c[op]\n\t" \
                 ".long %c[stg]\n\t" \
                 ".popsection\n\t" \
                 : \
                 : [op] "i"(cond), [stg] "i"(stage) \
                 : \
                 : l_yes); \
        goto l_done; \
    l_yes: \
        _taken = true; \
    l_done: \
        _taken; \
    })

BOOTSTAGE_IF_EQ

#define BOOTSTAGE_IF_EQ(stage)

source

Expansion

#define BOOTSTAGE_IF_EQ(stage) \
    if (BOOTSTAGE_COND(BOOTSTAGE_CONDITION_EQ, stage))

BOOTSTAGE_IF_LE

#define BOOTSTAGE_IF_LE(stage)

source

Expansion

#define BOOTSTAGE_IF_LE(stage) \
    if (BOOTSTAGE_COND(BOOTSTAGE_CONDITION_LE, stage))

BOOTSTAGE_IF_LT

#define BOOTSTAGE_IF_LT(stage)

source

Expansion

#define BOOTSTAGE_IF_LT(stage) \
    if (BOOTSTAGE_COND(BOOTSTAGE_CONDITION_LT, stage))

BOOTSTAGE_IF_GE

#define BOOTSTAGE_IF_GE(stage)

source

Expansion

#define BOOTSTAGE_IF_GE(stage) \
    if (BOOTSTAGE_COND(BOOTSTAGE_CONDITION_GE, stage))

BOOTSTAGE_IF_GT

#define BOOTSTAGE_IF_GT(stage)

source

Expansion

#define BOOTSTAGE_IF_GT(stage) \
    if (BOOTSTAGE_COND(BOOTSTAGE_CONDITION_GT, stage))