diff options
| -rw-r--r-- | arch/x86/kernel/dumpstack.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index ee344030fd0a..666a284116ac 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -72,6 +72,25 @@ static void printk_stack_address(unsigned long address, int reliable, printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address); } +/* + * There are a couple of reasons for the 2/3rd prologue, courtesy of Linus: + * + * In case where we don't have the exact kernel image (which, if we did, we can + * simply disassemble and navigate to the RIP), the purpose of the bigger + * prologue is to have more context and to be able to correlate the code from + * the different toolchains better. + * + * In addition, it helps in recreating the register allocation of the failing + * kernel and thus make sense of the register dump. + * + * What is more, the additional complication of a variable length insn arch like + * x86 warrants having longer byte sequence before rIP so that the disassembler + * can "sync" up properly and find instruction boundaries when decoding the + * opcode bytes. + * + * Thus, the 2/3rds prologue and 64 byte OPCODE_BUFSIZE is just a random + * guesstimate in attempt to achieve all of the above. + */ void show_opcodes(u8 *rip, const char *loglvl) { unsigned int code_prologue = OPCODE_BUFSIZE * 2 / 3; |