On 11/5/24 13:37, H. Peter Anvin wrote:
What is the point of writing this code in assembly in the first place? A
much more logical thing to do is to just push the registers you haven't
pushed already onto the stack and call a C function to do the actual
dumping? It isn't like it is in any shape, way or form performance
critical.
arch/x86/boot/compressed/misc.c has some code that you can crib, both
for writing to a text screen (not that useful anymore with EFI
framebuffers) and serial port. If you factor it a little bit then you
can probably even share the code directly.
(__putstr perhaps should have a __putchar() factored out of it?)
Then you can just do the obvious (have your assembly stub point %rdi to
the base of the register dump; set the frame order to whatever you'd
like, except rip/err/exc, or reverse the order if you prefer by changing
the loop):
static inline __noreturn void die(void)
{
while (1)
asm volatile("hlt");
}
void dump_register_frame(const unsigned long frame[])
{
static const char regnames[][5] = {
"rax:", "rcx:", "rdx:", "rbx:",
"rsp:", "rbp:", "rsi:", "rdi:",
"r8: ", "r9: ", "r10:", "r11:",
"r12:", "r13:", "r14:", "r15:",
"cr2:", "Exc:", "Err:", "rip:"
};
for (size_t i = 0; i < ARRAY_SIZE(regnames); i++) {
__putstr(regnames[i]);
__puthex(frame[i]);
__putstr("\n");
}
/* Only return from int3 */
if (frame[17] != 3)
die();
}
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