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Remove workaround for qemu 1.4.x and 1.5.x. 

These releases are now 10 years old and are no longer a concern.
This commit is contained in:
Jonas 'Sortie' Termansen 2023-07-08 11:59:11 +02:00
parent e933eb5a1c
commit ffc1b02b94
1 changed files with 0 additions and 27 deletions
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27
kernel/kernel.cpp
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@ -200,33 +200,6 @@ extern "C" void KernelInit(unsigned long magic, multiboot_info_t* bootinfo_p)
// Display the logo.
Log::PrintF("\e[37;41m\e[2J");
Log::Center(BRAND_LOGO);
#if defined(__x86_64__)
// TODO: Remove this hack when qemu 1.4.x and 1.5.0 are obsolete.
// Verify that we are not running under a buggy qemu where the instruction
// movl (%eax), %esi is misinterpreted (amongst others). In this case it
// will try to access the memory at [bx + si]. We'll make sure that eax
// points to a variable on the stack that has another value than at bx + si,
// and if the values compare equal using the buggy instruction, we panic.
uint32_t intended_variable; // rax will point to here.
uint32_t is_buggy_qemu;
asm ("movq $0x1000, %%rbx\n" /* access 32-bit value at 0x1000 */
"movl (%%rbx), %%esi\n"
"subl $1, %%esi\n" /* change the 32-bit value */
"movl %%esi, (%%rax)\n" /* store the new value in intended_variable */
"movq $0x0, %%rsi\n" /* make rsi zero, so bx + si points to 0x1000 */
"movl (%%eax), %%esi\n" /* do the perhaps-buggy memory access */
"movl (%%rax), %%ebx\n" /* do a working memory access */
"movl %%ebx, %0\n" /* load the desired value into is_buggy_qemu */
"subl %%esi, %0\n" /* subtract the possibly incorrect value. */
: "=r"(is_buggy_qemu)
: "a"(&intended_variable)
: "rsi", "rbx");
if ( is_buggy_qemu )
Panic("You are running a buggy version of qemu. The 1.4.x and 1.5.0 "
"releases are known to execute some instructions incorrectly on "
"x86_64 without KVM. You have three options: 1) Enable KVM 2) "
"Use a 32-bit OS 3) Use another version of qemu.");
#endif
char* cmdline = NULL;
if ( bootinfo->flags & MULTIBOOT_INFO_CMDLINE && bootinfo->cmdline )