diff options
Diffstat (limited to 'guest')
| -rw-r--r-- | guest/Makefile | 12 | ||||
| -rw-r--r-- | guest/guest64-msr.S | 91 | ||||
| -rw-r--r-- | guest/guest64.S | 4 |
3 files changed, 100 insertions, 7 deletions
diff --git a/guest/Makefile b/guest/Makefile index 635759a..61d7790 100644 --- a/guest/Makefile +++ b/guest/Makefile @@ -1,14 +1,16 @@ ARCH16 := i8086 ARCH64 := i386:x86-64 -guest: guest16 guest64 -disasm: disasm16 disasm64 +bits = $(word 1, $(subst -, ,$(1))) + +guest: guest16 guest64 guest64-msr +disasm: disasm16 disasm64 disasm64-msr guest%: guest.ld guest%.S - $(CC) $(CFLAGS) -m$* -o $@ -nostdlib -ffreestanding -Wpedantic -Wall -Wextra -Werror -T guest.ld guest$*.S + $(CC) $(CFLAGS) -m$(call bits, $*) -o $@ -nostdlib -ffreestanding -Wpedantic -Wall -Wextra -Werror -T guest.ld guest$*.S disasm%: guest% - objdump -D -b binary -m $(ARCH$*) -M intel $^ + objdump -D -b binary -m $(ARCH$(call bits, $*)) -M intel $^ clean: - $(RM) guest16 guest64 + $(RM) guest16 guest64 guest64-msr diff --git a/guest/guest64-msr.S b/guest/guest64-msr.S new file mode 100644 index 0000000..8e7d4a4 --- /dev/null +++ b/guest/guest64-msr.S @@ -0,0 +1,91 @@ +.intel_syntax noprefix + +// Define a string literal. +.macro defstr name str +\name: + .ascii "\str" +\name\()_len: + .8byte . - \name +.endm + +// Print a string literal. +.macro pstr name + mov dx, 0x42 // Magic IO port for strings. + lea rsi, [rip + \name] // Address of string. + mov rcx, [rip + \name\()_len] // Len of string. + rep outsb // Write ds:rsi to output port rdx. +.endm + +.section .boot, "ax", @progbits + // -- SWAPGS test ----------------------------------------------------------- + + // Setup IA32_GS_BASE. + mov rcx, 0xc0000101 + mov rax, 0xbbbbbbbb + call wrmsr + + // Setup IA32_KERNEL_GS_BASE. + mov rcx, 0xc0000102 + mov rax, 0xaaaaaaaa + call wrmsr + + // Print IA32_GS_BASE. + pstr gsbase + mov rcx, 0xc0000101 + call rdmsr + call pu64 + + // Print IA32_KERNEL_GS_BASE. + pstr kgsbase + mov rcx, 0xc0000102 + call rdmsr + call pu64 + + pstr swapgs + // Swap IA32_GS_BASE and IA32_KERNEL_GS_BASE. + swapgs + + // Print IA32_GS_BASE. + pstr gsbase + mov rcx, 0xc0000101 + call rdmsr + call pu64 + + // Print IA32_KERNEL_GS_BASE. + pstr kgsbase + mov rcx, 0xc0000102 + call rdmsr + call pu64 + + // Trigger `KVM_EXIT_HLT`. + hlt + +// in : ecx address of msr register +// out: rax value of msr register +rdmsr: + rdmsr + shl rdx, 32 + or rax, rdx + ret + +// in: ecx address of msr register +// in: rax value to write into msr register +wrmsr: + mov rdx, rax + shr rdx, 32 + wrmsr + ret + +// in: rax holds 64bit word to be printed +pu64: + xor dx, dx // Port to print values. + out dx, eax // Print lower-half (u32) of rax. + //shr rax, 32 + //out dx, eax // Print upper-half (u32) of rax. + ret + +.section .rodata, "a", @progbits +defstr fsbase, "fsbase: " +defstr gsbase, "gsbase: " +defstr kgsbase, "kernel_gsbase: " +defstr swapgs, "-- swapgs --\n" diff --git a/guest/guest64.S b/guest/guest64.S index 1ca91a5..dc3e986 100644 --- a/guest/guest64.S +++ b/guest/guest64.S @@ -2,7 +2,7 @@ .section .boot, "ax", @progbits // Trigger `KVM_EXIT_IO:KVM_EXIT_IO_OUT` by writing string to output port. - mov rdx, 0x1000 // Output port. + mov rdx, 0x42 // Output port (magic for string fmt). lea rsi, [rip + msg] // Address of string. mov rcx, [rip + msg_len] // Len of string. rep outsb // Write ds:rsi to output port rdx. @@ -30,7 +30,7 @@ .section .rodata, "a", @progbits msg: - .asciz "Hello from Long Mode!\n" + .ascii "Hello from Long Mode!\n" msg_len: .byte .-msg |