x86 asm: move rotation and bit instructoins in from x86-assembly-cheat

2026-01-29 13:04:27 +01:00 · 2019-06-16 00:00:03 +00:00
parent 89084d2332
commit 658ac53d0f
10 changed files with 313 additions and 0 deletions
--- a/userland/arch/x86_64/rcl.S
+++ b/userland/arch/x86_64/rcl.S
@@ -0,0 +1,38 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#x86-shift-and-rotate-instructions */
+
+#include <lkmc.h>
+
+LKMC_PROLOGUE
+    mov $0x81, %r12
+    clc
+
+    rcl $1, %r12b
+    /* We'll have to save and restore flags across our asserts!
+        * 2x PUSHF to maintain 16-bit stack alignment.
+        * https://github.com/cirosantilli/linux-kernel-module-cheat#x86_64-calling-convention
+        */
+    pushf
+    pushf
+    LKMC_ASSERT(jc)
+    LKMC_ASSERT_EQ(%r12, $2)
+
+    popf
+    rcl $1, %r12b
+    pushf
+    LKMC_ASSERT(jnc)
+    LKMC_ASSERT_EQ(%r12, $5)
+
+    popf
+    rcr $2, %r12b
+    pushf
+    LKMC_ASSERT(jnc)
+    LKMC_ASSERT_EQ(%r12, $0x81)
+
+    popf
+    rcr $1, %r12b
+    pushf
+    LKMC_ASSERT(jc)
+    LKMC_ASSERT_EQ(%r12, $0x40)
+
+    add $16, %rsp
+LKMC_EPILOGUE