1 files changed, 448 insertions, 0 deletions
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
new file mode 100644
index 0000000..0559fe0
--- /dev/null
+++ b/arch/powerpc/lib/code-patching.c
@@ -0,0 +1,448 @@
+/*
+ *  Copyright 2008 Michael Ellerman, IBM Corporation.
+ *
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/vmalloc.h>
+#include <linux/init.h>
+#include <asm/page.h>
+#include <asm/code-patching.h>
+
+
+void patch_instruction(unsigned int *addr, unsigned int instr)
+{
+	*addr = instr;
+	asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" : : "r" (addr));
+}
+
+void patch_branch(unsigned int *addr, unsigned long target, int flags)
+{
+	patch_instruction(addr, create_branch(addr, target, flags));
+}
+
+unsigned int create_branch(const unsigned int *addr,
+			   unsigned long target, int flags)
+{
+	unsigned int instruction;
+	long offset;
+
+	offset = target;
+	if (! (flags & BRANCH_ABSOLUTE))
+		offset = offset - (unsigned long)addr;
+
+	/* Check we can represent the target in the instruction format */
+	if (offset < -0x2000000 || offset > 0x1fffffc || offset & 0x3)
+		return 0;
+
+	/* Mask out the flags and target, so they don't step on each other. */
+	instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
+
+	return instruction;
+}
+
+unsigned int create_cond_branch(const unsigned int *addr,
+				unsigned long target, int flags)
+{
+	unsigned int instruction;
+	long offset;
+
+	offset = target;
+	if (! (flags & BRANCH_ABSOLUTE))
+		offset = offset - (unsigned long)addr;
+
+	/* Check we can represent the target in the instruction format */
+	if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
+		return 0;
+
+	/* Mask out the flags and target, so they don't step on each other. */
+	instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
+
+	return instruction;
+}
+
+static unsigned int branch_opcode(unsigned int instr)
+{
+	return (instr >> 26) & 0x3F;
+}
+
+static int instr_is_branch_iform(unsigned int instr)
+{
+	return branch_opcode(instr) == 18;
+}
+
+static int instr_is_branch_bform(unsigned int instr)
+{
+	return branch_opcode(instr) == 16;
+}
+
+int instr_is_relative_branch(unsigned int instr)
+{
+	if (instr & BRANCH_ABSOLUTE)
+		return 0;
+
+	return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
+}
+
+static unsigned long branch_iform_target(const unsigned int *instr)
+{
+	signed long imm;
+
+	imm = *instr & 0x3FFFFFC;
+
+	/* If the top bit of the immediate value is set this is negative */
+	if (imm & 0x2000000)
+		imm -= 0x4000000;
+
+	if ((*instr & BRANCH_ABSOLUTE) == 0)
+		imm += (unsigned long)instr;
+
+	return (unsigned long)imm;
+}
+
+static unsigned long branch_bform_target(const unsigned int *instr)
+{
+	signed long imm;
+
+	imm = *instr & 0xFFFC;
+
+	/* If the top bit of the immediate value is set this is negative */
+	if (imm & 0x8000)
+		imm -= 0x10000;
+
+	if ((*instr & BRANCH_ABSOLUTE) == 0)
+		imm += (unsigned long)instr;
+
+	return (unsigned long)imm;
+}
+
+unsigned long branch_target(const unsigned int *instr)
+{
+	if (instr_is_branch_iform(*instr))
+		return branch_iform_target(instr);
+	else if (instr_is_branch_bform(*instr))
+		return branch_bform_target(instr);
+
+	return 0;
+}
+
+int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
+{
+	if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
+		return branch_target(instr) == addr;
+
+	return 0;
+}
+
+unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
+{
+	unsigned long target;
+
+	target = branch_target(src);
+
+	if (instr_is_branch_iform(*src))
+		return create_branch(dest, target, *src);
+	else if (instr_is_branch_bform(*src))
+		return create_cond_branch(dest, target, *src);
+
+	return 0;
+}
+
+
+#ifdef CONFIG_CODE_PATCHING_SELFTEST
+
+static void __init test_trampoline(void)
+{
+	asm ("nop;\n");
+}
+
+#define check(x)	\
+	if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);
+
+static void __init test_branch_iform(void)
+{
+	unsigned int instr;
+	unsigned long addr;
+
+	addr = (unsigned long)&instr;
+
+	/* The simplest case, branch to self, no flags */
+	check(instr_is_branch_iform(0x48000000));
+	/* All bits of target set, and flags */
+	check(instr_is_branch_iform(0x4bffffff));
+	/* High bit of opcode set, which is wrong */
+	check(!instr_is_branch_iform(0xcbffffff));
+	/* Middle bits of opcode set, which is wrong */
+	check(!instr_is_branch_iform(0x7bffffff));
+
+	/* Simplest case, branch to self with link */
+	check(instr_is_branch_iform(0x48000001));
+	/* All bits of targets set */
+	check(instr_is_branch_iform(0x4bfffffd));
+	/* Some bits of targets set */
+	check(instr_is_branch_iform(0x4bff00fd));
+	/* Must be a valid branch to start with */
+	check(!instr_is_branch_iform(0x7bfffffd));
+
+	/* Absolute branch to 0x100 */
+	instr = 0x48000103;
+	check(instr_is_branch_to_addr(&instr, 0x100));
+	/* Absolute branch to 0x420fc */
+	instr = 0x480420ff;
+	check(instr_is_branch_to_addr(&instr, 0x420fc));
+	/* Maximum positive relative branch, + 20MB - 4B */
+	instr = 0x49fffffc;
+	check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
+	/* Smallest negative relative branch, - 4B */
+	instr = 0x4bfffffc;
+	check(instr_is_branch_to_addr(&instr, addr - 4));
+	/* Largest negative relative branch, - 32 MB */
+	instr = 0x4a000000;
+	check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
+
+	/* Branch to self, with link */
+	instr = create_branch(&instr, addr, BRANCH_SET_LINK);
+	check(instr_is_branch_to_addr(&instr, addr));
+
+	/* Branch to self - 0x100, with link */
+	instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
+	check(instr_is_branch_to_addr(&instr, addr - 0x100));
+
+	/* Branch to self + 0x100, no link */
+	instr = create_branch(&instr, addr + 0x100, 0);
+	check(instr_is_branch_to_addr(&instr, addr + 0x100));
+
+	/* Maximum relative negative offset, - 32 MB */
+	instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
+	check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
+
+	/* Out of range relative negative offset, - 32 MB + 4*/
+	instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
+	check(instr == 0);
+
+	/* Out of range relative positive offset, + 32 MB */
+	instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
+	check(instr == 0);
+
+	/* Unaligned target */
+	instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
+	check(instr == 0);
+
+	/* Check flags are masked correctly */
+	instr = create_branch(&instr, addr, 0xFFFFFFFC);
+	check(instr_is_branch_to_addr(&instr, addr));
+	check(instr == 0x48000000);
+}
+
+static void __init test_create_function_call(void)
+{
+	unsigned int *iptr;
+	unsigned long dest;
+
+	/* Check we can create a function call */
+	iptr = (unsigned int *)ppc_function_entry(test_trampoline);
+	dest = ppc_function_entry(test_create_function_call);
+	patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
+	check(instr_is_branch_to_addr(iptr, dest));
+}
+
+static void __init test_branch_bform(void)
+{
+	unsigned long addr;
+	unsigned int *iptr, instr, flags;
+
+	iptr = &instr;
+	addr = (unsigned long)iptr;
+
+	/* The simplest case, branch to self, no flags */
+	check(instr_is_branch_bform(0x40000000));
+	/* All bits of target set, and flags */
+	check(instr_is_branch_bform(0x43ffffff));
+	/* High bit of opcode set, which is wrong */
+	check(!instr_is_branch_bform(0xc3ffffff));
+	/* Middle bits of opcode set, which is wrong */
+	check(!instr_is_branch_bform(0x7bffffff));
+
+	/* Absolute conditional branch to 0x100 */
+	instr = 0x43ff0103;
+	check(instr_is_branch_to_addr(&instr, 0x100));
+	/* Absolute conditional branch to 0x20fc */
+	instr = 0x43ff20ff;
+	check(instr_is_branch_to_addr(&instr, 0x20fc));
+	/* Maximum positive relative conditional branch, + 32 KB - 4B */
+	instr = 0x43ff7ffc;
+	check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
+	/* Smallest negative relative conditional branch, - 4B */
+	instr = 0x43fffffc;
+	check(instr_is_branch_to_addr(&instr, addr - 4));
+	/* Largest negative relative conditional branch, - 32 KB */
+	instr = 0x43ff8000;
+	check(instr_is_branch_to_addr(&instr, addr - 0x8000));
+
+	/* All condition code bits set & link */
+	flags = 0x3ff000 | BRANCH_SET_LINK;
+
+	/* Branch to self */
+	instr = create_cond_branch(iptr, addr, flags);
+	check(instr_is_branch_to_addr(&instr, addr));
+
+	/* Branch to self - 0x100 */
+	instr = create_cond_branch(iptr, addr - 0x100, flags);
+	check(instr_is_branch_to_addr(&instr, addr - 0x100));
+
+	/* Branch to self + 0x100 */
+	instr = create_cond_branch(iptr, addr + 0x100, flags);
+	check(instr_is_branch_to_addr(&instr, addr + 0x100));
+
+	/* Maximum relative negative offset, - 32 KB */
+	instr = create_cond_branch(iptr, addr - 0x8000, flags);
+	check(instr_is_branch_to_addr(&instr, addr - 0x8000));
+
+	/* Out of range relative negative offset, - 32 KB + 4*/
+	instr = create_cond_branch(iptr, addr - 0x8004, flags);
+	check(instr == 0);
+
+	/* Out of range relative positive offset, + 32 KB */
+	instr = create_cond_branch(iptr, addr + 0x8000, flags);
+	check(instr == 0);
+
+	/* Unaligned target */
+	instr = create_cond_branch(iptr, addr + 3, flags);
+	check(instr == 0);
+
+	/* Check flags are masked correctly */
+	instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
+	check(instr_is_branch_to_addr(&instr, addr));
+	check(instr == 0x43FF0000);
+}
+
+static void __init test_translate_branch(void)
+{
+	unsigned long addr;
+	unsigned int *p, *q;
+	void *buf;
+
+	buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
+	check(buf);
+	if (!buf)
+		return;
+
+	/* Simple case, branch to self moved a little */
+	p = buf;
+	addr = (unsigned long)p;
+	patch_branch(p, addr, 0);
+	check(instr_is_branch_to_addr(p, addr));
+	q = p + 1;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Maximum negative case, move b . to addr + 32 MB */
+	p = buf;
+	addr = (unsigned long)p;
+	patch_branch(p, addr, 0);
+	q = buf + 0x2000000;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+	check(*q == 0x4a000000);
+
+	/* Maximum positive case, move x to x - 32 MB + 4 */
+	p = buf + 0x2000000;
+	addr = (unsigned long)p;
+	patch_branch(p, addr, 0);
+	q = buf + 4;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+	check(*q == 0x49fffffc);
+
+	/* Jump to x + 16 MB moved to x + 20 MB */
+	p = buf;
+	addr = 0x1000000 + (unsigned long)buf;
+	patch_branch(p, addr, BRANCH_SET_LINK);
+	q = buf + 0x1400000;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Jump to x + 16 MB moved to x - 16 MB + 4 */
+	p = buf + 0x1000000;
+	addr = 0x2000000 + (unsigned long)buf;
+	patch_branch(p, addr, 0);
+	q = buf + 4;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+
+
+	/* Conditional branch tests */
+
+	/* Simple case, branch to self moved a little */
+	p = buf;
+	addr = (unsigned long)p;
+	patch_instruction(p, create_cond_branch(p, addr, 0));
+	check(instr_is_branch_to_addr(p, addr));
+	q = p + 1;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Maximum negative case, move b . to addr + 32 KB */
+	p = buf;
+	addr = (unsigned long)p;
+	patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
+	q = buf + 0x8000;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+	check(*q == 0x43ff8000);
+
+	/* Maximum positive case, move x to x - 32 KB + 4 */
+	p = buf + 0x8000;
+	addr = (unsigned long)p;
+	patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
+	q = buf + 4;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+	check(*q == 0x43ff7ffc);
+
+	/* Jump to x + 12 KB moved to x + 20 KB */
+	p = buf;
+	addr = 0x3000 + (unsigned long)buf;
+	patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
+	q = buf + 0x5000;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Jump to x + 8 KB moved to x - 8 KB + 4 */
+	p = buf + 0x2000;
+	addr = 0x4000 + (unsigned long)buf;
+	patch_instruction(p, create_cond_branch(p, addr, 0));
+	q = buf + 4;
+	patch_instruction(q, translate_branch(q, p));
+	check(instr_is_branch_to_addr(p, addr));
+	check(instr_is_branch_to_addr(q, addr));
+
+	/* Free the buffer we were using */
+	vfree(buf);
+}
+
+static int __init test_code_patching(void)
+{
+	printk(KERN_DEBUG "Running code patching self-tests ...\n");
+
+	test_branch_iform();
+	test_branch_bform();
+	test_create_function_call();
+	test_translate_branch();
+
+	return 0;
+}
+late_initcall(test_code_patching);
+
+#endif /* CONFIG_CODE_PATCHING_SELFTEST */