powerpc: Add new code patching routines

This commit adds some new routines for patching code, which will be used
in a following commit.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 107 insertions, 0 deletions

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 430f4c1..27957c4 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -41,3 +41,110 @@ unsigned int create_branch(const unsigned int *addr,
 
 	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;
+}