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authorMichael Ellerman <michael@ellerman.id.au>2008-06-24 05:32:24 +0400
committerPaul Mackerras <paulus@samba.org>2008-07-01 05:28:19 +0400
commit053a858efa46c9ab86363b271374ec02ad2af753 (patch)
tree21f5a7dd1718d33a38083fc51cdaad054fdbae72 /arch/powerpc/lib
parente7a57273c6407bb6903fbaddec8c2119bf318617 (diff)
downloadlinux-053a858efa46c9ab86363b271374ec02ad2af753.tar.xz
powerpc: Make create_branch() return errors if the branch target is too large
If you pass a target value to create_branch() which is more than 32MB - 4, or - 32MB away from the branch site, then it's impossible to create an immediate branch. The current code doesn't check, which will lead to us creating a branch to somewhere else - which is bad. For code that cares to check we return 0, which is easy to check for, and for code that doesn't at least we'll be creating an illegal instruction, rather than a branch to some random address. Signed-off-by: Michael Ellerman <michael@ellerman.id.au> Acked-by: Kumar Gala <galak@kernel.crashing.org> Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/lib')
-rw-r--r--arch/powerpc/lib/code-patching.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 638dde313cbc..430f4c15d786 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -26,12 +26,18 @@ unsigned int create_branch(const unsigned int *addr,
unsigned long target, int flags)
{
unsigned int instruction;
+ long offset;
+ offset = target;
if (! (flags & BRANCH_ABSOLUTE))
- target = target - (unsigned long)addr;
+ 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) | (target & 0x03FFFFFC);
+ instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
return instruction;
}