Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=1c9bb1a01ac1bc92a0d98cf3e40a7922ee684dc0
Commit: 1c9bb1a01ac1bc92a0d98cf3e40a7922ee684dc0
Parent: bb63ab13515951f4d09b16c9e8bd6e50b0f20d1e
Author: Paul Mackerras <[EMAIL PROTECTED]>
AuthorDate: Wed Dec 20 13:57:06 2006 +1100
Committer: Paul Mackerras <[EMAIL PROTECTED]>
CommitDate: Wed Dec 20 16:37:49 2006 +1100
[POWERPC] Fix register save area alignment for swapcontext syscall
For 32-bit processes, the getcontext side of the swapcontext system
call (i.e. the saving of the context when the first argument is
non-NULL) has to set the ctx->uc_mcontext.uc_regs pointer to the place
where it saves the registers. Which it does, but it doesn't ensure
that the pointer is 16-byte aligned. 16-byte alignment is needed
because the Altivec/VMX registers are saved in there, and they need to
be on a 16-byte boundary.
This fixes it by ensuring the appropriate alignment of the pointer.
This issue was pointed out by Jakub Jelinek.
Signed-off-by: Paul Mackerras <[EMAIL PROTECTED]>
---
arch/powerpc/kernel/signal_32.c | 16 +++++++++++++---
1 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index e4ebe1a..6b405a3 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -835,11 +835,21 @@ long sys_swapcontext(struct ucontext __user *old_ctx,
return -EINVAL;
if (old_ctx != NULL) {
+ struct mcontext __user *mctx;
+
+ /*
+ * old_ctx might not be 16-byte aligned, in which
+ * case old_ctx->uc_mcontext won't be either.
+ * Because we have the old_ctx->uc_pad2 field
+ * before old_ctx->uc_mcontext, we need to round down
+ * from &old_ctx->uc_mcontext to a 16-byte boundary.
+ */
+ mctx = (struct mcontext __user *)
+ ((unsigned long) &old_ctx->uc_mcontext & ~0xfUL);
if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
- || save_user_regs(regs, &old_ctx->uc_mcontext, 0)
+ || save_user_regs(regs, mctx, 0)
|| put_sigset_t(&old_ctx->uc_sigmask, ¤t->blocked)
- || __put_user(to_user_ptr(&old_ctx->uc_mcontext),
- &old_ctx->uc_regs))
+ || __put_user(to_user_ptr(mctx), &old_ctx->uc_regs))
return -EFAULT;
}
if (new_ctx == NULL)
-
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