projects/linux·commit 1c9bb1a0

[POWERPC] Fix register save area alignment for swapcontext syscall

1c9bb1a0 · Paul Mackerras <[email protected]> · 2006-12-20 13:57:06 +11:00

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]>
Commit
1c9bb1a01ac1bc92a0d98cf3e40a7922ee684dc0
Parents
bb63ab13

Changes

1 files changed · +13 −3

FileStatusAddDelContent
arch/powerpc/kernel/signal_32.cmodified+13−3View file

arch/powerpc/kernel/signal_32.c

View file
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, &current->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)