[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 <paulus@samba.org>
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bb63ab1351
Коммит
1c9bb1a01a
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@ -835,11 +835,21 @@ long sys_swapcontext(struct ucontext __user *old_ctx,
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return -EINVAL;
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if (old_ctx != NULL) {
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struct mcontext __user *mctx;
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/*
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* old_ctx might not be 16-byte aligned, in which
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* case old_ctx->uc_mcontext won't be either.
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* Because we have the old_ctx->uc_pad2 field
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* before old_ctx->uc_mcontext, we need to round down
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* from &old_ctx->uc_mcontext to a 16-byte boundary.
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*/
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mctx = (struct mcontext __user *)
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((unsigned long) &old_ctx->uc_mcontext & ~0xfUL);
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if (!access_ok(VERIFY_WRITE, old_ctx, sizeof(*old_ctx))
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|| save_user_regs(regs, &old_ctx->uc_mcontext, 0)
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|| save_user_regs(regs, mctx, 0)
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|| put_sigset_t(&old_ctx->uc_sigmask, ¤t->blocked)
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|| __put_user(to_user_ptr(&old_ctx->uc_mcontext),
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&old_ctx->uc_regs))
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|| __put_user(to_user_ptr(mctx), &old_ctx->uc_regs))
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return -EFAULT;
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}
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if (new_ctx == NULL)
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