add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/tools/testing/selftests/x86/sigreturn.c
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@@ -1,15 +1,7 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  * sigreturn.c - tests for x86 sigreturn(2) and exit-to-userspace
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  * Copyright (c) 2014-2015 Andrew Lutomirski
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- *
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- * This program is free software; you can redistribute it and/or modify
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- * it under the terms and conditions of the GNU General Public License,
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- * version 2, as published by the Free Software Foundation.
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- *
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- * This program is distributed in the hope it will be useful, but
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- * WITHOUT ANY WARRANTY; without even the implied warranty of
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- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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- * General Public License for more details.
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  *
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  * This is a series of tests that exercises the sigreturn(2) syscall and
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  * the IRET / SYSRET paths in the kernel.
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@@ -459,6 +451,19 @@
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 	ctx->uc_mcontext.gregs[REG_SP] = (unsigned long)0x8badf00d5aadc0deULL;
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 	ctx->uc_mcontext.gregs[REG_CX] = 0;
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+#ifdef __i386__
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+	/*
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+	 * Make sure the kernel doesn't inadvertently use DS or ES-relative
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+	 * accesses in a region where user DS or ES is loaded.
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+	 *
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+	 * Skip this for 64-bit builds because long mode doesn't care about
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+	 * DS and ES and skipping it increases test coverage a little bit,
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+	 * since 64-bit kernels can still run the 32-bit build.
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+	 */
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+	ctx->uc_mcontext.gregs[REG_DS] = 0;
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+	ctx->uc_mcontext.gregs[REG_ES] = 0;
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+#endif
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+
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 	memcpy(&requested_regs, &ctx->uc_mcontext.gregs, sizeof(gregset_t));
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 	requested_regs[REG_CX] = *ssptr(ctx);	/* The asm code does this. */
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