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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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2679f9bd0a
This patch adds Kernel Userspace Access Protection on the 8xx. When a page is RO or RW, it is set RO or RW for Key 0 and NA for Key 1. Up to now, the User group is defined with Key 0 for both User and Supervisor. By changing the group to Key 0 for User and Key 1 for Supervisor, this patch prevents the Kernel from being able to access user data. At exception entry, the kernel saves SPRN_MD_AP in the regs struct, and reapply the protection. At exception exit it restores SPRN_MD_AP with the value saved on exception entry. Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> [mpe: Drop allow_read/write_to/from_user() as they're now in kup.h] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
59 lines
1.3 KiB
C
59 lines
1.3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_POWERPC_KUP_8XX_H_
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#define _ASM_POWERPC_KUP_8XX_H_
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#include <asm/bug.h>
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#ifdef CONFIG_PPC_KUAP
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#ifdef __ASSEMBLY__
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.macro kuap_save_and_lock sp, thread, gpr1, gpr2, gpr3
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lis \gpr2, MD_APG_KUAP@h /* only APG0 and APG1 are used */
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mfspr \gpr1, SPRN_MD_AP
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mtspr SPRN_MD_AP, \gpr2
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stw \gpr1, STACK_REGS_KUAP(\sp)
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.endm
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.macro kuap_restore sp, current, gpr1, gpr2, gpr3
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lwz \gpr1, STACK_REGS_KUAP(\sp)
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mtspr SPRN_MD_AP, \gpr1
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.endm
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.macro kuap_check current, gpr
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#ifdef CONFIG_PPC_KUAP_DEBUG
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mfspr \gpr, SPRN_MD_AP
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rlwinm \gpr, \gpr, 16, 0xffff
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999: twnei \gpr, MD_APG_KUAP@h
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EMIT_BUG_ENTRY 999b, __FILE__, __LINE__, (BUGFLAG_WARNING | BUGFLAG_ONCE)
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#endif
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.endm
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#else /* !__ASSEMBLY__ */
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#include <asm/reg.h>
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static inline void allow_user_access(void __user *to, const void __user *from,
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unsigned long size)
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{
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mtspr(SPRN_MD_AP, MD_APG_INIT);
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}
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static inline void prevent_user_access(void __user *to, const void __user *from,
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unsigned long size)
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{
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mtspr(SPRN_MD_AP, MD_APG_KUAP);
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}
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static inline bool bad_kuap_fault(struct pt_regs *regs, bool is_write)
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{
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return WARN(!((regs->kuap ^ MD_APG_KUAP) & 0xf0000000),
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"Bug: fault blocked by AP register !");
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}
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#endif /* !__ASSEMBLY__ */
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#endif /* CONFIG_PPC_KUAP */
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#endif /* _ASM_POWERPC_KUP_8XX_H_ */
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