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kernel/arch/s390/kvm/gaccess.h
Nico Boehr e8061f0618 KVM: s390: gaccess: Check if guest address is in memslot 
Previously, access_guest_page() did not check whether the given guest
address is inside of a memslot. This is not a problem, since
kvm_write_guest_page/kvm_read_guest_page return -EFAULT in this case.

However, -EFAULT is also returned when copy_to/from_user fails.

When emulating a guest instruction, the address being outside a memslot
usually means that an addressing exception should be injected into the
guest.

Failure in copy_to/from_user however indicates that something is wrong
in userspace and hence should be handled there.

To be able to distinguish these two cases, return PGM_ADDRESSING in
access_guest_page() when the guest address is outside guest memory. In
access_guest_real(), populate vcpu->arch.pgm.code such that
kvm_s390_inject_prog_cond() can be used in the caller for injecting into
the guest (if applicable).

Since this adds a new return value to access_guest_page(), we need to make
sure that other callers are not confused by the new positive return value.

There are the following users of access_guest_page():
- access_guest_with_key() does the checking itself (in
  guest_range_to_gpas()), so this case should never happen. Even if, the
  handling is set up properly.
- access_guest_real() just passes the return code to its callers, which
  are:
    - read_guest_real() - see below
    - write_guest_real() - see below

There are the following users of read_guest_real():
- ar_translation() in gaccess.c which already returns PGM_*
- setup_apcb10(), setup_apcb00(), setup_apcb11() in vsie.c which always
  return -EFAULT on read_guest_read() nonzero return - no change
- shadow_crycb(), handle_stfle() always present this as validity, this
  could be handled better but doesn't change current behaviour - no change

There are the following users of write_guest_real():
- kvm_s390_store_status_unloaded() always returns -EFAULT on
  write_guest_real() failure.

Fixes: 2293897805 ("KVM: s390: add architecture compliant guest access functions")
Cc: stable@vger.kernel.org
Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/r/20240917151904.74314-2-nrb@linux.ibm.com
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2024-10-10 15:31:55 +02:00

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* access guest memory
*
* Copyright IBM Corp. 2008, 2014
*
* Author(s): Carsten Otte <cotte@de.ibm.com>
*/
#ifndef __KVM_S390_GACCESS_H
#define __KVM_S390_GACCESS_H
#include <linux/compiler.h>
#include <linux/kvm_host.h>
#include <linux/uaccess.h>
#include <linux/ptrace.h>
#include "kvm-s390.h"
/**
* kvm_s390_real_to_abs - convert guest real address to guest absolute address
* @prefix - guest prefix
* @gra - guest real address
*
* Returns the guest absolute address that corresponds to the passed guest real
* address @gra of by applying the given prefix.
*/
static inline unsigned long _kvm_s390_real_to_abs(u32 prefix, unsigned long gra)
{
if (gra < 2 * PAGE_SIZE)
gra += prefix;
else if (gra >= prefix && gra < prefix + 2 * PAGE_SIZE)
gra -= prefix;
return gra;
}
/**
* kvm_s390_real_to_abs - convert guest real address to guest absolute address
* @vcpu - guest virtual cpu
* @gra - guest real address
*
* Returns the guest absolute address that corresponds to the passed guest real
* address @gra of a virtual guest cpu by applying its prefix.
*/
static inline unsigned long kvm_s390_real_to_abs(struct kvm_vcpu *vcpu,
unsigned long gra)
{
return _kvm_s390_real_to_abs(kvm_s390_get_prefix(vcpu), gra);
}
/**
* _kvm_s390_logical_to_effective - convert guest logical to effective address
* @psw: psw of the guest
* @ga: guest logical address
*
* Convert a guest logical address to an effective address by applying the
* rules of the addressing mode defined by bits 31 and 32 of the given PSW
* (extendended/basic addressing mode).
*
* Depending on the addressing mode, the upper 40 bits (24 bit addressing
* mode), 33 bits (31 bit addressing mode) or no bits (64 bit addressing
* mode) of @ga will be zeroed and the remaining bits will be returned.
*/
static inline unsigned long _kvm_s390_logical_to_effective(psw_t *psw,
unsigned long ga)
{
if (psw_bits(*psw).eaba == PSW_BITS_AMODE_64BIT)
return ga;
if (psw_bits(*psw).eaba == PSW_BITS_AMODE_31BIT)
return ga & ((1UL << 31) - 1);
return ga & ((1UL << 24) - 1);
}
/**
* kvm_s390_logical_to_effective - convert guest logical to effective address
* @vcpu: guest virtual cpu
* @ga: guest logical address
*
* Convert a guest vcpu logical address to a guest vcpu effective address by
* applying the rules of the vcpu's addressing mode defined by PSW bits 31
* and 32 (extendended/basic addressing mode).
*
* Depending on the vcpu's addressing mode the upper 40 bits (24 bit addressing
* mode), 33 bits (31 bit addressing mode) or no bits (64 bit addressing mode)
* of @ga will be zeroed and the remaining bits will be returned.
*/
static inline unsigned long kvm_s390_logical_to_effective(struct kvm_vcpu *vcpu,
unsigned long ga)
{
return _kvm_s390_logical_to_effective(&vcpu->arch.sie_block->gpsw, ga);
}
/*
* put_guest_lc, read_guest_lc and write_guest_lc are guest access functions
* which shall only be used to access the lowcore of a vcpu.
* These functions should be used for e.g. interrupt handlers where no
* guest memory access protection facilities, like key or low address
* protection, are applicable.
* At a later point guest vcpu lowcore access should happen via pinned
* prefix pages, so that these pages can be accessed directly via the
* kernel mapping. All of these *_lc functions can be removed then.
*/
/**
* put_guest_lc - write a simple variable to a guest vcpu's lowcore
* @vcpu: virtual cpu
* @x: value to copy to guest
* @gra: vcpu's destination guest real address
*
* Copies a simple value from kernel space to a guest vcpu's lowcore.
* The size of the variable may be 1, 2, 4 or 8 bytes. The destination
* must be located in the vcpu's lowcore. Otherwise the result is undefined.
*
* Returns zero on success or -EFAULT on error.
*
* Note: an error indicates that either the kernel is out of memory or
* the guest memory mapping is broken. In any case the best solution
* would be to terminate the guest.
* It is wrong to inject a guest exception.
*/
#define put_guest_lc(vcpu, x, gra) \
({ \
struct kvm_vcpu *__vcpu = (vcpu); \
__typeof__(*(gra)) __x = (x); \
unsigned long __gpa; \
\
__gpa = (unsigned long)(gra); \
__gpa += kvm_s390_get_prefix(__vcpu); \
kvm_write_guest(__vcpu->kvm, __gpa, &__x, sizeof(__x)); \
})
/**
* write_guest_lc - copy data from kernel space to guest vcpu's lowcore
* @vcpu: virtual cpu
* @gra: vcpu's source guest real address
* @data: source address in kernel space
* @len: number of bytes to copy
*
* Copy data from kernel space to guest vcpu's lowcore. The entire range must
* be located within the vcpu's lowcore, otherwise the result is undefined.
*
* Returns zero on success or -EFAULT on error.
*
* Note: an error indicates that either the kernel is out of memory or
* the guest memory mapping is broken. In any case the best solution
* would be to terminate the guest.
* It is wrong to inject a guest exception.
*/
static inline __must_check
int write_guest_lc(struct kvm_vcpu *vcpu, unsigned long gra, void *data,
unsigned long len)
{
unsigned long gpa = gra + kvm_s390_get_prefix(vcpu);
return kvm_write_guest(vcpu->kvm, gpa, data, len);
}
/**
* read_guest_lc - copy data from guest vcpu's lowcore to kernel space
* @vcpu: virtual cpu
* @gra: vcpu's source guest real address
* @data: destination address in kernel space
* @len: number of bytes to copy
*
* Copy data from guest vcpu's lowcore to kernel space. The entire range must
* be located within the vcpu's lowcore, otherwise the result is undefined.
*
* Returns zero on success or -EFAULT on error.
*
* Note: an error indicates that either the kernel is out of memory or
* the guest memory mapping is broken. In any case the best solution
* would be to terminate the guest.
* It is wrong to inject a guest exception.
*/
static inline __must_check
int read_guest_lc(struct kvm_vcpu *vcpu, unsigned long gra, void *data,
unsigned long len)
{
unsigned long gpa = gra + kvm_s390_get_prefix(vcpu);
return kvm_read_guest(vcpu->kvm, gpa, data, len);
}
enum gacc_mode {
GACC_FETCH,
GACC_STORE,
GACC_IFETCH,
};
int guest_translate_address_with_key(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar,
unsigned long *gpa, enum gacc_mode mode,
u8 access_key);
int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar,
unsigned long length, enum gacc_mode mode, u8 access_key);
int check_gpa_range(struct kvm *kvm, unsigned long gpa, unsigned long length,
enum gacc_mode mode, u8 access_key);
int access_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, void *data,
unsigned long len, enum gacc_mode mode, u8 access_key);
int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
void *data, unsigned long len, enum gacc_mode mode,
u8 access_key);
int access_guest_real(struct kvm_vcpu *vcpu, unsigned long gra,
void *data, unsigned long len, enum gacc_mode mode);
int cmpxchg_guest_abs_with_key(struct kvm *kvm, gpa_t gpa, int len, __uint128_t *old,
__uint128_t new, u8 access_key, bool *success);
/**
* write_guest_with_key - copy data from kernel space to guest space
* @vcpu: virtual cpu
* @ga: guest address
* @ar: access register
* @data: source address in kernel space
* @len: number of bytes to copy
* @access_key: access key the storage key needs to match
*
* Copy @len bytes from @data (kernel space) to @ga (guest address).
* In order to copy data to guest space the PSW of the vcpu is inspected:
* If DAT is off data will be copied to guest real or absolute memory.
* If DAT is on data will be copied to the address space as specified by
* the address space bits of the PSW:
* Primary, secondary, home space or access register mode.
* The addressing mode of the PSW is also inspected, so that address wrap
* around is taken into account for 24-, 31- and 64-bit addressing mode,
* if the to be copied data crosses page boundaries in guest address space.
* In addition low address, DAT and key protection checks are performed before
* copying any data.
*
* This function modifies the 'struct kvm_s390_pgm_info pgm' member of @vcpu.
* In case of an access exception (e.g. protection exception) pgm will contain
* all data necessary so that a subsequent call to 'kvm_s390_inject_prog_vcpu()'
* will inject a correct exception into the guest.
* If no access exception happened, the contents of pgm are undefined when
* this function returns.
*
* Returns: - zero on success
* - a negative value if e.g. the guest mapping is broken or in
* case of out-of-memory. In this case the contents of pgm are
* undefined. Also parts of @data may have been copied to guest
* space.
* - a positive value if an access exception happened. In this case
* the returned value is the program interruption code and the
* contents of pgm may be used to inject an exception into the
* guest. No data has been copied to guest space.
*
* Note: in case an access exception is recognized no data has been copied to
* guest space (this is also true, if the to be copied data would cross
* one or more page boundaries in guest space).
* Therefore this function may be used for nullifying and suppressing
* instruction emulation.
* It may also be used for terminating instructions, if it is undefined
* if data has been changed in guest space in case of an exception.
*/
static inline __must_check
int write_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
void *data, unsigned long len, u8 access_key)
{
return access_guest_with_key(vcpu, ga, ar, data, len, GACC_STORE,
access_key);
}
/**
* write_guest - copy data from kernel space to guest space
* @vcpu: virtual cpu
* @ga: guest address
* @ar: access register
* @data: source address in kernel space
* @len: number of bytes to copy
*
* The behaviour of write_guest is identical to write_guest_with_key, except
* that the PSW access key is used instead of an explicit argument.
*/
static inline __must_check
int write_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data,
unsigned long len)
{
u8 access_key = psw_bits(vcpu->arch.sie_block->gpsw).key;
return write_guest_with_key(vcpu, ga, ar, data, len, access_key);
}
/**
* read_guest_with_key - copy data from guest space to kernel space
* @vcpu: virtual cpu
* @ga: guest address
* @ar: access register
* @data: destination address in kernel space
* @len: number of bytes to copy
* @access_key: access key the storage key needs to match
*
* Copy @len bytes from @ga (guest address) to @data (kernel space).
*
* The behaviour of read_guest_with_key is identical to write_guest_with_key,
* except that data will be copied from guest space to kernel space.
*/
static inline __must_check
int read_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
void *data, unsigned long len, u8 access_key)
{
return access_guest_with_key(vcpu, ga, ar, data, len, GACC_FETCH,
access_key);
}
/**
* read_guest - copy data from guest space to kernel space
* @vcpu: virtual cpu
* @ga: guest address
* @ar: access register
* @data: destination address in kernel space
* @len: number of bytes to copy
*
* Copy @len bytes from @ga (guest address) to @data (kernel space).
*
* The behaviour of read_guest is identical to read_guest_with_key, except
* that the PSW access key is used instead of an explicit argument.
*/
static inline __must_check
int read_guest(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar, void *data,
unsigned long len)
{
u8 access_key = psw_bits(vcpu->arch.sie_block->gpsw).key;
return read_guest_with_key(vcpu, ga, ar, data, len, access_key);
}
/**
* read_guest_instr - copy instruction data from guest space to kernel space
* @vcpu: virtual cpu
* @ga: guest address
* @data: destination address in kernel space
* @len: number of bytes to copy
*
* Copy @len bytes from the given address (guest space) to @data (kernel
* space).
*
* The behaviour of read_guest_instr is identical to read_guest, except that
* instruction data will be read from primary space when in home-space or
* address-space mode.
*/
static inline __must_check
int read_guest_instr(struct kvm_vcpu *vcpu, unsigned long ga, void *data,
unsigned long len)
{
u8 access_key = psw_bits(vcpu->arch.sie_block->gpsw).key;
return access_guest_with_key(vcpu, ga, 0, data, len, GACC_IFETCH,
access_key);
}
/**
* write_guest_abs - copy data from kernel space to guest space absolute
* @vcpu: virtual cpu
* @gpa: guest physical (absolute) address
* @data: source address in kernel space
* @len: number of bytes to copy
*
* Copy @len bytes from @data (kernel space) to @gpa (guest absolute address).
* It is up to the caller to ensure that the entire guest memory range is
* valid memory before calling this function.
* Guest low address and key protection are not checked.
*
* Returns zero on success or -EFAULT on error.
*
* If an error occurs data may have been copied partially to guest memory.
*/
static inline __must_check
int write_guest_abs(struct kvm_vcpu *vcpu, unsigned long gpa, void *data,
unsigned long len)
{
return kvm_write_guest(vcpu->kvm, gpa, data, len);
}
/**
* read_guest_abs - copy data from guest space absolute to kernel space
* @vcpu: virtual cpu
* @gpa: guest physical (absolute) address
* @data: destination address in kernel space
* @len: number of bytes to copy
*
* Copy @len bytes from @gpa (guest absolute address) to @data (kernel space).
* It is up to the caller to ensure that the entire guest memory range is
* valid memory before calling this function.
* Guest key protection is not checked.
*
* Returns zero on success or -EFAULT on error.
*
* If an error occurs data may have been copied partially to kernel space.
*/
static inline __must_check
int read_guest_abs(struct kvm_vcpu *vcpu, unsigned long gpa, void *data,
unsigned long len)
{
return kvm_read_guest(vcpu->kvm, gpa, data, len);
}
/**
* write_guest_real - copy data from kernel space to guest space real
* @vcpu: virtual cpu
* @gra: guest real address
* @data: source address in kernel space
* @len: number of bytes to copy
*
* Copy @len bytes from @data (kernel space) to @gra (guest real address).
* Guest low address and key protection are not checked.
*
* Returns zero on success, -EFAULT when copying from @data failed, or
* PGM_ADRESSING in case @gra is outside a memslot. In this case, pgm check info
* is also stored to allow injecting into the guest (if applicable) using
* kvm_s390_inject_prog_cond().
*
* If an error occurs data may have been copied partially to guest memory.
*/
static inline __must_check
int write_guest_real(struct kvm_vcpu *vcpu, unsigned long gra, void *data,
unsigned long len)
{
return access_guest_real(vcpu, gra, data, len, 1);
}
/**
* read_guest_real - copy data from guest space real to kernel space
* @vcpu: virtual cpu
* @gra: guest real address
* @data: destination address in kernel space
* @len: number of bytes to copy
*
* Copy @len bytes from @gra (guest real address) to @data (kernel space).
* Guest key protection is not checked.
*
* Returns zero on success, -EFAULT when copying to @data failed, or
* PGM_ADRESSING in case @gra is outside a memslot. In this case, pgm check info
* is also stored to allow injecting into the guest (if applicable) using
* kvm_s390_inject_prog_cond().
*
* If an error occurs data may have been copied partially to kernel space.
*/
static inline __must_check
int read_guest_real(struct kvm_vcpu *vcpu, unsigned long gra, void *data,
unsigned long len)
{
return access_guest_real(vcpu, gra, data, len, 0);
}
void ipte_lock(struct kvm *kvm);
void ipte_unlock(struct kvm *kvm);
int ipte_lock_held(struct kvm *kvm);
int kvm_s390_check_low_addr_prot_real(struct kvm_vcpu *vcpu, unsigned long gra);
/* MVPG PEI indication bits */
#define PEI_DAT_PROT 2
#define PEI_NOT_PTE 4
int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *shadow,
unsigned long saddr, unsigned long *datptr);
#endif /* __KVM_S390_GACCESS_H */
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