s390/uaccess: add cmpxchg_user_key()
Add cmpxchg_user_key() which allows to execute a compare and exchange on a user space address. This allows also to specify a storage key which makes sure that key-controlled protection is considered. This is based on a patch written by Janis Schoetterl-Glausch. Link: https://lore.kernel.org/all/20220930210751.225873-2-scgl@linux.ibm.com Cc: Janis Schoetterl-Glausch <scgl@linux.ibm.com> Link: https://lore.kernel.org/r/Y2J8axs+bcQ2dO/l@osiris Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens
parent
f39a8c4a22
commit
4148575abe
@ -390,4 +390,187 @@ do { \
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goto err_label; \
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} while (0)
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void __cmpxchg_user_key_called_with_bad_pointer(void);
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static __always_inline int __cmpxchg_user_key(unsigned long address, void *uval,
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__uint128_t old, __uint128_t new,
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unsigned long key, int size)
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{
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int rc = 0;
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switch (size) {
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case 1: {
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unsigned int prev, tmp, shift;
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shift = (3 ^ (address & 3)) << 3;
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address ^= address & 3;
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asm volatile(
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" spka 0(%[key])\n"
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" sacf 256\n"
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"0: l %[prev],%[address]\n"
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"1: nr %[prev],%[mask]\n"
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" lr %[tmp],%[prev]\n"
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" or %[prev],%[old]\n"
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" or %[tmp],%[new]\n"
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"2: cs %[prev],%[tmp],%[address]\n"
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"3: jnl 4f\n"
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" xr %[tmp],%[prev]\n"
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" nr %[tmp],%[mask]\n"
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" jnz 1b\n"
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"4: sacf 768\n"
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" spka %[default_key]\n"
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EX_TABLE_UA_LOAD_REG(0b, 4b, %[rc], %[prev])
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EX_TABLE_UA_LOAD_REG(1b, 4b, %[rc], %[prev])
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EX_TABLE_UA_LOAD_REG(2b, 4b, %[rc], %[prev])
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EX_TABLE_UA_LOAD_REG(3b, 4b, %[rc], %[prev])
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: [rc] "+&d" (rc),
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[prev] "=&d" (prev),
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[tmp] "=&d" (tmp),
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[address] "+Q" (*(int *)address)
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: [old] "d" (((unsigned int)old & 0xff) << shift),
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[new] "d" (((unsigned int)new & 0xff) << shift),
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[mask] "d" (~(0xff << shift)),
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[key] "a" (key << 4),
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[default_key] "J" (PAGE_DEFAULT_KEY)
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: "memory", "cc");
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*(unsigned char *)uval = prev >> shift;
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return rc;
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}
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case 2: {
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unsigned int prev, tmp, shift;
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shift = (2 ^ (address & 2)) << 3;
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address ^= address & 2;
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asm volatile(
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" spka 0(%[key])\n"
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" sacf 256\n"
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"0: l %[prev],%[address]\n"
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"1: nr %[prev],%[mask]\n"
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" lr %[tmp],%[prev]\n"
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" or %[prev],%[old]\n"
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" or %[tmp],%[new]\n"
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"2: cs %[prev],%[tmp],%[address]\n"
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"3: jnl 4f\n"
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" xr %[tmp],%[prev]\n"
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" nr %[tmp],%[mask]\n"
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" jnz 1b\n"
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"4: sacf 768\n"
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" spka %[default_key]\n"
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EX_TABLE_UA_LOAD_REG(0b, 4b, %[rc], %[prev])
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EX_TABLE_UA_LOAD_REG(1b, 4b, %[rc], %[prev])
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EX_TABLE_UA_LOAD_REG(2b, 4b, %[rc], %[prev])
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EX_TABLE_UA_LOAD_REG(3b, 4b, %[rc], %[prev])
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: [rc] "+&d" (rc),
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[prev] "=&d" (prev),
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[tmp] "=&d" (tmp),
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[address] "+Q" (*(int *)address)
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: [old] "d" (((unsigned int)old & 0xffff) << shift),
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[new] "d" (((unsigned int)new & 0xffff) << shift),
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[mask] "d" (~(0xffff << shift)),
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[key] "a" (key << 4),
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[default_key] "J" (PAGE_DEFAULT_KEY)
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: "memory", "cc");
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*(unsigned short *)uval = prev >> shift;
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return rc;
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}
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case 4: {
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unsigned int prev = old;
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asm volatile(
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" spka 0(%[key])\n"
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" sacf 256\n"
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"0: cs %[prev],%[new],%[address]\n"
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"1: sacf 768\n"
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" spka %[default_key]\n"
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EX_TABLE_UA_LOAD_REG(0b, 1b, %[rc], %[prev])
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EX_TABLE_UA_LOAD_REG(1b, 1b, %[rc], %[prev])
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: [rc] "+&d" (rc),
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[prev] "+&d" (prev),
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[address] "+Q" (*(int *)address)
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: [new] "d" ((unsigned int)new),
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[key] "a" (key << 4),
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[default_key] "J" (PAGE_DEFAULT_KEY)
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: "memory", "cc");
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*(unsigned int *)uval = prev;
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return rc;
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}
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case 8: {
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unsigned long prev = old;
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asm volatile(
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" spka 0(%[key])\n"
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" sacf 256\n"
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"0: csg %[prev],%[new],%[address]\n"
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"1: sacf 768\n"
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" spka %[default_key]\n"
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EX_TABLE_UA_LOAD_REG(0b, 1b, %[rc], %[prev])
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EX_TABLE_UA_LOAD_REG(1b, 1b, %[rc], %[prev])
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: [rc] "+&d" (rc),
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[prev] "+&d" (prev),
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[address] "+QS" (*(long *)address)
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: [new] "d" ((unsigned long)new),
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[key] "a" (key << 4),
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[default_key] "J" (PAGE_DEFAULT_KEY)
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: "memory", "cc");
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*(unsigned long *)uval = prev;
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return rc;
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}
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case 16: {
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__uint128_t prev = old;
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asm volatile(
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" spka 0(%[key])\n"
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" sacf 256\n"
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"0: cdsg %[prev],%[new],%[address]\n"
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"1: sacf 768\n"
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" spka %[default_key]\n"
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EX_TABLE_UA_LOAD_REGPAIR(0b, 1b, %[rc], %[prev])
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EX_TABLE_UA_LOAD_REGPAIR(1b, 1b, %[rc], %[prev])
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: [rc] "+&d" (rc),
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[prev] "+&d" (prev),
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[address] "+QS" (*(__int128_t *)address)
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: [new] "d" (new),
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[key] "a" (key << 4),
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[default_key] "J" (PAGE_DEFAULT_KEY)
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: "memory", "cc");
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*(__uint128_t *)uval = prev;
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return rc;
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}
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}
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__cmpxchg_user_key_called_with_bad_pointer();
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return rc;
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}
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/**
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* cmpxchg_user_key() - cmpxchg with user space target, honoring storage keys
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* @ptr: User space address of value to compare to @old and exchange with
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* @new. Must be aligned to sizeof(*@ptr).
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* @uval: Address where the old value of *@ptr is written to.
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* @old: Old value. Compared to the content pointed to by @ptr in order to
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* determine if the exchange occurs. The old value read from *@ptr is
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* written to *@uval.
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* @new: New value to place at *@ptr.
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* @key: Access key to use for checking storage key protection.
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*
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* Perform a cmpxchg on a user space target, honoring storage key protection.
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* @key alone determines how key checking is performed, neither
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* storage-protection-override nor fetch-protection-override apply.
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* The caller must compare *@uval and @old to determine if values have been
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* exchanged. In case of an exception *@uval is set to zero.
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*
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* Return: 0: cmpxchg executed
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* -EFAULT: an exception happened when trying to access *@ptr
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*/
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#define cmpxchg_user_key(ptr, uval, old, new, key) \
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({ \
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__typeof__(ptr) __ptr = (ptr); \
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__typeof__(uval) __uval = (uval); \
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\
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BUILD_BUG_ON(sizeof(*(__ptr)) != sizeof(*(__uval))); \
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might_fault(); \
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__chk_user_ptr(__ptr); \
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__cmpxchg_user_key((unsigned long)(__ptr), (void *)(__uval), \
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(old), (new), (key), sizeof(*(__ptr))); \
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})
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#endif /* __S390_UACCESS_H */
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