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x86/usercopy: Remove .fixup usage

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Typically usercopy does whole word copies followed by a number of byte
copies to finish the tail. This means that on exception it needs to
compute the remaining length as: words*sizeof(long) + bytes.

Create a new extable handler to do just this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20211110101326.081701085@infradead.org
This commit is contained in:
Peter Zijlstra 2021-11-10 11:01:22 +01:00
parent 13e4bf1bdd
commit d5d797dcbd
4 changed files with 22 additions and 28 deletions
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5
arch/x86/include/asm/extable_fixup_types.h
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@ -50,4 +50,9 @@
#define EX_TYPE_FAULT_SGX 18
#define EX_TYPE_UCOPY_LEN 19 /* cx := reg + imm*cx */
#define EX_TYPE_UCOPY_LEN1 (EX_TYPE_UCOPY_LEN | EX_DATA_IMM(1))
#define EX_TYPE_UCOPY_LEN4 (EX_TYPE_UCOPY_LEN | EX_DATA_IMM(4))
#define EX_TYPE_UCOPY_LEN8 (EX_TYPE_UCOPY_LEN | EX_DATA_IMM(8))
#endif

28
arch/x86/lib/usercopy_32.c
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@ -42,11 +42,7 @@ do { \
" movl %2,%0\n" \
"1: rep; stosb\n" \
"2: " ASM_CLAC "\n" \
".section .fixup,\"ax\"\n" \
"3: lea 0(%2,%0,4),%0\n" \
" jmp 2b\n" \
".previous\n" \
_ASM_EXTABLE_UA(0b, 3b) \
_ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UCOPY_LEN4, %2) \
_ASM_EXTABLE_UA(1b, 2b) \
: "=&c"(size), "=&D" (__d0) \
: "r"(size & 3), "0"(size / 4), "1"(addr), "a"(0)); \
@ -148,10 +144,6 @@ __copy_user_intel(void __user *to, const void *from, unsigned long size)
"36: movl %%eax, %0\n"
"37: rep; movsb\n"
"100:\n"
".section .fixup,\"ax\"\n"
"101: lea 0(%%eax,%0,4),%0\n"
" jmp 100b\n"
".previous\n"
_ASM_EXTABLE_UA(1b, 100b)
_ASM_EXTABLE_UA(2b, 100b)
_ASM_EXTABLE_UA(3b, 100b)
@ -189,7 +181,7 @@ __copy_user_intel(void __user *to, const void *from, unsigned long size)
_ASM_EXTABLE_UA(35b, 100b)
_ASM_EXTABLE_UA(36b, 100b)
_ASM_EXTABLE_UA(37b, 100b)
_ASM_EXTABLE_UA(99b, 101b)
_ASM_EXTABLE_TYPE_REG(99b, 100b, EX_TYPE_UCOPY_LEN4, %%eax)
: "=&c"(size), "=&D" (d0), "=&S" (d1)
: "1"(to), "2"(from), "0"(size)
: "eax", "edx", "memory");
@ -254,10 +246,6 @@ static unsigned long __copy_user_intel_nocache(void *to,
" movl %%eax,%0\n"
"7: rep; movsb\n"
"8:\n"
".section .fixup,\"ax\"\n"
"9: lea 0(%%eax,%0,4),%0\n"
" jmp 8b\n"
".previous\n"
_ASM_EXTABLE_UA(0b, 8b)
_ASM_EXTABLE_UA(1b, 8b)
_ASM_EXTABLE_UA(2b, 8b)
@ -276,7 +264,7 @@ static unsigned long __copy_user_intel_nocache(void *to,
_ASM_EXTABLE_UA(81b, 8b)
_ASM_EXTABLE_UA(14b, 8b)
_ASM_EXTABLE_UA(91b, 8b)
_ASM_EXTABLE_UA(6b, 9b)
_ASM_EXTABLE_TYPE_REG(6b, 8b, EX_TYPE_UCOPY_LEN4, %%eax)
_ASM_EXTABLE_UA(7b, 8b)
: "=&c"(size), "=&D" (d0), "=&S" (d1)
: "1"(to), "2"(from), "0"(size)
@ -314,14 +302,8 @@ do { \
" movl %3,%0\n" \
"1: rep; movsb\n" \
"2:\n" \
".section .fixup,\"ax\"\n" \
"5: addl %3,%0\n" \
" jmp 2b\n" \
"3: lea 0(%3,%0,4),%0\n" \
" jmp 2b\n" \
".previous\n" \
_ASM_EXTABLE_UA(4b, 5b) \
_ASM_EXTABLE_UA(0b, 3b) \
_ASM_EXTABLE_TYPE_REG(4b, 2b, EX_TYPE_UCOPY_LEN1, %3) \
_ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UCOPY_LEN4, %3) \
_ASM_EXTABLE_UA(1b, 2b) \
: "=&c"(size), "=&D" (__d0), "=&S" (__d1), "=r"(__d2) \
: "3"(size), "0"(size), "1"(to), "2"(from) \

8
arch/x86/lib/usercopy_64.c
View File

@ -35,12 +35,10 @@ unsigned long __clear_user(void __user *addr, unsigned long size)
" incq %[dst]\n"
" decl %%ecx ; jnz 1b\n"
"2:\n"
".section .fixup,\"ax\"\n"
"3: lea 0(%[size1],%[size8],8),%[size8]\n"
" jmp 2b\n"
".previous\n"
_ASM_EXTABLE_UA(0b, 3b)
_ASM_EXTABLE_TYPE_REG(0b, 2b, EX_TYPE_UCOPY_LEN8, %[size1])
_ASM_EXTABLE_UA(1b, 2b)
: [size8] "=&c"(size), [dst] "=&D" (__d0)
: [size1] "r"(size & 7), "[size8]" (size / 8), "[dst]"(addr));
clac();

9
arch/x86/mm/extable.c
View File

@ -145,6 +145,13 @@ static bool ex_handler_imm_reg(const struct exception_table_entry *fixup,
return ex_handler_default(fixup, regs);
}
static bool ex_handler_ucopy_len(const struct exception_table_entry *fixup,
struct pt_regs *regs, int trapnr, int reg, int imm)
{
regs->cx = imm * regs->cx + *pt_regs_nr(regs, reg);
return ex_handler_uaccess(fixup, regs, trapnr);
}
int ex_get_fixup_type(unsigned long ip)
{
const struct exception_table_entry *e = search_exception_tables(ip);
@ -217,6 +224,8 @@ int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,
return ex_handler_imm_reg(e, regs, reg, imm);
case EX_TYPE_FAULT_SGX:
return ex_handler_sgx(e, regs, trapnr);
case EX_TYPE_UCOPY_LEN:
return ex_handler_ucopy_len(e, regs, trapnr, reg, imm);
}
BUG();
}