[PATCH 19/22] x86,usercopy: Remove .fixup usage

Peter Zijlstra
2021-11-05T17:20:21Z

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>
---
arch/x86/include/asm/extable_fixup_types.h | 5 +++++
arch/x86/lib/usercopy_32.c | 28 +++++-----------------------
arch/x86/lib/usercopy_64.c | 8 +++-----
arch/x86/mm/extable.c | 9 +++++++++
4 files changed, 22 insertions(+), 28 deletions(-)

--- a/arch/x86/include/asm/extable_fixup_types.h
+++ b/arch/x86/include/asm/extable_fixup_types.h
@@ -46,4 +46,9 @@

#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
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -43,11 +43,7 @@ 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)); \
@@ -149,10 +145,6 @@ __copy_user_intel(void __user *to, const
"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)
@@ -190,7 +182,7 @@ __copy_user_intel(void __user *to, const
_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");
@@ -255,10 +247,6 @@ static unsigned long __copy_user_intel_n
" 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)
@@ -277,7 +265,7 @@ static unsigned long __copy_user_intel_n
_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)
@@ -315,14 +303,8 @@ 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) \
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -35,12 +35,10 @@ unsigned long __clear_user(void __user *
" 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();
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -145,6 +145,13 @@ static bool ex_handler_imm_reg(const str
return ex_handler_default(fixup, regs);
}

+static bool ex_handler_ucopy_leng(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
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_leng(e, regs, trapnr, reg, imm);
}
BUG();
}