[tip: x86/core] x86/usercopy: Remove .fixup usage

From: tip-bot2 for Peter Zijlstra
Date: Mon Dec 13 2021 - 04:55:03 EST

The following commit has been merged into the x86/core branch of tip:

Commit-ID: d5d797dcbd781cb7c526ad32f31c7fd96babfdb2
Gitweb: https://git.kernel.org/tip/d5d797dcbd781cb7c526ad32f31c7fd96babfdb2
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Wed, 10 Nov 2021 11:01:22 +01:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Sat, 11 Dec 2021 09:09:50 +01:00

x86/usercopy: Remove .fixup usage

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@xxxxxxxxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211110101326.081701085@xxxxxxxxxxxxx
---
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(-)

diff --git a/arch/x86/include/asm/extable_fixup_types.h b/arch/x86/include/asm/extable_fixup_types.h
index 8278ed2..b5ab333 100644
--- a/arch/x86/include/asm/extable_fixup_types.h
+++ b/arch/x86/include/asm/extable_fixup_types.h
@@ -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
diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c
index 1eb1506..422257c 100644
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -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) \
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index 508c81e..0402a74 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -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();
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index c869f43..41eaa64 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -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();
}