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authorChristophe Leroy2021-11-29 18:49:41 +0100
committerMichael Ellerman2021-12-09 22:41:21 +1100
commit0d76914a4c99ab5658f3fb07cdf3799d28e2eab3 (patch)
treea3223a5b9b13f5cb2f5499d44c99a6c7aeeb905e
parent9b307576f37136d37d5e42b1d8713ec34a601a62 (diff)
powerpc/inst: Optimise copy_inst_from_kernel_nofault()
copy_inst_from_kernel_nofault() uses copy_from_kernel_nofault() to copy one or two 32bits words. This means calling an out-of-line function which itself calls back copy_from_kernel_nofault_allowed() then performs a generic copy with loops. Rewrite copy_inst_from_kernel_nofault() to do everything at a single place and use __get_kernel_nofault() directly to perform single accesses without loops. Allthough the generic function uses pagefault_disable(), it is not required on powerpc because do_page_fault() bails earlier when a kernel mode fault happens on a kernel address. As the function has now become very small, inline it. With this change, on an 8xx the time spent in the loop in ftrace_replace_code() is reduced by 23% at function tracer activation and 27% at nop tracer activation. The overall time to activate function tracer (measured with shell command 'time') is 570ms before the patch and 470ms after the patch. Even vmlinux size is reduced (by 152 instruction). Before the patch: 00000018 <copy_inst_from_kernel_nofault>: 18: 94 21 ff e0 stwu r1,-32(r1) 1c: 7c 08 02 a6 mflr r0 20: 38 a0 00 04 li r5,4 24: 93 e1 00 1c stw r31,28(r1) 28: 7c 7f 1b 78 mr r31,r3 2c: 38 61 00 08 addi r3,r1,8 30: 90 01 00 24 stw r0,36(r1) 34: 48 00 00 01 bl 34 <copy_inst_from_kernel_nofault+0x1c> 34: R_PPC_REL24 copy_from_kernel_nofault 38: 2c 03 00 00 cmpwi r3,0 3c: 40 82 00 0c bne 48 <copy_inst_from_kernel_nofault+0x30> 40: 81 21 00 08 lwz r9,8(r1) 44: 91 3f 00 00 stw r9,0(r31) 48: 80 01 00 24 lwz r0,36(r1) 4c: 83 e1 00 1c lwz r31,28(r1) 50: 38 21 00 20 addi r1,r1,32 54: 7c 08 03 a6 mtlr r0 58: 4e 80 00 20 blr After the patch (before inlining): 00000018 <copy_inst_from_kernel_nofault>: 18: 3d 20 b0 00 lis r9,-20480 1c: 7c 04 48 40 cmplw r4,r9 20: 7c 69 1b 78 mr r9,r3 24: 41 80 00 14 blt 38 <copy_inst_from_kernel_nofault+0x20> 28: 81 44 00 00 lwz r10,0(r4) 2c: 38 60 00 00 li r3,0 30: 91 49 00 00 stw r10,0(r9) 34: 4e 80 00 20 blr 38: 38 60 ff de li r3,-34 3c: 4e 80 00 20 blr 40: 38 60 ff f2 li r3,-14 44: 4e 80 00 20 blr Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> [mpe: Add clang workaround, with version check as suggested by Nathan] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/0d5b12183d5176dd702d29ad94c39c384e51c78f.1638208156.git.christophe.leroy@csgroup.eu
-rw-r--r--arch/powerpc/include/asm/inst.h25
-rw-r--r--arch/powerpc/mm/maccess.c17
2 files changed, 24 insertions, 18 deletions
diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
index 53a40faf362a..95e5243d2997 100644
--- a/arch/powerpc/include/asm/inst.h
+++ b/arch/powerpc/include/asm/inst.h
@@ -4,6 +4,8 @@
#include <asm/ppc-opcode.h>
#include <asm/reg.h>
+#include <asm/disassemble.h>
+#include <asm/uaccess.h>
#define ___get_user_instr(gu_op, dest, ptr) \
({ \
@@ -148,6 +150,27 @@ static inline char *__ppc_inst_as_str(char str[PPC_INST_STR_LEN], ppc_inst_t x)
__str; \
})
-int copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src);
+static inline int copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
+{
+ unsigned int val, suffix;
+
+ if (unlikely(!is_kernel_addr((unsigned long)src)))
+ return -ERANGE;
+
+/* See https://github.com/ClangBuiltLinux/linux/issues/1521 */
+#if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 140000
+ val = suffix = 0;
+#endif
+ __get_kernel_nofault(&val, src, u32, Efault);
+ if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
+ __get_kernel_nofault(&suffix, src + 1, u32, Efault);
+ *inst = ppc_inst_prefix(val, suffix);
+ } else {
+ *inst = ppc_inst(val);
+ }
+ return 0;
+Efault:
+ return -EFAULT;
+}
#endif /* _ASM_POWERPC_INST_H */
diff --git a/arch/powerpc/mm/maccess.c b/arch/powerpc/mm/maccess.c
index 5abae96b2b46..ea821d0ffe16 100644
--- a/arch/powerpc/mm/maccess.c
+++ b/arch/powerpc/mm/maccess.c
@@ -11,20 +11,3 @@ bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
{
return is_kernel_addr((unsigned long)unsafe_src);
}
-
-int copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
-{
- unsigned int val, suffix;
- int err;
-
- err = copy_from_kernel_nofault(&val, src, sizeof(val));
- if (err)
- return err;
- if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
- err = copy_from_kernel_nofault(&suffix, src + 1, sizeof(suffix));
- *inst = ppc_inst_prefix(val, suffix);
- } else {
- *inst = ppc_inst(val);
- }
- return err;
-}