[PATCH v2 10/14] powerpc: Provide syscall wrapper
Rohan McLure
rmclure at linux.ibm.com
Mon Jul 25 16:30:24 AEST 2022
Implement syscall wrapper as per s390, x86, arm64. When enabled
cause handlers to accept parameters from a stack frame rather than
from user scratch register state. This allows for user registers to be
safely cleared in order to reduce caller influence on speculation
within syscall routine. The wrapper is a macro that emits syscall
handler symbols that call into the target handler, obtaining its
parameters from a struct pt_regs on the stack.
As registers are already saved to the stack prior to calling
system_call_exception, it appears that this function is executed more
efficiently with the new stack-pointer convention than with parameters
passed by registers, avoiding the allocation of a stack frame for this
method. On a 32-bit system, we see >20% performance increases on the
null_syscall microbenchmark, and on a Power 8 the performance gains
amortise the cost of clearing and restoring registers which is
implemented at the end of this series, seeing final result of ~5.6%
performance improvement on null_syscall.
Syscalls are wrapped in this fashion on all platforms except for the
Cell processor as this commit does not provide SPU support. This can be
quickly fixed in a successive patch, but requires spu_sys_callback to
allocate a pt_regs structure to satisfy the wrapped calling convention.
Co-developed-by: Andrew Donnellan <ajd at linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd at linux.ibm.com>
Signed-off-by: Rohan McLure <rmclure at linux.ibm.com>
---
V1 -> V2: Generate prototypes for symbols produced by the wrapper.
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/interrupt.h | 3 +-
arch/powerpc/include/asm/syscall.h | 4 +
arch/powerpc/include/asm/syscall_wrapper.h | 94 ++++++++++++++++++++
arch/powerpc/include/asm/syscalls.h | 25 +++++-
arch/powerpc/kernel/entry_32.S | 6 +-
arch/powerpc/kernel/interrupt.c | 31 +++----
arch/powerpc/kernel/interrupt_64.S | 30 +++----
arch/powerpc/kernel/systbl.c | 2 +
arch/powerpc/kernel/vdso.c | 2 +
10 files changed, 156 insertions(+), 42 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 26331cdd3642..447bd34b5b87 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -137,6 +137,7 @@ config PPC
select ARCH_HAS_STRICT_KERNEL_RWX if (PPC_BOOK3S || PPC_8xx || 40x) && !HIBERNATION
select ARCH_HAS_STRICT_KERNEL_RWX if FSL_BOOKE && !HIBERNATION && !RANDOMIZE_BASE
select ARCH_HAS_STRICT_MODULE_RWX if ARCH_HAS_STRICT_KERNEL_RWX
+ select ARCH_HAS_SYSCALL_WRAPPER if !SPU_BASE
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAS_UACCESS_FLUSHCACHE
select ARCH_HAS_UBSAN_SANITIZE_ALL
diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 8069dbc4b8d1..3f9cad81585c 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -665,8 +665,7 @@ static inline void interrupt_cond_local_irq_enable(struct pt_regs *regs)
local_irq_enable();
}
-long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
- unsigned long r0, struct pt_regs *regs);
+long system_call_exception(unsigned long r0, struct pt_regs *regs);
notrace unsigned long syscall_exit_prepare(unsigned long r3, struct pt_regs *regs, long scv);
notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs);
notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs);
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index d2a8dfd5de33..3dd36c5e334a 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -14,8 +14,12 @@
#include <linux/sched.h>
#include <linux/thread_info.h>
+#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+typedef long (*syscall_fn)(const struct pt_regs *);
+#else
typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
unsigned long, unsigned long, unsigned long);
+#endif
/* ftrace syscalls requires exporting the sys_call_table */
extern const syscall_fn sys_call_table[];
diff --git a/arch/powerpc/include/asm/syscall_wrapper.h b/arch/powerpc/include/asm/syscall_wrapper.h
new file mode 100644
index 000000000000..ebeffcb08d3d
--- /dev/null
+++ b/arch/powerpc/include/asm/syscall_wrapper.h
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * syscall_wrapper.h - powerpc specific wrappers to syscall definitions
+ *
+ * Based on arch/{x86,arm64}/include/asm/syscall_wrapper.h
+ */
+
+#ifndef __ASM_SYSCALL_WRAPPER_H
+#define __ASM_SYSCALL_WRAPPER_H
+
+struct pt_regs;
+
+#define SC_POWERPC_REGS_TO_ARGS(x, ...) \
+ __MAP(x,__SC_ARGS \
+ ,,regs->gpr[3],,regs->gpr[4],,regs->gpr[5] \
+ ,,regs->gpr[6],,regs->gpr[7],,regs->gpr[8])
+
+#ifdef CONFIG_COMPAT
+
+#define COMPAT_SYSCALL_DEFINEx(x, name, ...) \
+ asmlinkage long __powerpc_compat_sys##name(const struct pt_regs *regs); \
+ ALLOW_ERROR_INJECTION(__powerpc_compat_sys##name, ERRNO); \
+ static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
+ static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
+ asmlinkage long __powerpc_compat_sys##name(const struct pt_regs *regs) \
+ { \
+ return __se_compat_sys##name(SC_POWERPC_REGS_TO_ARGS(x,__VA_ARGS__)); \
+ } \
+ static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
+ { \
+ return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__)); \
+ } \
+ static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+#define COMPAT_SYSCALL_DEFINE0(sname) \
+ asmlinkage long __powerpc_compat_sys_##sname(const struct pt_regs *__unused); \
+ ALLOW_ERROR_INJECTION(__powerpc_compat_sys_##sname, ERRNO); \
+ asmlinkage long __powerpc_compat_sys_##sname(const struct pt_regs *__unused)
+
+#define COND_SYSCALL_COMPAT(name) \
+ long __powerpc_compat_sys_##name(const struct pt_regs *regs); \
+ asmlinkage long __weak __powerpc_compat_sys_##name(const struct pt_regs *regs) \
+ { \
+ return sys_ni_syscall(); \
+ }
+#define COMPAT_SYS_NI(name) \
+ SYSCALL_ALIAS(__powerpc_compat_sys_##name, sys_ni_posix_timers);
+
+#endif /* CONFIG_COMPAT */
+
+#define __SYSCALL_DEFINEx(x, name, ...) \
+ asmlinkage long __powerpc_sys##name(const struct pt_regs *regs); \
+ ALLOW_ERROR_INJECTION(__powerpc_sys##name, ERRNO); \
+ long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
+ static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)); \
+ static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)); \
+ asmlinkage long __powerpc_sys##name(const struct pt_regs *regs) \
+ { \
+ return __se_sys##name(SC_POWERPC_REGS_TO_ARGS(x,__VA_ARGS__)); \
+ } \
+ long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__)) \
+ { \
+ return __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
+ } \
+ static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__)) \
+ { \
+ long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__)); \
+ __MAP(x,__SC_TEST,__VA_ARGS__); \
+ __PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__)); \
+ return ret; \
+ } \
+ static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+#define SYSCALL_DEFINE0(sname) \
+ SYSCALL_METADATA(_##sname, 0); \
+ long sys_##sname(void); \
+ asmlinkage long __powerpc_sys_##sname(const struct pt_regs *__unused); \
+ ALLOW_ERROR_INJECTION(__powerpc_sys_##sname, ERRNO); \
+ long sys_##sname(void) \
+ { \
+ return __powerpc_sys_##sname(NULL); \
+ } \
+ asmlinkage long __powerpc_sys_##sname(const struct pt_regs *__unused)
+
+#define COND_SYSCALL(name) \
+ long __powerpc_sys_##name(const struct pt_regs *regs); \
+ asmlinkage long __weak __powerpc_sys_##name(const struct pt_regs *regs) \
+ { \
+ return sys_ni_syscall(); \
+ }
+
+#define SYS_NI(name) SYSCALL_ALIAS(__powerpc_sys_##name, sys_ni_posix_timers);
+
+#endif /* __ASM_SYSCALL_WRAPPER_H */
diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index fbeab8e88c5e..7b66f9fdfa04 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -15,6 +15,12 @@
#include <asm/unistd.h>
#include <asm/ucontext.h>
+#ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+asmlinkage long sys_ni_syscall(void);
+#else
+asmlinkage long sys_ni_syscall(const struct pt_regs *regs);
+#endif
+
struct rtas_args;
#ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
@@ -24,7 +30,6 @@ struct rtas_args;
*/
asmlinkage long sys_rtas(struct rtas_args __user *uargs);
-asmlinkage long sys_ni_syscall(void);
#ifdef CONFIG_PPC64
asmlinkage long sys_ppc64_personality(unsigned long personality);
@@ -95,6 +100,24 @@ asmlinkage long compat_sys_ppc_sync_file_range2(int fd, unsigned int flags,
unsigned int nbytes2);
#endif /* CONFIG_COMPAT */
+#else
+
+#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native)
+#define __SYSCALL(nr, entry) \
+ asmlinkage long __powerpc_##entry(const struct pt_regs *regs);
+
+#ifdef CONFIG_PPC64
+#include <asm/syscall_table_64.h>
+#else
+#include <asm/syscall_table_32.h>
+#endif /* CONFIG_PPC64 */
+
+#ifdef CONFIG_COMPAT
+#undef __SYSCALL_WITH_COMPAT
+#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, compat)
+#include <asm/syscall_table_32.h>
+#endif /* CONFIG_COMPAT */
+
#endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */
#endif /* __KERNEL__ */
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 1d599df6f169..be66040f7708 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -121,9 +121,9 @@ transfer_to_syscall:
SAVE_NVGPRS(r1)
kuep_lock
- /* Calling convention has r9 = orig r0, r10 = regs */
- addi r10,r1,STACK_FRAME_OVERHEAD
- mr r9,r0
+ /* Calling convention has r3 = orig r0, r4 = regs */
+ addi r4,r1,STACK_FRAME_OVERHEAD
+ mr r3,r0
bl system_call_exception
ret_from_syscall:
diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
index 62e636e0f684..faa94a7e1edc 100644
--- a/arch/powerpc/kernel/interrupt.c
+++ b/arch/powerpc/kernel/interrupt.c
@@ -72,15 +72,13 @@ static notrace __always_inline bool prep_irq_for_enabled_exit(bool restartable)
}
/* Has to run notrace because it is entered not completely "reconciled" */
-notrace long system_call_exception(long r3, long r4, long r5,
- long r6, long r7, long r8,
- unsigned long r0, struct pt_regs *regs)
+notrace long system_call_exception(unsigned long r0, struct pt_regs *regs)
{
syscall_fn f;
kuap_lock();
- regs->orig_gpr3 = r3;
+ regs->orig_gpr3 = regs->gpr[3];
if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
@@ -194,12 +192,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
r0 = do_syscall_trace_enter(regs);
if (unlikely(r0 >= NR_syscalls))
return regs->gpr[3];
- r3 = regs->gpr[3];
- r4 = regs->gpr[4];
- r5 = regs->gpr[5];
- r6 = regs->gpr[6];
- r7 = regs->gpr[7];
- r8 = regs->gpr[8];
} else if (unlikely(r0 >= NR_syscalls)) {
if (unlikely(trap_is_unsupported_scv(regs))) {
@@ -216,18 +208,23 @@ notrace long system_call_exception(long r3, long r4, long r5,
if (unlikely(is_compat_task())) {
f = (void *)compat_sys_call_table[r0];
- r3 &= 0x00000000ffffffffULL;
- r4 &= 0x00000000ffffffffULL;
- r5 &= 0x00000000ffffffffULL;
- r6 &= 0x00000000ffffffffULL;
- r7 &= 0x00000000ffffffffULL;
- r8 &= 0x00000000ffffffffULL;
+ regs->gpr[3] &= 0x00000000ffffffffULL;
+ regs->gpr[4] &= 0x00000000ffffffffULL;
+ regs->gpr[5] &= 0x00000000ffffffffULL;
+ regs->gpr[6] &= 0x00000000ffffffffULL;
+ regs->gpr[7] &= 0x00000000ffffffffULL;
+ regs->gpr[8] &= 0x00000000ffffffffULL;
} else {
f = (void *)sys_call_table[r0];
}
- return f(r3, r4, r5, r6, r7, r8);
+ #ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+ return f(regs);
+ #else
+ return f(regs->gpr[3], regs->gpr[4], regs->gpr[5],
+ regs->gpr[6], regs->gpr[7], regs->gpr[8]);
+ #endif
}
static notrace void booke_load_dbcr0(void)
diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index ce25b28cf418..3e8a811e09c4 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -91,9 +91,9 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
li r11,\trapnr
std r11,_TRAP(r1)
std r12,_CCR(r1)
- addi r10,r1,STACK_FRAME_OVERHEAD
+ addi r4,r1,STACK_FRAME_OVERHEAD
ld r11,exception_marker at toc(r2)
- std r11,-16(r10) /* "regshere" marker */
+ std r11,-16(r4) /* "regshere" marker */
BEGIN_FTR_SECTION
HMT_MEDIUM
@@ -108,8 +108,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
* but this is the best we can do.
*/
- /* Calling convention has r9 = orig r0, r10 = regs */
- mr r9,r0
+ /* Calling convention has r3 = orig r0, r4 = regs */
+ mr r3,r0
bl system_call_exception
.Lsyscall_vectored_\name\()_exit:
@@ -275,9 +275,9 @@ END_BTB_FLUSH_SECTION
std r10,_LINK(r1)
std r11,_TRAP(r1)
std r12,_CCR(r1)
- addi r10,r1,STACK_FRAME_OVERHEAD
+ addi r4,r1,STACK_FRAME_OVERHEAD
ld r11,exception_marker at toc(r2)
- std r11,-16(r10) /* "regshere" marker */
+ std r11,-16(r4) /* "regshere" marker */
#ifdef CONFIG_PPC_BOOK3S
li r11,1
@@ -298,8 +298,8 @@ END_BTB_FLUSH_SECTION
wrteei 1
#endif
- /* Calling convention has r9 = orig r0, r10 = regs */
- mr r9,r0
+ /* Calling convention has r3 = orig r0, r4 = regs */
+ mr r3,r0
bl system_call_exception
.Lsyscall_exit:
@@ -343,16 +343,8 @@ END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
cmpdi r3,0
bne .Lsyscall_restore_regs
/* Zero volatile regs that may contain sensitive kernel data */
- li r0,0
- li r4,0
- li r5,0
- li r6,0
- li r7,0
- li r8,0
- li r9,0
- li r10,0
- li r11,0
- li r12,0
+ NULLIFY_GPR(0)
+ NULLIFY_GPRS(4, 12)
mtctr r0
mtspr SPRN_XER,r0
.Lsyscall_restore_regs_cont:
@@ -378,7 +370,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
REST_NVGPRS(r1)
mtctr r3
mtspr SPRN_XER,r4
- ld r0,GPR0(r1)
+ REST_GPR(0, r1)
REST_GPRS(4, 12, r1)
b .Lsyscall_restore_regs_cont
.Lsyscall_rst_end:
diff --git a/arch/powerpc/kernel/systbl.c b/arch/powerpc/kernel/systbl.c
index b88a9c2a1f50..cb05e302ea58 100644
--- a/arch/powerpc/kernel/systbl.c
+++ b/arch/powerpc/kernel/systbl.c
@@ -15,8 +15,10 @@
#include <asm/unistd.h>
#include <asm/syscalls.h>
+#undef __SYSCALL_WITH_COMPAT
#define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
+#undef __SYSCALL
#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
#define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
#define __powerpc_sys_ni_syscall sys_ni_syscall
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 080c9e7de0c0..900dc8ed1f14 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -39,6 +39,8 @@
extern char vdso32_start, vdso32_end;
extern char vdso64_start, vdso64_end;
+asmlinkage long sys_ni_syscall(void);
+
/*
* The vdso data page (aka. systemcfg for old ppc64 fans) is here.
* Once the early boot kernel code no longer needs to muck around
--
2.34.1
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