On mips any syscalls who return a value between -MAXERRNO (1133) and
-1, is considered as an error (the error flag is set and return value
is the positive value of the error number).
But some syscalls can return values between -MAXERRNO and -1 like
sys_time and sys_times. In this case the userspace return value is
-return value of the syscall and the error flag set.
This patch add a TIF_NOERROR thread flag which indicates that the
return value of a syscall is always correct.
All ABIs are updated (kernel 32 o32, kernel64 o32, kernel64 n32
and kernel64 n64).
---
arch/mips/include/asm/ptrace.h | 5 +++++
arch/mips/include/asm/thread_info.h | 2 ++
arch/mips/kernel/scall32-o32.S | 14 ++++++++++++++
arch/mips/kernel/scall64-64.S | 14 ++++++++++++++
arch/mips/kernel/scall64-n32.S | 14 ++++++++++++++
arch/mips/kernel/scall64-o32.S | 14 ++++++++++++++
6 files changed, 63 insertions(+)
diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
index 5e6cd09..51552f2 100644
--- a/arch/mips/include/asm/ptrace.h
+++ b/arch/mips/include/asm/ptrace.h
@@ -94,6 +94,11 @@ static inline void die_if_kernel(const char *str, struct pt_regs *regs)
die(str, regs);
}
+#define force_successful_syscall_return() \
+ do { \
+ set_thread_flag(TIF_NOERROR); \
+ } while(0)
+
#define current_pt_regs() \
({ \
unsigned long sp = (unsigned long)__builtin_frame_address(0); \
diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h
index 61215a3..6764fc1 100644
--- a/arch/mips/include/asm/thread_info.h
+++ b/arch/mips/include/asm/thread_info.h
@@ -116,6 +116,7 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_32BIT_ADDR 23 /* 32-bit address space (o32/n32) */
#define TIF_FPUBOUND 24 /* thread bound to FPU-full CPU set */
#define TIF_LOAD_WATCH 25 /* If set, load watch registers */
+#define TIF_NOERROR 30 /* Force successful syscall return */
#define TIF_SYSCALL_TRACE 31 /* syscall trace active */
#define _TIF_SYSCALL_TRACE (1<<TIF_SYSCALL_TRACE)
@@ -131,6 +132,7 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_32BIT_REGS (1<<TIF_32BIT_REGS)
#define _TIF_32BIT_ADDR (1<<TIF_32BIT_ADDR)
#define _TIF_FPUBOUND (1<<TIF_FPUBOUND)
+#define _TIF_NOERROR (1<<TIF_NOERROR)
#define _TIF_LOAD_WATCH (1<<TIF_LOAD_WATCH)
#define _TIF_WORK_SYSCALL_ENTRY (_TIF_NOHZ | _TIF_SYSCALL_TRACE | \
diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S
index e774bb1..4ac30ac 100644
--- a/arch/mips/kernel/scall32-o32.S
+++ b/arch/mips/kernel/scall32-o32.S
@@ -58,8 +58,22 @@ stack_done:
jalr t2 # Do The Real Thing (TM)
+ li t0, 0 # no error for negative return ?
+ lw t2, TI_FLAGS($28)
+ li t1, _TIF_NOERROR
+ and t2, t1
+ bnez t2, syscall_ret_noerror
+
li t0, -EMAXERRNO - 1 # error?
sltu t0, t0, v0
+ b syscall_ret_error
+
+syscall_ret_noerror:
+ li t1, ~_TIF_NOERROR # clear TIF_NOERROR
+ and t2, t1
+ sw t2, TI_FLAGS($28)
+
+syscall_ret_error:
sw t0, PT_R7(sp) # set error flag
beqz t0, 1f
diff --git a/arch/mips/kernel/scall64-64.S b/arch/mips/kernel/scall64-64.S
index be6627e..793ba7e 100644
--- a/arch/mips/kernel/scall64-64.S
+++ b/arch/mips/kernel/scall64-64.S
@@ -61,8 +61,22 @@ NESTED(handle_sys64, PT_SIZE, sp)
jalr t2 # Do The Real Thing (TM)
+ li t0, 0 # no error for negative return ?
+ LONG_L t2, TI_FLAGS($28)
+ li t1, _TIF_NOERROR
+ and t2, t1
+ bnez t2, syscall_ret_noerror
+
li t0, -EMAXERRNO - 1 # error?
sltu t0, t0, v0
+ b syscall_ret_error
+
+syscall_ret_noerror:
+ li t1, ~_TIF_NOERROR # clear TIF_NOERROR
+ and t2, t1
+ LONG_S t2, TI_FLAGS($28)
+
+syscall_ret_error:
sd t0, PT_R7(sp) # set error flag
beqz t0, 1f
diff --git a/arch/mips/kernel/scall64-n32.S b/arch/mips/kernel/scall64-n32.S
index cab1507..ccac0c6 100644
--- a/arch/mips/kernel/scall64-n32.S
+++ b/arch/mips/kernel/scall64-n32.S
@@ -54,8 +54,22 @@ NESTED(handle_sysn32, PT_SIZE, sp)
jalr t2 # Do The Real Thing (TM)
+ li t0, 0 # no error for negative return ?
+ LONG_L t2, TI_FLAGS($28)
+ li t1, _TIF_NOERROR
+ and t2, t1
+ bnez t2, syscall_ret_noerror
+
li t0, -EMAXERRNO - 1 # error?
sltu t0, t0, v0
+ b syscall_ret_error
+
+syscall_ret_noerror:
+ li t1, ~_TIF_NOERROR # clear TIF_NOERROR
+ and t2, t1
+ LONG_S t2, TI_FLAGS($28)
+
+syscall_ret_error:
sd t0, PT_R7(sp) # set error flag
beqz t0, 1f
diff --git a/arch/mips/kernel/scall64-o32.S b/arch/mips/kernel/scall64-o32.S
index 37605dc..b1d3d51 100644
--- a/arch/mips/kernel/scall64-o32.S
+++ b/arch/mips/kernel/scall64-o32.S
@@ -88,8 +88,22 @@ NESTED(handle_sys, PT_SIZE, sp)
jalr t2 # Do The Real Thing (TM)
+ li t0, 0 # no error for negative return ?
+ LONG_L t2, TI_FLAGS($28)
+ li t1, _TIF_NOERROR
+ and t2, t1
+ bnez t2, syscall_ret_noerror
+
li t0, -EMAXERRNO - 1 # error?
sltu t0, t0, v0
+ b syscall_ret_error
+
+syscall_ret_noerror:
+ li t1, ~_TIF_NOERROR # clear TIF_NOERROR
+ and t2, t1
+ LONG_S t2, TI_FLAGS($28)
+
+syscall_ret_error:
sd t0, PT_R7(sp) # set error flag
beqz t0, 1f
--
1.8.3.1
