[PATCH v2 3/3] sh: don't pass saved userspace state to exception handlers

[Bobby Bingham]

The compiler is permitted to generate code which overwrites the parameters
to a function. If those parameters include the only saved copy we have of
userspace's registers, we're in trouble.

Signed-off-by: Bobby Bingham <koor...@koorogi.info>
---
 arch/sh/include/asm/traps_32.h | 16 ++++------------
 arch/sh/kernel/traps_32.c      | 23 +++++++----------------
 2 files changed, 11 insertions(+), 28 deletions(-)

diff --git a/arch/sh/include/asm/traps_32.h b/arch/sh/include/asm/traps_32.h
index cfd55ff..17e129f 100644
--- a/arch/sh/include/asm/traps_32.h
+++ b/arch/sh/include/asm/traps_32.h
@@ -42,18 +42,10 @@ static inline void trigger_address_error(void)
 asmlinkage void do_address_error(struct pt_regs *regs,
                                 unsigned long writeaccess,
                                 unsigned long address);
-asmlinkage void do_divide_error(unsigned long r4, unsigned long r5,
-                               unsigned long r6, unsigned long r7,
-                               struct pt_regs __regs);
-asmlinkage void do_reserved_inst(unsigned long r4, unsigned long r5,
-                               unsigned long r6, unsigned long r7,
-                               struct pt_regs __regs);
-asmlinkage void do_illegal_slot_inst(unsigned long r4, unsigned long r5,
-                               unsigned long r6, unsigned long r7,
-                               struct pt_regs __regs);
-asmlinkage void do_exception_error(unsigned long r4, unsigned long r5,
-                                  unsigned long r6, unsigned long r7,
-                                  struct pt_regs __regs);
+asmlinkage void do_divide_error(unsigned long r4);
+asmlinkage void do_reserved_inst(void);
+asmlinkage void do_illegal_slot_inst(void);
+asmlinkage void do_exception_error(void);
 
 #define BUILD_TRAP_HANDLER(name)                                       \
 asmlinkage void name##_trap_handler(unsigned long r4, unsigned long r5,        
\
diff --git a/arch/sh/kernel/traps_32.c b/arch/sh/kernel/traps_32.c
index 68e99f0..ff63934 100644
--- a/arch/sh/kernel/traps_32.c
+++ b/arch/sh/kernel/traps_32.c
@@ -594,9 +594,7 @@ int is_dsp_inst(struct pt_regs *regs)
 #endif /* CONFIG_SH_DSP */
 
 #ifdef CONFIG_CPU_SH2A
-asmlinkage void do_divide_error(unsigned long r4, unsigned long r5,
-                               unsigned long r6, unsigned long r7,
-                               struct pt_regs __regs)
+asmlinkage void do_divide_error(unsigned long r4)
 {
        siginfo_t info;
 
@@ -613,11 +611,9 @@ asmlinkage void do_divide_error(unsigned long r4, unsigned 
long r5,
 }
 #endif
 
-asmlinkage void do_reserved_inst(unsigned long r4, unsigned long r5,
-                               unsigned long r6, unsigned long r7,
-                               struct pt_regs __regs)
+asmlinkage void do_reserved_inst(void)
 {
-       struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
+       struct pt_regs *regs = current_pt_regs();
        unsigned long error_code;
        struct task_struct *tsk = current;
 
@@ -701,11 +697,9 @@ static int emulate_branch(unsigned short inst, struct 
pt_regs *regs)
 }
 #endif
 
-asmlinkage void do_illegal_slot_inst(unsigned long r4, unsigned long r5,
-                               unsigned long r6, unsigned long r7,
-                               struct pt_regs __regs)
+asmlinkage void do_illegal_slot_inst(void)
 {
-       struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
+       struct pt_regs *regs = current_pt_regs();
        unsigned long inst;
        struct task_struct *tsk = current;
 
@@ -730,15 +724,12 @@ asmlinkage void do_illegal_slot_inst(unsigned long r4, 
unsigned long r5,
        die_if_no_fixup("illegal slot instruction", regs, inst);
 }
 
-asmlinkage void do_exception_error(unsigned long r4, unsigned long r5,
-                                  unsigned long r6, unsigned long r7,
-                                  struct pt_regs __regs)
+asmlinkage void do_exception_error(void)
 {
-       struct pt_regs *regs = RELOC_HIDE(&__regs, 0);
        long ex;
 
        ex = lookup_exception_vector();
-       die_if_kernel("exception", regs, ex);
+       die_if_kernel("exception", current_pt_regs(), ex);
 }
 
 void per_cpu_trap_init(void)
-- 
1.8.5.5

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