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| author | Ralf Baechle <ralf@linux-mips.org> | 2015-07-08 04:49:10 +0200 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2015-07-08 05:03:30 +0200 |
| commit | 7928eb0370d1133d0d8cd2f5ddfca19c309079d5 (patch) | |
| tree | 0302124558fbad7327630babc1804aa5977e8c2f /arch/mips/kernel/scall32-o32.S | |
| parent | MIPS, CPUFREQ: Fix spelling of Institute. (diff) | |
| download | linux-7928eb0370d1133d0d8cd2f5ddfca19c309079d5.tar.xz linux-7928eb0370d1133d0d8cd2f5ddfca19c309079d5.zip | |
MIPS: O32: Do not handle require 32 bytes from the stack to be readable.
Commit 46e12c07b3b9603c60fc1d421ff18618241cb081 (MIPS: O32 / 32-bit:
Always copy 4 stack arguments.) change the O32 syscall handler to always
load four arguments from the userspace stack even for syscalls that
require fewer or no arguments to be copied. This removes a large table
from kernel space and need to maintain it. It appeared that it was ok
the implementation chosen requires 16 bytes of readable stack space
above the user stack pointer.
Turned out a few threading implementations munmap the user stack before
the thread exits resulting in errors due to the unreadable stack.
We now treat any failed load as a if the loaded value was zero and let
the actual syscall deal with the situation.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/kernel/scall32-o32.S')
| -rw-r--r-- | arch/mips/kernel/scall32-o32.S | 37 |
1 files changed, 27 insertions, 10 deletions
diff --git a/arch/mips/kernel/scall32-o32.S b/arch/mips/kernel/scall32-o32.S index 6e8de80bb446..4cc13508d967 100644 --- a/arch/mips/kernel/scall32-o32.S +++ b/arch/mips/kernel/scall32-o32.S @@ -73,10 +73,11 @@ NESTED(handle_sys, PT_SIZE, sp) .set noreorder .set nomacro -1: user_lw(t5, 16(t0)) # argument #5 from usp -4: user_lw(t6, 20(t0)) # argument #6 from usp -3: user_lw(t7, 24(t0)) # argument #7 from usp -2: user_lw(t8, 28(t0)) # argument #8 from usp +load_a4: user_lw(t5, 16(t0)) # argument #5 from usp +load_a5: user_lw(t6, 20(t0)) # argument #6 from usp +load_a6: user_lw(t7, 24(t0)) # argument #7 from usp +load_a7: user_lw(t8, 28(t0)) # argument #8 from usp +loads_done: sw t5, 16(sp) # argument #5 to ksp sw t6, 20(sp) # argument #6 to ksp @@ -85,10 +86,10 @@ NESTED(handle_sys, PT_SIZE, sp) .set pop .section __ex_table,"a" - PTR 1b,bad_stack - PTR 2b,bad_stack - PTR 3b,bad_stack - PTR 4b,bad_stack + PTR load_a4, bad_stack_a4 + PTR load_a5, bad_stack_a5 + PTR load_a6, bad_stack_a6 + PTR load_a7, bad_stack_a7 .previous lw t0, TI_FLAGS($28) # syscall tracing enabled? @@ -153,8 +154,8 @@ syscall_trace_entry: /* ------------------------------------------------------------------------ */ /* - * The stackpointer for a call with more than 4 arguments is bad. - * We probably should handle this case a bit more drastic. + * Our open-coded access area sanity test for the stack pointer + * failed. We probably should handle this case a bit more drastic. */ bad_stack: li v0, EFAULT @@ -163,6 +164,22 @@ bad_stack: sw t0, PT_R7(sp) j o32_syscall_exit +bad_stack_a4: + li t5, 0 + b load_a5 + +bad_stack_a5: + li t6, 0 + b load_a6 + +bad_stack_a6: + li t7, 0 + b load_a7 + +bad_stack_a7: + li t8, 0 + b loads_done + /* * The system call does not exist in this kernel */ |