Clear registers after system calls.
This commit is contained in:
Jonas 'Sortie' Termansen
parent
33c7f48909
commit
0fc3d70716
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@ -617,6 +617,7 @@ retry_another_signal:
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intctx->cs = UCS | URPL;
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intctx->ds = UDS | URPL;
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intctx->ss = UDS | URPL;
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intctx->ebx = 0;
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#elif defined(__x86_64__)
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intctx->rip = intctx->rdi;
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intctx->rflags = intctx->rsi;
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@ -624,6 +625,9 @@ retry_another_signal:
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intctx->cs = UCS | URPL;
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intctx->ds = UDS | URPL;
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intctx->ss = UDS | URPL;
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intctx->rdi = 0;
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intctx->rsi = 0;
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intctx->r8 = 0;
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#else
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#error "You may need to fix the registers"
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#endif
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@ -1,6 +1,6 @@
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/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2014.
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2014, 2015.
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This file is part of Sortix.
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@ -36,9 +36,9 @@ syscall_handler:
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# Make sure the requested system call is valid, if not, then fix it.
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cmp $SYSCALL_MAX_NUM, %rax
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jae fix_syscall
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jae 3f
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valid_syscall:
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1:
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# Read a system call function pointer.
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xorq %r11, %r11
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movq syscall_list(%r11,%rax,8), %rax
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@ -52,19 +52,33 @@ valid_syscall:
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popq %rbp
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movl global_errno, %ecx
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# Zero registers to avoid information leaks.
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# rax is return value.
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# rdi is set in a moment.
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xor %rsi, %rsi
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# rdx is return value (MIGHT NOT BE INITIALIZED, CAN LEAK!).
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# rcx is errno.
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xor %r8, %r8
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xor %r9, %r9
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xor %r10, %r10
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xor %r11, %r11
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# The rest of the registers are preserved by the ABI and syscall ABI.
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# If any signals are pending, fire them now.
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movq asm_signal_is_pending, %rdi
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testq %rdi, %rdi
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jnz call_signal_dispatcher
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jnz 4f
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# rdi is zero in this branch.
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2:
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iretq
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fix_syscall:
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3:
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# Call the null system call instead.
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xorq %rax, %rax
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jmp valid_syscall
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jmp 1b
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call_signal_dispatcher:
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4:
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# We can't return to this location after the signal, since if any system
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# call is made this stack will get reused and all our nice temporaries wil
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# be garbage. We therefore pass the kernel the state to return to and it'll
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@ -74,7 +88,11 @@ call_signal_dispatcher:
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movq 24(%rsp), %r8 # userspace rsp, note %rcx is used for errno
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int $130 # Deliver pending signals.
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# If we end up here, it means that the signal didn't override anything and
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# that we should just go ahead and return to userspace ourselves.
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iretq
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# that we should just go ahead and return to userspace ourselves. Zero the
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# scratch registers to avoid information leaks.
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xor %rdi, %rdi
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xor %rsi, %rsi
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xor %r8, %r8
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jmp 2b
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.size syscall_handler, .-syscall_handler
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@ -1,6 +1,6 @@
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/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2014.
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2014, 2015.
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This file is part of Sortix.
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@ -45,9 +45,9 @@ syscall_handler:
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# Make sure the requested system call is valid.
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cmp $SYSCALL_MAX_NUM, %eax
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jae fix_syscall
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jae 3f
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valid_syscall:
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1:
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# Read a system call function pointer.
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xorl %ebp, %ebp
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movl syscall_list(%ebp,%eax,4), %eax
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@ -76,19 +76,28 @@ valid_syscall:
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popl %ebp
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movl global_errno, %ecx
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# Zero registers to avoid information leaks.
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# eax is the return value.
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# ecx is errno.
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# edx is the return value (MIGHT NOT BE INITIALIZED, CAN LEAK!).
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# ebx is set in a moment.
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xor %esi, %esi
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xor %edi, %edi
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# If any signals are pending, fire them now.
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movl asm_signal_is_pending, %ebx
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testl %ebx, %ebx
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jnz call_signal_dispatcher
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jnz 4f
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# ebx is zero in this branch.
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2:
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iretl
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fix_syscall:
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3:
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# Call the null system call instead.
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xorl %eax, %eax
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jmp valid_syscall
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jmp 1b
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call_signal_dispatcher:
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4:
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# We can't return to this location after the signal, since if any system
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# call is made this stack will get reused and all our nice temporaries wil
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# be garbage. We therefore pass the kernel the state to return to and it'll
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@ -97,6 +106,7 @@ call_signal_dispatcher:
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int $130 # Deliver pending signals.
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# If we end up here, it means that the signal didn't override anything and
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# that we should just go ahead and return to userspace ourselves.
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iretl
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xor %ebx, %ebx
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jmp 2b
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.size syscall_handler, .-syscall_handler
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