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Kernel+LibC+crash: Add mprotect() syscall

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This patch adds the mprotect() syscall to allow changing the protection
flags for memory regions. We don't do any region splitting/merging yet,
so this only works on whole mmap() regions.

Added a "crash -r" flag to verify that we crash when you attempt to
write to read-only memory. :^)
This commit is contained in:
Andreas Kling 2019-08-12 19:33:24 +02:00
parent 4917445e2e
commit 7d6689055f
7 changed files with 36 additions and 1 deletions
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10
Kernel/Process.cpp
View file

@ -224,6 +224,16 @@ int Process::sys$munmap(void* addr, size_t size)
return 0;
}
int Process::sys$mprotect(void* addr, size_t size, int prot)
{
auto* region = region_from_range(VirtualAddress((u32)addr), size);
if (!region)
return -EINVAL;
region->set_writable(prot & PROT_WRITE);
MM.remap_region(page_directory(), *region);
return 0;
}
int Process::sys$gethostname(char* buffer, ssize_t size)
{
if (size < 0)

1
Kernel/Process.h
View file

@ -145,6 +145,7 @@ public:
void* sys$mmap(const Syscall::SC_mmap_params*);
int sys$munmap(void*, size_t size);
int sys$set_mmap_name(void*, size_t, const char*);
int sys$mprotect(void*, size_t, int prot);
int sys$select(const Syscall::SC_select_params*);
int sys$poll(pollfd*, int nfds, int timeout);
ssize_t sys$get_dir_entries(int fd, void*, ssize_t);

2
Kernel/Syscall.cpp
View file

@ -305,6 +305,8 @@ static u32 handle(RegisterDump& regs, u32 function, u32 arg1, u32 arg2, u32 arg3
return current->process().sys$share_buffer_globally((int)arg1);
case Syscall::SC_set_process_icon:
return current->process().sys$set_process_icon((int)arg1);
case Syscall::SC_mprotect:
return current->process().sys$mprotect((void*)arg1, (size_t)arg2, (int)arg3);
default:
kprintf("<%u> int0x82: Unknown function %u requested {%x, %x, %x}\n", current->process().pid(), function, arg1, arg2, arg3);
return -ENOSYS;

3
Kernel/Syscall.h
View file

@ -122,7 +122,8 @@ struct timeval;
__ENUMERATE_SYSCALL(dbgputstr) \
__ENUMERATE_SYSCALL(watch_file) \
__ENUMERATE_SYSCALL(share_buffer_globally) \
__ENUMERATE_SYSCALL(set_process_icon)
__ENUMERATE_SYSCALL(set_process_icon) \
__ENUMERATE_SYSCALL(mprotect)
namespace Syscall {