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Kernel: Use ksyms in-place instead of duplicating them into eternal heap

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We can leave the .ksyms section mapped-but-read-only and then have the
symbols index simply point into it.

Note that we manually insert null-terminators into the symbols section
while parsing it.

This gets rid of ~950 KiB of kmalloc_eternal() at startup. :^)
This commit is contained in:
Andreas Kling 2021-12-17 09:52:06 +01:00
parent abf2204402
commit 1f2d0d0ad4
4 changed files with 11 additions and 13 deletions
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11
Kernel/KSyms.cpp
View file

@ -54,12 +54,12 @@ const KernelSymbol* symbolicate_kernel_address(FlatPtr address)
return nullptr;
}
UNMAP_AFTER_INIT static void load_kernel_symbols_from_data(ReadonlyBytes buffer)
UNMAP_AFTER_INIT static void load_kernel_symbols_from_data(Bytes buffer)
{
g_lowest_kernel_symbol_address = 0xffffffff;
g_highest_kernel_symbol_address = 0;
auto* bufptr = (const char*)buffer.data();
auto* bufptr = (char*)buffer.data();
auto* start_of_name = bufptr;
FlatPtr address = 0;
@ -84,10 +84,9 @@ UNMAP_AFTER_INIT static void load_kernel_symbols_from_data(ReadonlyBytes buffer)
}
auto& ksym = s_symbols[current_symbol_index];
ksym.address = kernel_load_base + address;
char* name = static_cast<char*>(kmalloc_eternal((bufptr - start_of_name) + 1));
memcpy(name, start_of_name, bufptr - start_of_name);
name[bufptr - start_of_name] = '\0';
ksym.name = name;
ksym.name = start_of_name;
*bufptr = '\0';
if (ksym.address < g_lowest_kernel_symbol_address)
g_lowest_kernel_symbol_address = ksym.address;

7
Kernel/Memory/MemoryManager.cpp
View file

@ -136,7 +136,7 @@ void MemoryManager::unmap_text_after_init()
dmesgln("Unmapped {} KiB of kernel text after init! :^)", (end - start) / KiB);
}
void MemoryManager::unmap_ksyms_after_init()
void MemoryManager::protect_ksyms_after_init()
{
SpinlockLocker mm_lock(s_mm_lock);
SpinlockLocker page_lock(kernel_page_directory().get_lock());
@ -144,14 +144,13 @@ void MemoryManager::unmap_ksyms_after_init()
auto start = page_round_down((FlatPtr)start_of_kernel_ksyms);
auto end = page_round_up((FlatPtr)end_of_kernel_ksyms);
// Unmap the entire .ksyms section
for (auto i = start; i < end; i += PAGE_SIZE) {
auto& pte = *ensure_pte(kernel_page_directory(), VirtualAddress(i));
pte.clear();
pte.set_writable(false);
flush_tlb(&kernel_page_directory(), VirtualAddress(i));
}
dmesgln("Unmapped {} KiB of kernel symbols after init! :^)", (end - start) / KiB);
dmesgln("Write-protected kernel symbols after init.");
}
UNMAP_AFTER_INIT void MemoryManager::register_reserved_ranges()

2
Kernel/Memory/MemoryManager.h
View file

@ -160,7 +160,7 @@ public:
void protect_readonly_after_init_memory();
void unmap_text_after_init();
void unmap_ksyms_after_init();
void protect_ksyms_after_init();
static void enter_process_address_space(Process&);
static void enter_address_space(AddressSpace&);

4
Kernel/init.cpp
View file

@ -336,8 +336,8 @@ void init_stage2(void*)
// NOTE: Everything marked UNMAP_AFTER_INIT becomes inaccessible after this point.
MM.unmap_text_after_init();
// NOTE: Everything in the .ksyms section becomes inaccessible after this point.
MM.unmap_ksyms_after_init();
// NOTE: Everything in the .ksyms section becomes read-only after this point.
MM.protect_ksyms_after_init();
// FIXME: It would be nicer to set the mode from userspace.
// FIXME: It would be smarter to not hardcode that the first tty is the only graphical one