From 3d2eb900a3f390f6969a0d477e4287dfd8ca7043 Mon Sep 17 00:00:00 2001
From: Amelia Coutard <eliottulio.coutard@gmail.com>
Date: Tue, 1 Aug 2023 06:00:06 +0200
Subject: [PATCH] Changed processes to save all (general-purpose) registers on
syscalls (except for r11 and rcx, of course). Will keep working on them later
---
doc.txt | 4 +-
kernel/src/elf64.cpp | 3 --
kernel/src/kernel.cpp | 6 ++-
kernel/src/ring3.S | 96 +++++++++++++++++++++++++++----------------
kernel/src/ring3.cpp | 4 ++
kernel/src/ring3.hpp | 30 ++++++++------
6 files changed, 88 insertions(+), 55 deletions(-)
diff --git a/doc.txt b/doc.txt
index 75829d0..307d7f8 100644
--- a/doc.txt
+++ b/doc.txt
@@ -12,8 +12,8 @@ isos documentation:
0000'7FFF'FFFF'0000 â 0000'8000'0000'0000 - stack: 64KiB
-- Invalid addresses --
FFFF'8000'0000'0000 â FFFF'C000'0000'0000 - physical memory: 64TiB
-FFFF'C000'0000'0000 â FFFF'C000'1000'0000 - process information table: 256MiB, 2048 processes, 4093 ports/process
-FFFF'C000'1000'0000 â FFFF'FFFF'8000'0000 - unmapped: 64TiB - 2GiB - 128MiB - 64KiB
+FFFF'C000'0000'0000 â ____'____'____'____ - process information table: 2048 processes, 4093 ports/process
+____'____'____'____ â FFFF'FFFF'8000'0000 - unmapped
FFFF'FFFF'8000'0000 â10000'0000'0000'0000 - kernel: 2GiB
---------------------------
diff --git a/kernel/src/elf64.cpp b/kernel/src/elf64.cpp
index acc4244..c129d07 100644
--- a/kernel/src/elf64.cpp
+++ b/kernel/src/elf64.cpp
@@ -33,7 +33,6 @@ void os::elf::load_elf(os::process& result, std::byte* start, std::size_t length
constexpr std::size_t stack_size = 16 * 0x1000 /* 64KiB */;
std::byte* const stack = (std::byte*)0x0000'8000'0000'0000 - stack_size;
- result.exists = true;
result.PML4T = phys_ptr<paging::PML4T>(os::paging::page_allocator.allocate(1).ptr.get_phys_addr());
result.rip = std::uint64_t(elf_header.entry);
result.rsp = std::uint64_t(stack + stack_size);
@@ -43,8 +42,6 @@ void os::elf::load_elf(os::process& result, std::byte* start, std::size_t length
result.r13 = 0;
result.r14 = 0;
result.r15 = 0;
- result.mxcsr = 0;
- result.x87cw = 0;
// Copy kernel mappings to the new virtual address space.
memset(result.PML4T->contents, 0, 256 * sizeof(os::paging::PML4E));
diff --git a/kernel/src/kernel.cpp b/kernel/src/kernel.cpp
index 1fd5a1c..2035138 100644
--- a/kernel/src/kernel.cpp
+++ b/kernel/src/kernel.cpp
@@ -59,6 +59,7 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
os::paging::setup_page(PML4T, (void*)0xFFFF'C000'0000'0000, 1, 0); // The startup module.
+ bool module_specified = false;
for (auto it = multiboot2::next(info); it->type != multiboot2::info::type_t::end; it = multiboot2::next(it)) {
switch (it->type) {
case multiboot2::info::type_t::memory_map:
@@ -79,7 +80,8 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
break;
case multiboot2::info::type_t::modules:
os::print("{}->{}: {}\n", multiboot2::modules_mod_start(it), multiboot2::modules_mod_end(it), multiboot2::modules_string(it));
- os::assert(!os::get_process(0).exists, "Multiple modules specified in the multiboot. This is unsupported.");
+ os::assert(!module_specified, "Multiple modules specified in the multiboot. This is unsupported.");
+ module_specified = true;
os::elf::load_elf(os::get_process(0),
(std::byte*)multiboot2::modules_mod_start(it),
multiboot2::modules_mod_end(it) - multiboot2::modules_mod_start(it),
@@ -89,7 +91,7 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
}
}
- os::assert(os::get_process(0).exists, "No modules specified in the multiboot. This is unsupported.");
+ os::assert(module_specified, "No modules specified in the multiboot. This is unsupported.");
// kernel_start and kernel_end are aligned to 4K by the linker script.
const os::phys_ptr<os::paging::page> kernel_s = ([]() {
diff --git a/kernel/src/ring3.S b/kernel/src/ring3.S
index dd23354..5551cff 100644
--- a/kernel/src/ring3.S
+++ b/kernel/src/ring3.S
@@ -37,45 +37,53 @@ load_tss:
.globl syscall_64bit_handler
syscall_64bit_handler:
- mov %rax, rax_save
- movq current_pid, %rax
- shl $17, %rax # * 0x1000 * 32 (i.e. the size of a process)
- addq process_struct_table, %rax
- # %rax now contains the address of the current process struct.
- movq %rcx, 0x10(%rax) # %rip
- movq %rbx, 0x18(%rax)
- movq %rsp, 0x20(%rax)
- movq %rbp, 0x28(%rax)
- movq %r12, 0x30(%rax)
- movq %r13, 0x38(%rax)
- movq %r14, 0x40(%rax)
- movq %r15, 0x48(%rax)
- fstcw 0x58(%rax)
- # Current process registers have now all been saved.
- mov rax_save, %rax
-
- mov %r10, %rcx
+ # Save all registers:
+ .irp reg,rax,rbx,rcx,rdx,rsp,rbp,rsi,rdi,r8,r9,r10,r11,r12,r13,r14,r15
+ mov %\reg, save_reg_tmp_\reg
+ .endr
+ # Setup stack:
+ mov $stack_top, %rsp
+ # Get process data location:
+ mov current_pid, %rdi
+ call get_process
+ # Really save all regs:
+ .irp reg,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
+ mov save_regs_tmp + \reg * 8, %rbx # Get %r\reg
+ mov %rbx, 8 + \reg * 8(%rax) # And store it.
+ .endr
+ mov save_reg_tmp_rcx, %rbx # Save the rip also.
+ mov %rbx, 0x88(%rax)
+ # Get ready for syscall:
+ mov save_reg_tmp_rdi, %rdi
+ mov save_reg_tmp_rsi, %rsi
+ mov save_reg_tmp_rdx, %rdx
+ mov save_reg_tmp_r10, %rcx # Syscall ABI -> C ABI
+ mov save_reg_tmp_r8, %r8
+ mov save_reg_tmp_r9, %r9
+ mov save_reg_tmp_rax, %rax
cmp $syscall_n, %rax
- mov $stack_top, %rsp # Setup stack
jae incorrect_syscall
callq *syscalls_call_table(, %rax, 8)
syscall_end:
- mov %rax, rax_save
- movq current_pid, %rax
- shl $17, %rax # * 0x1000 * 32 (i.e. the size of a process)
- addq process_struct_table, %rax
- # %rax now contains the address of the current process struct.
- movq 0x10(%rax), %rcx # %rip
- movq 0x18(%rax), %rbx
- movq 0x20(%rax), %rsp
- movq 0x28(%rax), %rbp
- movq 0x30(%rax), %r12
- movq 0x38(%rax), %r13
- movq 0x40(%rax), %r14
- movq 0x48(%rax), %r15
- fldcw 0x58(%rax)
- # Current process registers have now all been loaded.
- mov rax_save, %rax
+ mov %rax, %rbp # Save the return
+ mov %rdx, %rbx # registers.
+ # Get process data location:
+ mov current_pid, %rdi
+ call get_process
+ # Restore all regs:
+ .irp reg,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15
+ mov 8 + \reg * 8(%rax), %rbx # Get %r\reg
+ mov %rbx, save_regs_tmp + \reg * 8 # And restore it.
+ .endr
+ mov %rbp, save_reg_tmp_rax # Restore the return
+ mov %rbx, save_reg_tmp_rdx # registers as well.
+ mov 0x88(%rax), %rbx # Save the rip in place of rcx, because this is sysret.
+ mov %rbx, save_reg_tmp_rcx
+ # Really restore all regs:
+ .irp reg,rax,rbx,rcx,rdx,rsp,rbp,rsi,rdi,r8,r9,r10,r11,r12,r13,r14,r15
+ mov save_reg_tmp_\reg, %\reg
+ .endr
+ # Current process registers have now all been restored.
sysretq
incorrect_syscall:
call syscall_rax_error_handler
@@ -90,4 +98,20 @@ syscalls_call_table:
process_struct_table: .quad 0xFFFFC00000000000
.section .data
-rax_save: .quad 1
+save_regs_tmp:
+save_reg_tmp_rax: .quad 1
+save_reg_tmp_rbx: .quad 1
+save_reg_tmp_rcx: .quad 1
+save_reg_tmp_rdx: .quad 1
+save_reg_tmp_rsp: .quad 1
+save_reg_tmp_rbp: .quad 1
+save_reg_tmp_rsi: .quad 1
+save_reg_tmp_rdi: .quad 1
+save_reg_tmp_r8: .quad 1
+save_reg_tmp_r9: .quad 1
+save_reg_tmp_r10: .quad 1
+save_reg_tmp_r11: .quad 1
+save_reg_tmp_r12: .quad 1
+save_reg_tmp_r13: .quad 1
+save_reg_tmp_r14: .quad 1
+save_reg_tmp_r15: .quad 1
diff --git a/kernel/src/ring3.cpp b/kernel/src/ring3.cpp
index 847cbaf..c8b8400 100644
--- a/kernel/src/ring3.cpp
+++ b/kernel/src/ring3.cpp
@@ -69,4 +69,8 @@ extern "C" void os::syscall_rax_error_handler() {
os::assert(false, "Incorrect %rax for syscall.");
}
+os::process& os::get_process(std::uint64_t pid) {
+ os::assert(pid < 2048, "Invalid pid: {}.\n", pid);
+ return ((process*)0xFFFF'C000'0000'0000)[pid];
+}
std::uint64_t os::current_pid;
diff --git a/kernel/src/ring3.hpp b/kernel/src/ring3.hpp
index 7d26636..49069bf 100644
--- a/kernel/src/ring3.hpp
+++ b/kernel/src/ring3.hpp
@@ -61,31 +61,37 @@ struct port {
};
struct process {
- bool exists;
phys_ptr<paging::PML4T> PML4T;
- std::uint64_t rip;
+ std::uint64_t rax;
std::uint64_t rbx;
+ std::uint64_t rcx;
+ std::uint64_t rdx;
std::uint64_t rsp;
std::uint64_t rbp;
+ std::uint64_t rsi;
+ std::uint64_t rdi;
+ std::uint64_t r8;
+ std::uint64_t r9;
+ std::uint64_t r10;
+ std::uint64_t r11;
std::uint64_t r12;
std::uint64_t r13;
std::uint64_t r14;
std::uint64_t r15;
- std::uint64_t mxcsr; // UNUSED for now.
- std::uint64_t x87cw;
- port ports[4093];
+ std::uint64_t rip;
+ port ports[2043];
+ char padding[16];
};
-static_assert(sizeof(process) == 0x1000 * 32);
+static_assert(sizeof(process) == 4096 * 16);
+static_assert(0xFFFF'C000'0000'0000 + sizeof(process) * 2048 < 0xFFFF'FFFF'8000'0000);
+
+extern "C" process& get_process(std::uint64_t pid);
-inline process& get_process(std::uint64_t pid) {
- os::assert(pid < 2048, "Invalid pid: {}.\n", pid);
- return ((process*)0xFFFF'C000'0000'0000)[pid];
-}
inline bool process_exists(std::uint64_t pid) {
- return pid < 2048 && get_process(pid).exists;
+ return pid < 2048;
}
inline bool port_exists(std::uint64_t pid, std::uint64_t port) {
- return port < 4093 && process_exists(pid) && get_process(pid).ports[port].exists;
+ return port < 2043 && process_exists(pid) && get_process(pid).ports[port].exists;
}
extern "C" std::uint64_t current_pid;
--
2.46.0