From 2cfcba7e6ed64a00ca01dcc7247ecfc5edacfdb2 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Wed, 13 Mar 2024 21:08:50 -0400
Subject: kernel: sched: Improve stack init code
Signed-off-by: Ian Moffett <ian@osmora.org>
---
sys/include/sys/loader.h | 27 +++++----
sys/kern/kern_sched.c | 139 +++++++++++++++++++++++++----------------------
2 files changed, 91 insertions(+), 75 deletions(-)
diff --git a/sys/include/sys/loader.h b/sys/include/sys/loader.h
index c1aa426..74a325c 100644
--- a/sys/include/sys/loader.h
+++ b/sys/include/sys/loader.h
@@ -33,17 +33,22 @@
#include <sys/types.h>
#include <vm/pmap.h>
-#define AT_NULL 0
-#define AT_IGNORE 1
-#define AT_EXECFD 2
-#define AT_PHDR 3
-#define AT_PHENT 4
-#define AT_PHNUM 5
-#define AT_PAGESZ 6
-#define AT_BASE 7
-#define AT_FLAGS 8
-#define AT_ENTRY 9
-#define AT_SECURE 10
+/* DANGER!: DO NOT CHANGE THESE DEFINES */
+#define AT_NULL 0
+#define AT_ENTRY 1
+#define AT_PHDR 2
+#define AT_PHENT 3
+#define AT_PHNUM 4
+#define AT_EXECPATH 5
+#define AT_SECURE 6
+#define AT_RANDOM 7
+#define AT_EXECFN 8
+
+#define STACK_PUSH(ptr, val) *(--ptr) = val
+#define AUXVAL(ptr, tag, val) __extension__ ({ \
+ STACK_PUSH(ptr, val); \
+ STACK_PUSH(ptr, tag); \
+});
/* Auxiliary Vector */
struct auxval {
diff --git a/sys/kern/kern_sched.c b/sys/kern/kern_sched.c
index 9231ea2..7be8241 100644
--- a/sys/kern/kern_sched.c
+++ b/sys/kern/kern_sched.c
@@ -48,6 +48,20 @@
#define STACK_PAGES 8
#define STACK_SIZE (STACK_PAGES*vm_get_page_size())
+/*
+ * The PHYS_TO_VIRT/VIRT_TO_PHYS macros convert
+ * addresses to lower and higher half addresses.
+ * Userspace addresses are on the lower half,
+ * therefore, we can just wrap over these to
+ * keep things simple.
+ *
+ * XXX: TODO: This won't work when not identity mapping
+ * lowerhalf addresses. Once that is updated,
+ * get rid of this.
+ */
+#define USER_TO_KERN(user) PHYS_TO_VIRT(user)
+#define KERN_TO_USER(kern) VIRT_TO_PHYS(kern)
+
/*
* Thread ready queue - all threads ready to be
* scheduled should be added to this queue.
@@ -133,86 +147,87 @@ static uintptr_t
sched_init_stack(void *stack_top, char *argvp[], char *envp[], struct auxval auxv)
{
uintptr_t *sp = stack_top;
- size_t envp_len, argv_len, len;
- uintptr_t old_sp = 0;
- uintptr_t ret;
-
- for (envp_len = 0; envp[envp_len] != NULL; ++envp_len) {
- len = strlen(envp[envp_len]);
- sp = (void *)((uintptr_t)sp - len - 1);
- memcpy(sp, envp[envp_len], len);
+ void *env_ptr = NULL, *argv_ptr = NULL;
+ size_t argc, envc, len;
+
+ /* Copy argument and environment strings */
+ for (envc = 0; envp[envc] != NULL; ++envc) {
+ len = strlen(envp[envc]);
+ sp -= len - 1;
+ memcpy(sp, envp[envc], len);
}
- for (argv_len = 0; argvp[argv_len] != NULL; ++argv_len) {
- len = strlen(argvp[argv_len]);
- sp = (void *)((uintptr_t)sp - len - 1);
- memcpy(sp, argvp[envp_len], len);
- }
+ __assert(envc >= 1);
+ env_ptr = sp;
- sp = (uint64_t *)(((uintptr_t)sp / 16) * 16);
- if (((argv_len + envp_len + 1) & 1) != 0) {
- sp--;
+ for (argc = 0; argvp[argc] != NULL; ++argc) {
+ len = strlen(argvp[argc]);
+ sp -= len - 1;
+ memcpy(sp, argvp[argc], len);
}
- *--sp = 0;
- *--sp = 0;
- *--sp = auxv.at_entry;
- *--sp = AT_ENTRY;
- *--sp = auxv.at_phent;
- *--sp = AT_PHENT;
- *--sp = auxv.at_phnum;
- *--sp = AT_PHNUM;
- *--sp = auxv.at_phdr;
- *--sp = AT_PHDR;
-
- old_sp = (uintptr_t)sp;
-
- /* End of envp */
- *--sp = 0;
- sp -= envp_len;
- for (int i = 0; i < envp_len; ++i) {
- old_sp -= strlen(envp[i]) + 1;
- sp[i] = old_sp;
+ __assert(argc >= 1);
+ argv_ptr = sp;
+
+ /* Ensure the stack is aligned */
+ sp = (void *)__ALIGN_DOWN((uintptr_t)sp, 16);
+ if (((argc + envc + 1) & 1) != 0)
+ --sp;
+
+ AUXVAL(sp, AT_NULL, 0x0);
+ AUXVAL(sp, AT_SECURE, 0x0);
+ AUXVAL(sp, AT_ENTRY, auxv.at_entry);
+ AUXVAL(sp, AT_PHDR, auxv.at_phdr);
+ AUXVAL(sp, AT_PHNUM, auxv.at_phnum);
+ STACK_PUSH(sp, 0);
+
+ /* Push environment string pointers */
+ for (int i = 0; i < envc; ++i) {
+ len = strlen(env_ptr);
+ sp -= len;
+
+ *sp = (uintptr_t)KERN_TO_USER((uintptr_t)env_ptr);
+ env_ptr = (char *)env_ptr + len;
}
- /* End of argvp */
- *--sp = 0;
- sp -= argv_len;
- for (int i = 0; i < argv_len; ++i) {
- old_sp -= strlen(argvp[i]) + 1;
- sp[i] = old_sp;
+ /* Push argument string pointers */
+ STACK_PUSH(sp, 0);
+ for (int i = 0; i < argc; ++i) {
+ len = strlen(argv_ptr);
+ sp -= len;
+
+ *sp = (uintptr_t)KERN_TO_USER((uintptr_t)argv_ptr);
+ argv_ptr = (char *)argv_ptr + len;
}
- /* Argc */
- *--sp = argv_len;
+ STACK_PUSH(sp, argc);
- ret = (uintptr_t)stack_top;
- ret -= (ret - (uintptr_t)sp);
- return ret;
+ return (uintptr_t)sp;
}
static uintptr_t
-sched_create_stack(struct vas vas, bool user)
+sched_create_stack(struct vas vas, bool user, char *argvp[],
+ char *envp[], struct auxval auxv)
{
int status;
- uintptr_t user_stack;
+ uintptr_t stack;
const vm_prot_t USER_STACK_PROT = PROT_WRITE | PROT_USER;
if (!user) {
- return (uintptr_t)dynalloc(STACK_SIZE);
+ stack = (uintptr_t)dynalloc(STACK_SIZE);
+ return sched_init_stack((void *)(stack + STACK_SIZE), argvp, envp, auxv);
}
- user_stack = vm_alloc_pageframe(STACK_PAGES);
-
- status = vm_map_create(vas, user_stack, user_stack, USER_STACK_PROT,
- STACK_SIZE);
+ stack = vm_alloc_pageframe(STACK_PAGES);
+ status = vm_map_create(vas, stack, stack, USER_STACK_PROT, STACK_SIZE);
if (status != 0) {
return 0;
}
- memset(PHYS_TO_VIRT(user_stack), 0, STACK_SIZE);
- return user_stack;
+ memset(USER_TO_KERN(stack), 0, STACK_SIZE);
+ stack = sched_init_stack((void *)USER_TO_KERN(stack + STACK_SIZE), argvp, envp, auxv);
+ return stack;
}
static struct proc *
@@ -220,8 +235,7 @@ sched_create_td(uintptr_t rip, char *argvp[], char *envp[], struct auxval auxv,
struct vas vas, bool is_user)
{
struct proc *td;
- uintptr_t stack, sp;
- void *stack_virt;
+ uintptr_t stack;
struct trapframe *tf;
tf = dynalloc(sizeof(struct trapframe));
@@ -229,14 +243,12 @@ sched_create_td(uintptr_t rip, char *argvp[], char *envp[], struct auxval auxv,
return NULL;
}
- stack = sched_create_stack(vas, is_user);
+ stack = sched_create_stack(vas, is_user, argvp, envp, auxv);
if (stack == 0) {
dynfree(tf);
return NULL;
}
- stack_virt = (is_user) ? PHYS_TO_VIRT(stack) : (void *)stack;
-
td = dynalloc(sizeof(struct proc));
if (td == NULL) {
/* TODO: Free stack */
@@ -245,8 +257,7 @@ sched_create_td(uintptr_t rip, char *argvp[], char *envp[], struct auxval auxv,
}
memset(tf, 0, sizeof(struct trapframe));
- sp = sched_init_stack((void *)((uintptr_t)stack_virt + STACK_SIZE),
- argvp, envp, auxv);
+ memset(td, 0, sizeof(struct proc));
/* Setup process itself */
td->pid = 0; /* Don't assign PID until enqueued */
@@ -256,9 +267,9 @@ sched_create_td(uintptr_t rip, char *argvp[], char *envp[], struct auxval auxv,
/* Setup trapframe */
if (!is_user) {
- init_frame(tf, rip, sp);
+ init_frame(tf, rip, (uintptr_t)stack);
} else {
- init_frame_user(tf, rip, VIRT_TO_PHYS(sp));
+ init_frame_user(tf, rip, KERN_TO_USER(stack));
}
return td;
}
--
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