minix/servers/rs/exec.c

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#include "inc.h"
#include <a.out.h>
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#include <assert.h>
#include <libexec.h>
#include <machine/vmparam.h>
static int do_exec(int proc_e, char *exec, size_t exec_len, char *progname,
char *frame, int frame_len);
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static int exec_restart(int proc_e, int result, vir_bytes pc);
static int read_seg(struct exec_info *execi, off_t off,
off_t seg_addr, size_t seg_bytes);
No more intel/minix segments. This commit removes all traces of Minix segments (the text/data/stack memory map abstraction in the kernel) and significance of Intel segments (hardware segments like CS, DS that add offsets to all addressing before page table translation). This ultimately simplifies the memory layout and addressing and makes the same layout possible on non-Intel architectures. There are only two types of addresses in the world now: virtual and physical; even the kernel and processes have the same virtual address space. Kernel and user processes can be distinguished at a glance as processes won't use 0xF0000000 and above. No static pre-allocated memory sizes exist any more. Changes to booting: . The pre_init.c leaves the kernel and modules exactly as they were left by the bootloader in physical memory . The kernel starts running using physical addressing, loaded at a fixed location given in its linker script by the bootloader. All code and data in this phase are linked to this fixed low location. . It makes a bootstrap pagetable to map itself to a fixed high location (also in linker script) and jumps to the high address. All code and data then use this high addressing. . All code/data symbols linked at the low addresses is prefixed by an objcopy step with __k_unpaged_*, so that that code cannot reference highly-linked symbols (which aren't valid yet) or vice versa (symbols that aren't valid any more). . The two addressing modes are separated in the linker script by collecting the unpaged_*.o objects and linking them with low addresses, and linking the rest high. Some objects are linked twice, once low and once high. . The bootstrap phase passes a lot of information (e.g. free memory list, physical location of the modules, etc.) using the kinfo struct. . After this bootstrap the low-linked part is freed. . The kernel maps in VM into the bootstrap page table so that VM can begin executing. Its first job is to make page tables for all other boot processes. So VM runs before RS, and RS gets a fully dynamic, VM-managed address space. VM gets its privilege info from RS as usual but that happens after RS starts running. . Both the kernel loading VM and VM organizing boot processes happen using the libexec logic. This removes the last reason for VM to still know much about exec() and vm/exec.c is gone. Further Implementation: . All segments are based at 0 and have a 4 GB limit. . The kernel is mapped in at the top of the virtual address space so as not to constrain the user processes. . Processes do not use segments from the LDT at all; there are no segments in the LDT any more, so no LLDT is needed. . The Minix segments T/D/S are gone and so none of the user-space or in-kernel copy functions use them. The copy functions use a process endpoint of NONE to realize it's a physical address, virtual otherwise. . The umap call only makes sense to translate a virtual address to a physical address now. . Segments-related calls like newmap and alloc_segments are gone. . All segments-related translation in VM is gone (vir2map etc). . Initialization in VM is simpler as no moving around is necessary. . VM and all other boot processes can be linked wherever they wish and will be mapped in at the right location by the kernel and VM respectively. Other changes: . The multiboot code is less special: it does not use mb_print for its diagnostics any more but uses printf() as normal, saving the output into the diagnostics buffer, only printing to the screen using the direct print functions if a panic() occurs. . The multiboot code uses the flexible 'free memory map list' style to receive the list of free memory if available. . The kernel determines the memory layout of the processes to a degree: it tells VM where the kernel starts and ends and where the kernel wants the top of the process to be. VM then uses this entire range, i.e. the stack is right at the top, and mmap()ped bits of memory are placed below that downwards, and the break grows upwards. Other Consequences: . Every process gets its own page table as address spaces can't be separated any more by segments. . As all segments are 0-based, there is no distinction between virtual and linear addresses, nor between userspace and kernel addresses. . Less work is done when context switching, leading to a net performance increase. (8% faster on my machine for 'make servers'.) . The layout and configuration of the GDT makes sysenter and syscall possible.
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static int exec_restart(int proc_e, int result, vir_bytes pc);
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/* Array of loaders for different object formats */
static struct exec_loaders {
libexec_exec_loadfunc_t load_object;
} const exec_loaders[] = {
{ libexec_load_elf },
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{ NULL }
};
New RS and new signal handling for system processes. UPDATING INFO: 20100317: /usr/src/etc/system.conf updated to ignore default kernel calls: copy it (or merge it) to /etc/system.conf. The hello driver (/dev/hello) added to the distribution: # cd /usr/src/commands/scripts && make clean install # cd /dev && MAKEDEV hello KERNEL CHANGES: - Generic signal handling support. The kernel no longer assumes PM as a signal manager for every process. The signal manager of a given process can now be specified in its privilege slot. When a signal has to be delivered, the kernel performs the lookup and forwards the signal to the appropriate signal manager. PM is the default signal manager for user processes, RS is the default signal manager for system processes. To enable ptrace()ing for system processes, it is sufficient to change the default signal manager to PM. This will temporarily disable crash recovery, though. - sys_exit() is now split into sys_exit() (i.e. exit() for system processes, which generates a self-termination signal), and sys_clear() (i.e. used by PM to ask the kernel to clear a process slot when a process exits). - Added a new kernel call (i.e. sys_update()) to swap two process slots and implement live update. PM CHANGES: - Posix signal handling is no longer allowed for system processes. System signals are split into two fixed categories: termination and non-termination signals. When a non-termination signaled is processed, PM transforms the signal into an IPC message and delivers the message to the system process. When a termination signal is processed, PM terminates the process. - PM no longer assumes itself as the signal manager for system processes. It now makes sure that every system signal goes through the kernel before being actually processes. The kernel will then dispatch the signal to the appropriate signal manager which may or may not be PM. SYSLIB CHANGES: - Simplified SEF init and LU callbacks. - Added additional predefined SEF callbacks to debug crash recovery and live update. - Fixed a temporary ack in the SEF init protocol. SEF init reply is now completely synchronous. - Added SEF signal event type to provide a uniform interface for system processes to deal with signals. A sef_cb_signal_handler() callback is available for system processes to handle every received signal. A sef_cb_signal_manager() callback is used by signal managers to process system signals on behalf of the kernel. - Fixed a few bugs with memory mapping and DS. VM CHANGES: - Page faults and memory requests coming from the kernel are now implemented using signals. - Added a new VM call to swap two process slots and implement live update. - The call is used by RS at update time and in turn invokes the kernel call sys_update(). RS CHANGES: - RS has been reworked with a better functional decomposition. - Better kernel call masks. com.h now defines the set of very basic kernel calls every system service is allowed to use. This makes system.conf simpler and easier to maintain. In addition, this guarantees a higher level of isolation for system libraries that use one or more kernel calls internally (e.g. printf). - RS is the default signal manager for system processes. By default, RS intercepts every signal delivered to every system process. This makes crash recovery possible before bringing PM and friends in the loop. - RS now supports fast rollback when something goes wrong while initializing the new version during a live update. - Live update is now implemented by keeping the two versions side-by-side and swapping the process slots when the old version is ready to update. - Crash recovery is now implemented by keeping the two versions side-by-side and cleaning up the old version only when the recovery process is complete. DS CHANGES: - Fixed a bug when the process doing ds_publish() or ds_delete() is not known by DS. - Fixed the completely broken support for strings. String publishing is now implemented in the system library and simply wraps publishing of memory ranges. Ideally, we should adopt a similar approach for other data types as well. - Test suite fixed. DRIVER CHANGES: - The hello driver has been added to the Minix distribution to demonstrate basic live update and crash recovery functionalities. - Other drivers have been adapted to conform the new SEF interface.
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int srv_execve(int proc_e, char *exec, size_t exec_len, char **argv,
char **UNUSED(Xenvp))
{
char * const *ap;
char * const *ep;
char *frame;
char **vp;
char *sp, *progname;
size_t argc;
size_t frame_size;
size_t string_off;
size_t n;
int ov;
int r;
/* Assumptions: size_t and char *, it's all the same thing. */
/* Create a stack image that only needs to be patched up slightly
* by the kernel to be used for the process to be executed.
*/
ov= 0; /* No overflow yet. */
frame_size= 0; /* Size of the new initial stack. */
string_off= 0; /* Offset to start of the strings. */
argc= 0; /* Argument count. */
for (ap= argv; *ap != NULL; ap++) {
n = sizeof(*ap) + strlen(*ap) + 1;
frame_size+= n;
if (frame_size < n) ov= 1;
string_off+= sizeof(*ap);
argc++;
}
/* Add an argument count and two terminating nulls. */
frame_size+= sizeof(argc) + sizeof(*ap) + sizeof(*ep);
string_off+= sizeof(argc) + sizeof(*ap) + sizeof(*ep);
/* Align. */
frame_size= (frame_size + sizeof(char *) - 1) & ~(sizeof(char *) - 1);
/* The party is off if there is an overflow. */
if (ov || frame_size < 3 * sizeof(char *)) {
errno= E2BIG;
return -1;
}
/* Allocate space for the stack frame. */
frame = (char *) malloc(frame_size);
if (!frame) {
errno = E2BIG;
return -1;
}
/* Set arg count, init pointers to vector and string tables. */
* (size_t *) frame = argc;
vp = (char **) (frame + sizeof(argc));
sp = frame + string_off;
/* Load the argument vector and strings. */
for (ap= argv; *ap != NULL; ap++) {
*vp++= (char *) (sp - frame);
n= strlen(*ap) + 1;
memcpy(sp, *ap, n);
sp+= n;
}
*vp++= NULL;
#if 0
/* Load the environment vector and strings. */
for (ep= envp; *ep != NULL; ep++) {
*vp++= (char *) (sp - frame);
n= strlen(*ep) + 1;
memcpy(sp, *ep, n);
sp+= n;
}
#endif
*vp++= NULL;
/* Padding. */
while (sp < frame + frame_size) *sp++= 0;
(progname=strrchr(argv[0], '/')) ? progname++ : (progname=argv[0]);
r = do_exec(proc_e, exec, exec_len, progname, frame, frame_size);
/* Return the memory used for the frame and exit. */
free(frame);
return r;
}
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static int do_exec(int proc_e, char *exec, size_t exec_len, char *progname,
char *frame, int frame_len)
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{
int r;
vir_bytes vsp;
struct exec_info execi;
int i;
memset(&execi, 0, sizeof(execi));
No more intel/minix segments. This commit removes all traces of Minix segments (the text/data/stack memory map abstraction in the kernel) and significance of Intel segments (hardware segments like CS, DS that add offsets to all addressing before page table translation). This ultimately simplifies the memory layout and addressing and makes the same layout possible on non-Intel architectures. There are only two types of addresses in the world now: virtual and physical; even the kernel and processes have the same virtual address space. Kernel and user processes can be distinguished at a glance as processes won't use 0xF0000000 and above. No static pre-allocated memory sizes exist any more. Changes to booting: . The pre_init.c leaves the kernel and modules exactly as they were left by the bootloader in physical memory . The kernel starts running using physical addressing, loaded at a fixed location given in its linker script by the bootloader. All code and data in this phase are linked to this fixed low location. . It makes a bootstrap pagetable to map itself to a fixed high location (also in linker script) and jumps to the high address. All code and data then use this high addressing. . All code/data symbols linked at the low addresses is prefixed by an objcopy step with __k_unpaged_*, so that that code cannot reference highly-linked symbols (which aren't valid yet) or vice versa (symbols that aren't valid any more). . The two addressing modes are separated in the linker script by collecting the unpaged_*.o objects and linking them with low addresses, and linking the rest high. Some objects are linked twice, once low and once high. . The bootstrap phase passes a lot of information (e.g. free memory list, physical location of the modules, etc.) using the kinfo struct. . After this bootstrap the low-linked part is freed. . The kernel maps in VM into the bootstrap page table so that VM can begin executing. Its first job is to make page tables for all other boot processes. So VM runs before RS, and RS gets a fully dynamic, VM-managed address space. VM gets its privilege info from RS as usual but that happens after RS starts running. . Both the kernel loading VM and VM organizing boot processes happen using the libexec logic. This removes the last reason for VM to still know much about exec() and vm/exec.c is gone. Further Implementation: . All segments are based at 0 and have a 4 GB limit. . The kernel is mapped in at the top of the virtual address space so as not to constrain the user processes. . Processes do not use segments from the LDT at all; there are no segments in the LDT any more, so no LLDT is needed. . The Minix segments T/D/S are gone and so none of the user-space or in-kernel copy functions use them. The copy functions use a process endpoint of NONE to realize it's a physical address, virtual otherwise. . The umap call only makes sense to translate a virtual address to a physical address now. . Segments-related calls like newmap and alloc_segments are gone. . All segments-related translation in VM is gone (vir2map etc). . Initialization in VM is simpler as no moving around is necessary. . VM and all other boot processes can be linked wherever they wish and will be mapped in at the right location by the kernel and VM respectively. Other changes: . The multiboot code is less special: it does not use mb_print for its diagnostics any more but uses printf() as normal, saving the output into the diagnostics buffer, only printing to the screen using the direct print functions if a panic() occurs. . The multiboot code uses the flexible 'free memory map list' style to receive the list of free memory if available. . The kernel determines the memory layout of the processes to a degree: it tells VM where the kernel starts and ends and where the kernel wants the top of the process to be. VM then uses this entire range, i.e. the stack is right at the top, and mmap()ped bits of memory are placed below that downwards, and the break grows upwards. Other Consequences: . Every process gets its own page table as address spaces can't be separated any more by segments. . As all segments are 0-based, there is no distinction between virtual and linear addresses, nor between userspace and kernel addresses. . Less work is done when context switching, leading to a net performance increase. (8% faster on my machine for 'make servers'.) . The layout and configuration of the GDT makes sysenter and syscall possible.
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execi.stack_high = kinfo.user_sp;
execi.stack_size = DEFAULT_STACK_LIMIT;
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execi.proc_e = proc_e;
execi.hdr = exec;
execi.filesize = execi.hdr_len = exec_len;
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strncpy(execi.progname, progname, PROC_NAME_LEN-1);
execi.progname[PROC_NAME_LEN-1] = '\0';
execi.frame_len = frame_len;
/* callback functions and data */
execi.copymem = read_seg;
execi.clearproc = libexec_clearproc_vm_procctl;
execi.clearmem = libexec_clear_sys_memset;
execi.allocmem_prealloc_cleared = libexec_alloc_mmap_prealloc_cleared;
execi.allocmem_prealloc_junk = libexec_alloc_mmap_prealloc_junk;
execi.allocmem_ondemand = libexec_alloc_mmap_ondemand;
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for(i = 0; exec_loaders[i].load_object != NULL; i++) {
r = (*exec_loaders[i].load_object)(&execi);
/* Loaded successfully, so no need to try other loaders */
if (r == OK) break;
}
/* No exec loader could load the object */
if (r != OK) {
printf("RS: do_exec: loading error %d\n", r);
return r;
}
/* Inform PM */
if((r = libexec_pm_newexec(execi.proc_e, &execi)) != OK)
return r;
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/* Patch up stack and copy it from RS to new core image. */
vsp = execi.stack_high;
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vsp -= frame_len;
libexec_patch_ptr(frame, vsp);
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r = sys_datacopy(SELF, (vir_bytes) frame,
proc_e, (vir_bytes) vsp, (phys_bytes)frame_len);
if (r != OK) {
printf("do_exec: copying out new stack failed: %d\n", r);
exec_restart(proc_e, r, execi.pc);
return r;
}
return exec_restart(proc_e, OK, execi.pc);
}
/*===========================================================================*
* exec_restart *
*===========================================================================*/
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static int exec_restart(int proc_e, int result, vir_bytes pc)
{
int r;
message m;
m.m_type= EXEC_RESTART;
m.EXC_RS_PROC= proc_e;
m.EXC_RS_RESULT= result;
m.EXC_RS_PC= (void*)pc;
r= sendrec(PM_PROC_NR, &m);
if (r != OK)
return r;
return m.m_type;
}
/*===========================================================================*
* read_seg *
*===========================================================================*/
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static int read_seg(
struct exec_info *execi, /* various data needed for exec */
off_t off, /* offset in file */
off_t seg_addr, /* address to load segment */
size_t seg_bytes /* how much is to be transferred? */
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)
{
/*
* The byte count on read is usually smaller than the segment count, because
* a segment is padded out to a click multiple, and the data segment is only
* partially initialized.
*/
int r;
if (off+seg_bytes > execi->hdr_len) return ENOEXEC;
if((r= sys_vircopy(SELF, ((vir_bytes)execi->hdr)+off,
execi->proc_e, seg_addr, seg_bytes)) != OK) {
printf("RS: exec read_seg: copy 0x%x bytes into %i at 0x%08x failed: %i\n",
seg_bytes, execi->proc_e, seg_addr, r);
}
return r;
}