Commit 76ed9158 authored by Benjamin Berg's avatar Benjamin Berg Committed by Johannes Berg
Browse files

um: Rework syscall handling 



Rework syscall handling to be platform independent. Also create a clean
split between queueing of syscalls and flushing them out, removing the
need to keep state in the code that triggers the syscalls.

The code adds syscall_data_len to the global mm_id structure. This will
be used later to allow surrounding code to track whether syscalls still
need to run and if errors occurred.

Signed-off-by: default avatarBenjamin Berg <benjamin@sipsolutions.net>
Link: https://patch.msgid.link/20240703134536.1161108-5-benjamin@sipsolutions.net


Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 542dc79f

arch/um/include/shared/os.h

+9 −13
Original line number Diff line number Diff line
@@ -272,19 +272,15 @@ extern long long os_persistent_clock_emulation(void); 
extern long long os_nsecs(void);



/* skas/mem.c */

extern long run_syscall_stub(struct mm_id * mm_idp,

			     int syscall, unsigned long *args, long expected,

			     void **addr, int done);

extern long syscall_stub_data(struct mm_id * mm_idp,

			      unsigned long *data, int data_count,

			      void **addr, void **stub_addr);

extern int map(struct mm_id * mm_idp, unsigned long virt,

int syscall_stub_flush(struct mm_id *mm_idp);

struct stub_syscall *syscall_stub_alloc(struct mm_id *mm_idp);



void map(struct mm_id *mm_idp, unsigned long virt,

	 unsigned long len, int prot, int phys_fd,

	       unsigned long long offset, int done, void **data);

extern int unmap(struct mm_id * mm_idp, unsigned long addr, unsigned long len,

		 int done, void **data);

extern int protect(struct mm_id * mm_idp, unsigned long addr,

		   unsigned long len, unsigned int prot, int done, void **data);

	 unsigned long long offset);

void unmap(struct mm_id *mm_idp, unsigned long addr, unsigned long len);

void protect(struct mm_id *mm_idp, unsigned long addr,

	     unsigned long len, unsigned int prot);



/* skas/process.c */

extern int is_skas_winch(int pid, int fd, void *data);

arch/um/include/shared/skas/mm_id.h

+1 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ struct mm_id { 
	} u;

	unsigned long stack;

	int kill;

	int syscall_data_len;

};



void __switch_mm(struct mm_id *mm_idp);

arch/um/include/shared/skas/stub-data.h

+33 −2
Original line number Diff line number Diff line
@@ -10,14 +10,45 @@ 


#include <linux/compiler_types.h>

#include <as-layout.h>

#include <sysdep/tls.h>



#define STUB_NEXT_SYSCALL(s) \

	((struct stub_syscall *) (((unsigned long) s) + (s)->cmd_len))



enum stub_syscall_type {

	STUB_SYSCALL_UNSET = 0,

	STUB_SYSCALL_MMAP,

	STUB_SYSCALL_MUNMAP,

	STUB_SYSCALL_MPROTECT,

	STUB_SYSCALL_LDT,

};



struct stub_syscall {

	union {

		struct {

			unsigned long addr;

			unsigned long length;

			unsigned long offset;

			int fd;

			int prot;

		} mem;

		struct {

			user_desc_t desc;

			int func;

		} ldt;

	};



	enum stub_syscall_type syscall;

};



struct stub_data {

	unsigned long offset;

	int fd;

	long parent_err, child_err;

	long err, child_err;



	int syscall_data_len;

	/* 128 leaves enough room for additional fields in the struct */

	unsigned char syscall_data[UM_KERN_PAGE_SIZE - 128] __aligned(16);

	struct stub_syscall syscall_data[(UM_KERN_PAGE_SIZE - 128) / sizeof(struct stub_syscall)] __aligned(16);



	/* Stack for our signal handlers and for calling into . */

	unsigned char sigstack[UM_KERN_PAGE_SIZE] __aligned(UM_KERN_PAGE_SIZE);

arch/um/include/shared/user.h

+8 −0
Original line number Diff line number Diff line
@@ -42,11 +42,19 @@ extern void panic(const char *fmt, ...) 
#define printk(...) _printk(__VA_ARGS__)

extern int _printk(const char *fmt, ...)

	__attribute__ ((format (printf, 1, 2)));

extern void print_hex_dump(const char *level, const char *prefix_str,

			   int prefix_type, int rowsize, int groupsize,

			   const void *buf, size_t len, _Bool ascii);

#else

static inline int printk(const char *fmt, ...)

{

	return 0;

}

static inline void print_hex_dump(const char *level, const char *prefix_str,

				  int prefix_type, int rowsize, int groupsize,

				  const void *buf, size_t len, _Bool ascii)

{

}

#endif



extern int in_aton(char *str);

arch/um/kernel/exec.c

+3 −7
Original line number Diff line number Diff line
@@ -22,15 +22,11 @@ 


void flush_thread(void)

{

	void *data = NULL;

	int ret;



	arch_flush_thread(&current->thread.arch);



	ret = unmap(&current->mm->context.id, 0, TASK_SIZE, 1, &data);

	if (ret) {

		printk(KERN_ERR "%s - clearing address space failed, err = %d\n",

		       __func__, ret);

	unmap(&current->mm->context.id, 0, TASK_SIZE);

	if (syscall_stub_flush(&current->mm->context.id) < 0) {

		printk(KERN_ERR "%s - clearing address space failed", __func__);

		force_sig(SIGKILL);

	}

	get_safe_registers(current_pt_regs()->regs.gp,