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MIPS: uaccess: Remove get_fs/set_fs call sites
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Use new helpers to access user/kernel for functions, which are used with
user/kernel pointers. Instead of dealing with get_fs/set_fs select
user/kernel access via parameter.

Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Thomas Bogendoerfer committed Apr 6, 2021
1 parent 08ee3a0 commit 45deb5f
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Showing 3 changed files with 136 additions and 186 deletions.
18 changes: 18 additions & 0 deletions arch/mips/kernel/access-helper.h
View file
Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
/* SPDX-License-Identifier: GPL-2.0 */

#include <linux/uaccess.h>

static inline int __get_addr(unsigned long *a, unsigned long *p, bool user)
{
return user ? get_user(*a, p) : get_kernel_nofault(*a, p);
}

static inline int __get_inst16(u16 *i, u16 *p, bool user)
{
return user ? get_user(*i, p) : get_kernel_nofault(*i, p);
}

static inline int __get_inst32(u32 *i, u32 *p, bool user)
{
return user ? get_user(*i, p) : get_kernel_nofault(*i, p);
}
105 changes: 46 additions & 59 deletions arch/mips/kernel/traps.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -72,6 +72,8 @@

#include <asm/mach-loongson64/cpucfg-emul.h>

#include "access-helper.h"

extern void check_wait(void);
extern asmlinkage void rollback_handle_int(void);
extern asmlinkage void handle_int(void);
Expand Down Expand Up @@ -108,7 +110,8 @@ void (*board_bind_eic_interrupt)(int irq, int regset);
void (*board_ebase_setup)(void);
void(*board_cache_error_setup)(void);

static void show_raw_backtrace(unsigned long reg29, const char *loglvl)
static void show_raw_backtrace(unsigned long reg29, const char *loglvl,
bool user)
{
unsigned long *sp = (unsigned long *)(reg29 & ~3);
unsigned long addr;
Expand All @@ -118,9 +121,7 @@ static void show_raw_backtrace(unsigned long reg29, const char *loglvl)
printk("%s\n", loglvl);
#endif
while (!kstack_end(sp)) {
unsigned long __user *p =
(unsigned long __user *)(unsigned long)sp++;
if (__get_user(addr, p)) {
if (__get_addr(&addr, sp++, user)) {
printk("%s (Bad stack address)", loglvl);
break;
}
Expand All @@ -141,7 +142,7 @@ __setup("raw_show_trace", set_raw_show_trace);
#endif

static void show_backtrace(struct task_struct *task, const struct pt_regs *regs,
const char *loglvl)
const char *loglvl, bool user)
{
unsigned long sp = regs->regs[29];
unsigned long ra = regs->regs[31];
Expand All @@ -151,7 +152,7 @@ static void show_backtrace(struct task_struct *task, const struct pt_regs *regs,
task = current;

if (raw_show_trace || user_mode(regs) || !__kernel_text_address(pc)) {
show_raw_backtrace(sp, loglvl);
show_raw_backtrace(sp, loglvl, user);
return;
}
printk("%sCall Trace:\n", loglvl);
Expand All @@ -167,12 +168,12 @@ static void show_backtrace(struct task_struct *task, const struct pt_regs *regs,
* with at least a bit of error checking ...
*/
static void show_stacktrace(struct task_struct *task,
const struct pt_regs *regs, const char *loglvl)
const struct pt_regs *regs, const char *loglvl, bool user)
{
const int field = 2 * sizeof(unsigned long);
long stackdata;
unsigned long stackdata;
int i;
unsigned long __user *sp = (unsigned long __user *)regs->regs[29];
unsigned long *sp = (unsigned long *)regs->regs[29];

printk("%sStack :", loglvl);
i = 0;
Expand All @@ -186,7 +187,7 @@ static void show_stacktrace(struct task_struct *task,
break;
}

if (__get_user(stackdata, sp++)) {
if (__get_addr(&stackdata, sp++, user)) {
pr_cont(" (Bad stack address)");
break;
}
Expand All @@ -195,13 +196,12 @@ static void show_stacktrace(struct task_struct *task,
i++;
}
pr_cont("\n");
show_backtrace(task, regs, loglvl);
show_backtrace(task, regs, loglvl, user);
}

void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
{
struct pt_regs regs;
mm_segment_t old_fs = get_fs();

regs.cp0_status = KSU_KERNEL;
if (sp) {
Expand All @@ -217,33 +217,41 @@ void show_stack(struct task_struct *task, unsigned long *sp, const char *loglvl)
prepare_frametrace(&regs);
}
}
/*
* show_stack() deals exclusively with kernel mode, so be sure to access
* the stack in the kernel (not user) address space.
*/
set_fs(KERNEL_DS);
show_stacktrace(task, &regs, loglvl);
set_fs(old_fs);
show_stacktrace(task, &regs, loglvl, false);
}

static void show_code(unsigned int __user *pc)
static void show_code(void *pc, bool user)
{
long i;
unsigned short __user *pc16 = NULL;
unsigned short *pc16 = NULL;

printk("Code:");

if ((unsigned long)pc & 1)
pc16 = (unsigned short __user *)((unsigned long)pc & ~1);
pc16 = (u16 *)((unsigned long)pc & ~1);

for(i = -3 ; i < 6 ; i++) {
unsigned int insn;
if (pc16 ? __get_user(insn, pc16 + i) : __get_user(insn, pc + i)) {
pr_cont(" (Bad address in epc)\n");
break;
if (pc16) {
u16 insn16;

if (__get_inst16(&insn16, pc16 + i, user))
goto bad_address;

pr_cont("%c%04x%c", (i?' ':'<'), insn16, (i?' ':'>'));
} else {
u32 insn32;

if (__get_inst32(&insn32, (u32 *)pc + i, user))
goto bad_address;

pr_cont("%c%08x%c", (i?' ':'<'), insn32, (i?' ':'>'));
}
pr_cont("%c%0*x%c", (i?' ':'<'), pc16 ? 4 : 8, insn, (i?' ':'>'));
}
pr_cont("\n");
return;

bad_address:
pr_cont(" (Bad address in epc)\n\n");
}

static void __show_regs(const struct pt_regs *regs)
Expand Down Expand Up @@ -356,7 +364,6 @@ void show_regs(struct pt_regs *regs)
void show_registers(struct pt_regs *regs)
{
const int field = 2 * sizeof(unsigned long);
mm_segment_t old_fs = get_fs();

__show_regs(regs);
print_modules();
Expand All @@ -371,13 +378,9 @@ void show_registers(struct pt_regs *regs)
printk("*HwTLS: %0*lx\n", field, tls);
}

if (!user_mode(regs))
/* Necessary for getting the correct stack content */
set_fs(KERNEL_DS);
show_stacktrace(current, regs, KERN_DEFAULT);
show_code((unsigned int __user *) regs->cp0_epc);
show_stacktrace(current, regs, KERN_DEFAULT, user_mode(regs));
show_code((void *)regs->cp0_epc, user_mode(regs));
printk("\n");
set_fs(old_fs);
}

static DEFINE_RAW_SPINLOCK(die_lock);
Expand Down Expand Up @@ -1022,18 +1025,14 @@ asmlinkage void do_bp(struct pt_regs *regs)
unsigned long epc = msk_isa16_mode(exception_epc(regs));
unsigned int opcode, bcode;
enum ctx_state prev_state;
mm_segment_t seg;

seg = get_fs();
if (!user_mode(regs))
set_fs(KERNEL_DS);
bool user = user_mode(regs);

prev_state = exception_enter();
current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
if (get_isa16_mode(regs->cp0_epc)) {
u16 instr[2];

if (__get_user(instr[0], (u16 __user *)epc))
if (__get_inst16(&instr[0], (u16 *)epc, user))
goto out_sigsegv;

if (!cpu_has_mmips) {
Expand All @@ -1044,13 +1043,13 @@ asmlinkage void do_bp(struct pt_regs *regs)
bcode = instr[0] & 0xf;
} else {
/* 32-bit microMIPS BREAK */
if (__get_user(instr[1], (u16 __user *)(epc + 2)))
if (__get_inst16(&instr[1], (u16 *)(epc + 2), user))
goto out_sigsegv;
opcode = (instr[0] << 16) | instr[1];
bcode = (opcode >> 6) & ((1 << 20) - 1);
}
} else {
if (__get_user(opcode, (unsigned int __user *)epc))
if (__get_inst32(&opcode, (u32 *)epc, user))
goto out_sigsegv;
bcode = (opcode >> 6) & ((1 << 20) - 1);
}
Expand Down Expand Up @@ -1100,7 +1099,6 @@ asmlinkage void do_bp(struct pt_regs *regs)
do_trap_or_bp(regs, bcode, TRAP_BRKPT, "Break");

out:
set_fs(seg);
exception_exit(prev_state);
return;

Expand All @@ -1114,25 +1112,21 @@ asmlinkage void do_tr(struct pt_regs *regs)
u32 opcode, tcode = 0;
enum ctx_state prev_state;
u16 instr[2];
mm_segment_t seg;
bool user = user_mode(regs);
unsigned long epc = msk_isa16_mode(exception_epc(regs));

seg = get_fs();
if (!user_mode(regs))
set_fs(KERNEL_DS);

prev_state = exception_enter();
current->thread.trap_nr = (regs->cp0_cause >> 2) & 0x1f;
if (get_isa16_mode(regs->cp0_epc)) {
if (__get_user(instr[0], (u16 __user *)(epc + 0)) ||
__get_user(instr[1], (u16 __user *)(epc + 2)))
if (__get_inst16(&instr[0], (u16 *)(epc + 0), user) ||
__get_inst16(&instr[1], (u16 *)(epc + 2), user))
goto out_sigsegv;
opcode = (instr[0] << 16) | instr[1];
/* Immediate versions don't provide a code. */
if (!(opcode & OPCODE))
tcode = (opcode >> 12) & ((1 << 4) - 1);
} else {
if (__get_user(opcode, (u32 __user *)epc))
if (__get_inst32(&opcode, (u32 *)epc, user))
goto out_sigsegv;
/* Immediate versions don't provide a code. */
if (!(opcode & OPCODE))
Expand All @@ -1142,7 +1136,6 @@ asmlinkage void do_tr(struct pt_regs *regs)
do_trap_or_bp(regs, tcode, 0, "Trap");

out:
set_fs(seg);
exception_exit(prev_state);
return;

Expand Down Expand Up @@ -1591,7 +1584,6 @@ asmlinkage void do_mcheck(struct pt_regs *regs)
{
int multi_match = regs->cp0_status & ST0_TS;
enum ctx_state prev_state;
mm_segment_t old_fs = get_fs();

prev_state = exception_enter();
show_regs(regs);
Expand All @@ -1602,12 +1594,7 @@ asmlinkage void do_mcheck(struct pt_regs *regs)
dump_tlb_all();
}

if (!user_mode(regs))
set_fs(KERNEL_DS);

show_code((unsigned int __user *) regs->cp0_epc);

set_fs(old_fs);
show_code((void *)regs->cp0_epc, user_mode(regs));

/*
* Some chips may have other causes of machine check (e.g. SB1
Expand Down
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