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ARM: 9106/1: traps: use get_kernel_nofault instead of set_fs()

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ARM uses set_fs() and __get_user() to allow the stack dumping code to
access possibly invalid pointers carefully. These can be changed to the
simpler get_kernel_nofault(), and allow the eventual removal of set_fs().

dump_instr() will print either kernel or user space pointers,
depending on how it was called. For dump_mem(), I assume we are only
interested in kernel pointers, and the only time that this is called
with user_mode(regs)==true is when the regs themselves are unreliable
as a result of the condition that caused the trap.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Arnd Bergmann 2021-08-11 08:30:19 +01:00 committed by Russell King (Oracle)
parent 2423de2e6f
commit 344179fc7e
1 changed files with 16 additions and 31 deletions
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47
arch/arm/kernel/traps.c
View file

@ -122,17 +122,8 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
unsigned long top)
{
unsigned long first;
mm_segment_t fs;
int i;
/*
* We need to switch to kernel mode so that we can use __get_user
* to safely read from kernel space. Note that we now dump the
* code first, just in case the backtrace kills us.
*/
fs = get_fs();
set_fs(KERNEL_DS);
printk("%s%s(0x%08lx to 0x%08lx)\n", lvl, str, bottom, top);
for (first = bottom & ~31; first < top; first += 32) {
@ -145,7 +136,7 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
for (p = first, i = 0; i < 8 && p < top; i++, p += 4) {
if (p >= bottom && p < top) {
unsigned long val;
if (__get_user(val, (unsigned long *)p) == 0)
if (get_kernel_nofault(val, (unsigned long *)p))
sprintf(str + i * 9, " %08lx", val);
else
sprintf(str + i * 9, " ????????");
@ -153,11 +144,9 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
}
printk("%s%04lx:%s\n", lvl, first & 0xffff, str);
}
set_fs(fs);
}
static void __dump_instr(const char *lvl, struct pt_regs *regs)
static void dump_instr(const char *lvl, struct pt_regs *regs)
{
unsigned long addr = instruction_pointer(regs);
const int thumb = thumb_mode(regs);
@ -173,10 +162,20 @@ static void __dump_instr(const char *lvl, struct pt_regs *regs)
for (i = -4; i < 1 + !!thumb; i++) {
unsigned int val, bad;
if (thumb)
bad = get_user(val, &((u16 *)addr)[i]);
else
bad = get_user(val, &((u32 *)addr)[i]);
if (!user_mode(regs)) {
if (thumb) {
u16 val16;
bad = get_kernel_nofault(val16, &((u16 *)addr)[i]);
val = val16;
} else {
bad = get_kernel_nofault(val, &((u32 *)addr)[i]);
}
} else {
if (thumb)
bad = get_user(val, &((u16 *)addr)[i]);
else
bad = get_user(val, &((u32 *)addr)[i]);
}
if (!bad)
p += sprintf(p, i == 0 ? "(%0*x) " : "%0*x ",
@ -189,20 +188,6 @@ static void __dump_instr(const char *lvl, struct pt_regs *regs)
printk("%sCode: %s\n", lvl, str);
}
static void dump_instr(const char *lvl, struct pt_regs *regs)
{
mm_segment_t fs;
if (!user_mode(regs)) {
fs = get_fs();
set_fs(KERNEL_DS);
__dump_instr(lvl, regs);
set_fs(fs);
} else {
__dump_instr(lvl, regs);
}
}
#ifdef CONFIG_ARM_UNWIND
static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
const char *loglvl)