* [PATCH] unicore32: use get_kernel_nofault in dump mem and dump_instr
@ 2020-07-20 11:43 Christoph Hellwig
2020-07-21 2:09 ` Guan Xuetao
0 siblings, 1 reply; 3+ messages in thread
From: Christoph Hellwig @ 2020-07-20 11:43 UTC (permalink / raw)
To: gxt; +Cc: linux-kernel
Use the proper get_kernel_nofault helper to access an unsafe kernel
pointer without faulting instead of playing with set_fs and get_user.
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
arch/unicore32/kernel/traps.c | 28 +++-------------------------
1 file changed, 3 insertions(+), 25 deletions(-)
diff --git a/arch/unicore32/kernel/traps.c b/arch/unicore32/kernel/traps.c
index a3ac01df1a2e43..c1964a4a1edbb0 100644
--- a/arch/unicore32/kernel/traps.c
+++ b/arch/unicore32/kernel/traps.c
@@ -65,17 +65,8 @@ 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(KERN_DEFAULT "%s%s(0x%08lx to 0x%08lx)\n",
lvl, str, bottom, top);
@@ -89,7 +80,8 @@ 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)
+ == 0)
sprintf(str + i * 9, " %08lx", val);
else
sprintf(str + i * 9, " ????????");
@@ -97,31 +89,19 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
}
printk(KERN_DEFAULT "%s%04lx:%s\n", lvl, first & 0xffff, str);
}
-
- set_fs(fs);
}
static void dump_instr(const char *lvl, struct pt_regs *regs)
{
unsigned long addr = instruction_pointer(regs);
const int width = 8;
- mm_segment_t fs;
char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
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);
-
for (i = -4; i < 1; i++) {
unsigned int val, bad;
- bad = __get_user(val, &((u32 *)addr)[i]);
-
+ bad = get_kernel_nofault(val, &((u32 *)addr)[i]);
if (!bad)
p += sprintf(p, i == 0 ? "(%0*x) " : "%0*x ",
width, val);
@@ -131,8 +111,6 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
}
}
printk(KERN_DEFAULT "%sCode: %s\n", lvl, str);
-
- set_fs(fs);
}
static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
--
2.27.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] unicore32: use get_kernel_nofault in dump mem and dump_instr
2020-07-20 11:43 [PATCH] unicore32: use get_kernel_nofault in dump mem and dump_instr Christoph Hellwig
@ 2020-07-21 2:09 ` Guan Xuetao
2020-07-21 4:59 ` christoph hellwig
0 siblings, 1 reply; 3+ messages in thread
From: Guan Xuetao @ 2020-07-21 2:09 UTC (permalink / raw)
To: christoph hellwig; +Cc: linux-kernel
Very good to remove ds/fs in unicore arch.
Could u send me full patch for test?
Guan Xuetao
> -----原始邮件-----
> 发件人: "Christoph Hellwig" <hch@lst.de>
> 发送时间: 2020-07-20 19:43:58 (星期一)
> 收件人: gxt@pku.edu.cn
> 抄送: linux-kernel@vger.kernel.org
> 主题: [PATCH] unicore32: use get_kernel_nofault in dump mem and dump_instr
>
> Use the proper get_kernel_nofault helper to access an unsafe kernel
> pointer without faulting instead of playing with set_fs and get_user.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> arch/unicore32/kernel/traps.c | 28 +++-------------------------
> 1 file changed, 3 insertions(+), 25 deletions(-)
>
> diff --git a/arch/unicore32/kernel/traps.c b/arch/unicore32/kernel/traps.c
> index a3ac01df1a2e43..c1964a4a1edbb0 100644
> --- a/arch/unicore32/kernel/traps.c
> +++ b/arch/unicore32/kernel/traps.c
> @@ -65,17 +65,8 @@ 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(KERN_DEFAULT "%s%s(0x%08lx to 0x%08lx)\n",
> lvl, str, bottom, top);
>
> @@ -89,7 +80,8 @@ 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)
> + == 0)
> sprintf(str + i * 9, " %08lx", val);
> else
> sprintf(str + i * 9, " ????????");
> @@ -97,31 +89,19 @@ static void dump_mem(const char *lvl, const char *str, unsigned long bottom,
> }
> printk(KERN_DEFAULT "%s%04lx:%s\n", lvl, first & 0xffff, str);
> }
> -
> - set_fs(fs);
> }
>
> static void dump_instr(const char *lvl, struct pt_regs *regs)
> {
> unsigned long addr = instruction_pointer(regs);
> const int width = 8;
> - mm_segment_t fs;
> char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
> 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);
> -
> for (i = -4; i < 1; i++) {
> unsigned int val, bad;
>
> - bad = __get_user(val, &((u32 *)addr)[i]);
> -
> + bad = get_kernel_nofault(val, &((u32 *)addr)[i]);
> if (!bad)
> p += sprintf(p, i == 0 ? "(%0*x) " : "%0*x ",
> width, val);
> @@ -131,8 +111,6 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
> }
> }
> printk(KERN_DEFAULT "%sCode: %s\n", lvl, str);
> -
> - set_fs(fs);
> }
>
> static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
> --
> 2.27.0
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] unicore32: use get_kernel_nofault in dump mem and dump_instr
2020-07-21 2:09 ` Guan Xuetao
@ 2020-07-21 4:59 ` christoph hellwig
0 siblings, 0 replies; 3+ messages in thread
From: christoph hellwig @ 2020-07-21 4:59 UTC (permalink / raw)
To: Guan Xuetao; +Cc: christoph hellwig, linux-kernel
On Tue, Jul 21, 2020 at 10:09:20AM +0800, Guan Xuetao wrote:
> Very good to remove ds/fs in unicore arch.
> Could u send me full patch for test?
This is the full patch for now. The actual removal will need
more core instrastructure and at least one more merge window.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-07-20 11:43 [PATCH] unicore32: use get_kernel_nofault in dump mem and dump_instr Christoph Hellwig
2020-07-21 2:09 ` Guan Xuetao
2020-07-21 4:59 ` christoph hellwig
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