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SubjectRe: [PATCH 5/9] x86/dumpstack: Improve opcodes dumping in the Code: section
On Wed, Mar 07, 2018 at 01:08:32PM -0800, Linus Torvalds wrote:
> On Wed, Mar 7, 2018 at 5:25 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> >
> > How about we just remove the 'code_bytes=' option? (Or at the very
> > least, reduce its possible range to a reasonable max?)
>
> Ack. Just limit it to 64 bytes max sounds plenty.

Done, combined diff ontop. With a 64-byte on-stack opcodes buffer:

---
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index b37c1c30c16f..2c74c1694d9d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -587,11 +587,6 @@
Sets the size of memory pool for coherent, atomic dma
allocations, by default set to 256K.

- code_bytes [X86] How many bytes of object code to print
- in an oops report.
- Range: 0 - 8192
- Default: 64
-
com20020= [HW,NET] ARCnet - COM20020 chipset
Format:
<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 409a5bd02a18..2fc009a1824e 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -22,13 +22,9 @@
#include <asm/stacktrace.h>
#include <asm/unwind.h>

-#define OPCODE_BUFSIZE 64
-
int panic_on_unrecovered_nmi;
int panic_on_io_nmi;
-static unsigned int code_bytes = OPCODE_BUFSIZE;
-static u8 __opc[OPCODE_BUFSIZE];
-static u8 *opcodes = __opc;
+
static int die_counter;

static struct pt_regs exec_summary_regs;
@@ -77,19 +73,21 @@ static void printk_stack_address(unsigned long address, int reliable,

void show_opcodes(u8 *rip, const char *loglvl)
{
- unsigned int code_prologue = code_bytes * 43 / OPCODE_BUFSIZE;
+#define OPCODE_BUFSIZE 64
+ unsigned int code_prologue = OPCODE_BUFSIZE * 43 / OPCODE_BUFSIZE;
+ u8 opcodes[OPCODE_BUFSIZE];
u8 *ip;
int i;

printk("%sCode: ", loglvl);

ip = (u8 *)rip - code_prologue;
- if (probe_kernel_read(opcodes, ip, code_bytes)) {
+ if (probe_kernel_read(opcodes, ip, OPCODE_BUFSIZE)) {
pr_cont(" Bad RIP value.\n");
return;
}

- for (i = 0; i < code_bytes; i++, ip++) {
+ for (i = 0; i < OPCODE_BUFSIZE; i++, ip++) {
if (ip == (u8 *)rip)
pr_cont("<%02x> ", opcodes[i]);
else
@@ -387,34 +385,6 @@ void die(const char *str, struct pt_regs *regs, long err)
oops_end(flags, regs, sig);
}

-static int __init code_bytes_setup(char *s)
-{
- unsigned long val;
- ssize_t ret;
-
- if (!s)
- return -EINVAL;
-
- ret = kstrtoul(s, 0, &val);
- if (ret)
- return ret;
-
- code_bytes = val;
- if (code_bytes > 8192)
- code_bytes = 8192;
-
- if (code_bytes > OPCODE_BUFSIZE) {
- u8 *new_buf = kzalloc(code_bytes, GFP_KERNEL);
- if (!new_buf)
- return -ENOMEM;
-
- opcodes = new_buf;
- }
-
- return 1;
-}
-__setup("code_bytes=", code_bytes_setup);
-
void show_regs(struct pt_regs *regs)
{
bool all = true;
--
Regards/Gruss,
Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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