[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <4F6C8AD9.40201@windriver.com>
Date: Fri, 23 Mar 2012 09:38:17 -0500
From: Jason Wessel <jason.wessel@...driver.com>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
CC: <linux-kernel@...r.kernel.org>,
<kgdb-bugreport@...ts.sourceforge.net>, <tim.bird@...sony.com>
Subject: Re: [PATCH 2/2] kgdb,debug_core,kgdbts: End DEBUG_RODATA limitation
using kprobe breakpoints
On 03/23/2012 09:08 AM, Masami Hiramatsu wrote:
> (2012/03/22 20:57), Jason Wessel wrote:
>> I will use the arch specific provision to override the
>> kgdb_arch_set_breakpoint() and use the text_poke() directly.
>
> Thanks! that's what I meant. You can use __weak attribute.
>
I created and tested a patch yesterday which is show below. I will
post a new series at some point soon which addresses this problem as
well as a number of problems found with the kgdb test suite.
Cheers,
Jason.
Subject: [PATCH] x86,kgdb: End DEBUG_RODATA limitation using text_poke()
There has long been a limitation using software breakpoints with a
kernel compiled with CONFIG_DEBUG_RODATA. The kprobes code has long
used the text_poke() function which accommodates writing a breakpoint
into a read-only page. The x86 arch can override the default
breakpoint install remove routines and make use of the text_poke()
code that comes from the x86 alternatives.
The x86 arch will first attempt to use the traditional
probe_kernel_write(), and next try using a the text_poke() function.
The break point install method is tracked such that the correct break
point removal routine will get called later on.
Signed-off-by: Jason Wessel <jason.wessel@...driver.com>
---
arch/x86/kernel/kgdb.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/kgdb.h | 3 ++-
2 files changed, 48 insertions(+), 1 deletion(-)
--- a/include/linux/kgdb.h
+++ b/include/linux/kgdb.h
@@ -63,7 +63,8 @@ enum kgdb_bptype {
BP_HARDWARE_BREAKPOINT,
BP_WRITE_WATCHPOINT,
BP_READ_WATCHPOINT,
- BP_ACCESS_WATCHPOINT
+ BP_ACCESS_WATCHPOINT,
+ BP_POKE_BREAKPOINT,
};
enum kgdb_bpstate {
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -742,6 +742,52 @@ void kgdb_arch_set_pc(struct pt_regs *re
regs->ip = ip;
}
+int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
+{
+ int err;
+ char opc[BREAK_INSTR_SIZE];
+
+ bpt->type = BP_BREAKPOINT;
+ err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
+ BREAK_INSTR_SIZE);
+ if (err)
+ return err;
+ err = probe_kernel_write((char *)bpt->bpt_addr,
+ arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE);
+#ifdef CONFIG_DEBUG_RODATA
+ if (!err)
+ return err;
+ text_poke((void *)bpt->bpt_addr, arch_kgdb_ops.gdb_bpt_instr,
+ BREAK_INSTR_SIZE);
+ err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
+ if (err)
+ return err;
+ if (memcmp(opc, arch_kgdb_ops.gdb_bpt_instr, BREAK_INSTR_SIZE))
+ return -EINVAL;
+ bpt->type = BP_POKE_BREAKPOINT;
+#endif /* CONFIG_DEBUG_RODATA */
+ return err;
+}
+
+int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
+{
+#ifdef CONFIG_DEBUG_RODATA
+ int err;
+ char opc[BREAK_INSTR_SIZE];
+
+ if (bpt->type != BP_POKE_BREAKPOINT)
+ goto knl_write;
+ text_poke((void *)bpt->bpt_addr, bpt->saved_instr, BREAK_INSTR_SIZE);
+ err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
+ if (err || memcmp(opc, bpt->saved_instr, BREAK_INSTR_SIZE))
+ goto knl_write;
+ return err;
+knl_write:
+#endif /* CONFIG_DEBUG_RODATA */
+ return probe_kernel_write((char *)bpt->bpt_addr,
+ (char *)bpt->saved_instr, BREAK_INSTR_SIZE);
+}
+
struct kgdb_arch arch_kgdb_ops = {
/* Breakpoint instruction: */
.gdb_bpt_instr = { 0xcc },
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists