提交 3751d3e8 编写于 作者: J Jason Wessel

x86,kgdb: Fix DEBUG_RODATA limitation using text_poke()

There has long been a limitation using software breakpoints with a
kernel compiled with CONFIG_DEBUG_RODATA going back to 2.6.26. For
this particular patch, it will apply cleanly and has been tested all
the way back to 2.6.36.

The kprobes code uses the text_poke() function which accommodates
writing a breakpoint into a read-only page.  The x86 kgdb code can
solve the problem similarly by overriding the default breakpoint
set/remove routines and using text_poke() directly.

The x86 kgdb code 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.

Cc: x86@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: stable@vger.kernel.org # >= 2.6.36
Inspried-by: NMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: NJason Wessel <jason.wessel@windriver.com>
上级 98b54aa1
......@@ -43,6 +43,8 @@
#include <linux/smp.h>
#include <linux/nmi.h>
#include <linux/hw_breakpoint.h>
#include <linux/uaccess.h>
#include <linux/memory.h>
#include <asm/debugreg.h>
#include <asm/apicdef.h>
......@@ -742,6 +744,64 @@ void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
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;
/*
* It is safe to call text_poke() because normal kernel execution
* is stopped on all cores, so long as the text_mutex is not locked.
*/
if (mutex_is_locked(&text_mutex))
return -EBUSY;
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;
/*
* It is safe to call text_poke() because normal kernel execution
* is stopped on all cores, so long as the text_mutex is not locked.
*/
if (mutex_is_locked(&text_mutex))
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 },
......
......@@ -968,22 +968,6 @@ static void run_singlestep_break_test(void)
kgdbts_break_test();
}
static void test_debug_rodata(void)
{
#ifdef CONFIG_DEBUG_RODATA
/* Until there is an api to write to read-only text segments, use
* HW breakpoints for the remainder of any tests, else print a
* failure message if hw breakpoints do not work.
*/
if (!(arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT && hwbreaks_ok)) {
eprintk("kgdbts: HW breakpoints BROKEN, ending tests\n");
return;
}
force_hwbrks = 1;
v1printk("kgdbts:Using HW breakpoints for SW breakpoint tests\n");
#endif /* CONFIG_DEBUG_RODATA */
}
static void kgdbts_run_tests(void)
{
char *ptr;
......@@ -1016,7 +1000,6 @@ static void kgdbts_run_tests(void)
v1printk("kgdbts:RUN access write breakpoint test\n");
run_hw_break_test(0);
}
test_debug_rodata();
/* required internal KGDB tests */
v1printk("kgdbts:RUN plant and detach test\n");
......
......@@ -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 {
......
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