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arm64: debug: re-enable irqs before sending breakpoint SIGTRAP 

force_sig_info can sleep under an -rt kernel, so attempting to send a
breakpoint SIGTRAP with interrupts disabled yields the following BUG:

  BUG: sleeping function called from invalid context at
  /kernel-source/kernel/locking/rtmutex.c:917
  in_atomic(): 0, irqs_disabled(): 128, pid: 551, name: test.sh
  CPU: 5 PID: 551 Comm: test.sh Not tainted 4.1.13-rt13 #7
  Hardware name: Freescale Layerscape 2085a RDB Board (DT)
  Call trace:
	 dump_backtrace+0x0/0x128
	 show_stack+0x24/0x30
	 dump_stack+0x80/0xa0
	 ___might_sleep+0x128/0x1a0
	 rt_spin_lock+0x2c/0x40
	 force_sig_info+0xcc/0x210
	 brk_handler.part.2+0x6c/0x80
	 brk_handler+0xd8/0xe8
	 do_debug_exception+0x58/0xb8

This patch fixes the problem by ensuring that interrupts are enabled
prior to sending the SIGTRAP if they were already enabled in the user
context.

Reported-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Will Deacon 2016-02-10 16:05:28 +00:00
parent bcaf669b4b
commit e04a28d45f
1 changed files with 22 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
arch/arm64/kernel/debug-monitors.c
View File

@ -226,11 +226,28 @@ static int call_step_hook(struct pt_regs *regs, unsigned int esr)
return retval;
}
static void send_user_sigtrap(int si_code)
{
struct pt_regs *regs = current_pt_regs();
siginfo_t info = {
.si_signo = SIGTRAP,
.si_errno = 0,
.si_code = si_code,
.si_addr = (void __user *)instruction_pointer(regs),
};
if (WARN_ON(!user_mode(regs)))
return;
if (interrupts_enabled(regs))
local_irq_enable();
force_sig_info(SIGTRAP, &info, current);
}
static int single_step_handler(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
siginfo_t info;
/*
* If we are stepping a pending breakpoint, call the hw_breakpoint
* handler first.
@ -239,11 +256,7 @@ static int single_step_handler(unsigned long addr, unsigned int esr,
return 0;
if (user_mode(regs)) {
info.si_signo = SIGTRAP;
info.si_errno = 0;
info.si_code = TRAP_HWBKPT;
info.si_addr = (void __user *)instruction_pointer(regs);
force_sig_info(SIGTRAP, &info, current);
send_user_sigtrap(TRAP_HWBKPT);
/*
* ptrace will disable single step unless explicitly
@ -307,17 +320,8 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr)
static int brk_handler(unsigned long addr, unsigned int esr,
struct pt_regs *regs)
{
siginfo_t info;
if (user_mode(regs)) {
info = (siginfo_t) {
.si_signo = SIGTRAP,
.si_errno = 0,
.si_code = TRAP_BRKPT,
.si_addr = (void __user *)instruction_pointer(regs),
};
force_sig_info(SIGTRAP, &info, current);
send_user_sigtrap(TRAP_BRKPT);
} else if (call_break_hook(regs, esr) != DBG_HOOK_HANDLED) {
pr_warning("Unexpected kernel BRK exception at EL1\n");
return -EFAULT;
@ -328,7 +332,6 @@ static int brk_handler(unsigned long addr, unsigned int esr,
int aarch32_break_handler(struct pt_regs *regs)
{
siginfo_t info;
u32 arm_instr;
u16 thumb_instr;
bool bp = false;
@ -359,14 +362,7 @@ int aarch32_break_handler(struct pt_regs *regs)
if (!bp)
return -EFAULT;
info = (siginfo_t) {
.si_signo = SIGTRAP,
.si_errno = 0,
.si_code = TRAP_BRKPT,
.si_addr = pc,
};
force_sig_info(SIGTRAP, &info, current);
send_user_sigtrap(TRAP_BRKPT);
return 0;
}