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x86/traps: Cleanup do_general_protection() 

Hoist the user_mode() case up because it is less code and can be dealt
with up-front like the other special cases UMIP and vm86.

This saves an indentation level for the kernel-mode #GP case and allows
to "unfold" the code more so that it is more readable.

No functional changes.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Jann Horn <jannh@google.com>
Cc: x86@kernel.org
This commit is contained in:
Borislav Petkov 2019-12-31 17:15:35 +01:00
parent 2f004eea0f
commit 36209766ce
1 changed files with 41 additions and 40 deletions
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81
arch/x86/kernel/traps.c
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@ -567,7 +567,10 @@ static enum kernel_gp_hint get_kernel_gp_address(struct pt_regs *regs,
dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code)
{
char desc[sizeof(GPFSTR) + 50 + 2*sizeof(unsigned long) + 1] = GPFSTR;
enum kernel_gp_hint hint = GP_NO_HINT;
struct task_struct *tsk;
unsigned long gp_addr;
int ret;
RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
cond_local_irq_enable(regs);
@ -584,58 +587,56 @@ dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code)
}
tsk = current;
if (!user_mode(regs)) {
enum kernel_gp_hint hint = GP_NO_HINT;
unsigned long gp_addr;
if (fixup_exception(regs, X86_TRAP_GP, error_code, 0))
return;
if (user_mode(regs)) {
tsk->thread.error_code = error_code;
tsk->thread.trap_nr = X86_TRAP_GP;
/*
* To be potentially processing a kprobe fault and to
* trust the result from kprobe_running(), we have to
* be non-preemptible.
*/
if (!preemptible() && kprobe_running() &&
kprobe_fault_handler(regs, X86_TRAP_GP))
return;
show_signal(tsk, SIGSEGV, "", desc, regs, error_code);
force_sig(SIGSEGV);
if (notify_die(DIE_GPF, desc, regs, error_code,
X86_TRAP_GP, SIGSEGV) == NOTIFY_STOP)
return;
if (error_code)
snprintf(desc, sizeof(desc), "segment-related " GPFSTR);
else
hint = get_kernel_gp_address(regs, &gp_addr);
if (hint != GP_NO_HINT)
snprintf(desc, sizeof(desc), GPFSTR ", %s 0x%lx",
(hint == GP_NON_CANONICAL) ?
"probably for non-canonical address" :
"maybe for address",
gp_addr);
/*
* KASAN is interested only in the non-canonical case, clear it
* otherwise.
*/
if (hint != GP_NON_CANONICAL)
gp_addr = 0;
die_addr(desc, regs, error_code, gp_addr);
return;
}
if (fixup_exception(regs, X86_TRAP_GP, error_code, 0))
return;
tsk->thread.error_code = error_code;
tsk->thread.trap_nr = X86_TRAP_GP;
show_signal(tsk, SIGSEGV, "", desc, regs, error_code);
/*
* To be potentially processing a kprobe fault and to trust the result
* from kprobe_running(), we have to be non-preemptible.
*/
if (!preemptible() &&
kprobe_running() &&
kprobe_fault_handler(regs, X86_TRAP_GP))
return;
ret = notify_die(DIE_GPF, desc, regs, error_code, X86_TRAP_GP, SIGSEGV);
if (ret == NOTIFY_STOP)
return;
if (error_code)
snprintf(desc, sizeof(desc), "segment-related " GPFSTR);
else
hint = get_kernel_gp_address(regs, &gp_addr);
if (hint != GP_NO_HINT)
snprintf(desc, sizeof(desc), GPFSTR ", %s 0x%lx",
(hint == GP_NON_CANONICAL) ? "probably for non-canonical address"
: "maybe for address",
gp_addr);
/*
* KASAN is interested only in the non-canonical case, clear it
* otherwise.
*/
if (hint != GP_NON_CANONICAL)
gp_addr = 0;
die_addr(desc, regs, error_code, gp_addr);
force_sig(SIGSEGV);
}
NOKPROBE_SYMBOL(do_general_protection);