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Subject[tip: x86/core] x86/traps: Cleanup do_general_protection()
The following commit has been merged into the x86/core branch of tip:

Commit-ID: 36209766cede1fe9d39f3d3418d93bbf71ad21c4
Gitweb: https://git.kernel.org/tip/36209766cede1fe9d39f3d3418d93bbf71ad21c4
Author: Borislav Petkov <bp@suse.de>
AuthorDate: Tue, 31 Dec 2019 17:15:35 +01:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Tue, 31 Dec 2019 17:29:29 +01:00

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
---
arch/x86/kernel/traps.c | 79 ++++++++++++++++++++--------------------
1 file changed, 40 insertions(+), 39 deletions(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 2afd7d8..ca395ad 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -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;
+ return;
+ }

- if (error_code)
- snprintf(desc, sizeof(desc), "segment-related " GPFSTR);
- else
- hint = get_kernel_gp_address(regs, &gp_addr);
+ if (fixup_exception(regs, X86_TRAP_GP, error_code, 0))
+ return;

- 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);
+ tsk->thread.error_code = error_code;
+ tsk->thread.trap_nr = X86_TRAP_GP;

- /*
- * KASAN is interested only in the non-canonical case, clear it
- * otherwise.
- */
- if (hint != GP_NON_CANONICAL)
- gp_addr = 0;
+ /*
+ * 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;

- die_addr(desc, regs, error_code, gp_addr);
+ ret = notify_die(DIE_GPF, desc, regs, error_code, X86_TRAP_GP, SIGSEGV);
+ if (ret == NOTIFY_STOP)
return;
- }

- tsk->thread.error_code = error_code;
- tsk->thread.trap_nr = X86_TRAP_GP;
+ 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;

- show_signal(tsk, SIGSEGV, "", desc, regs, error_code);
+ die_addr(desc, regs, error_code, gp_addr);

- force_sig(SIGSEGV);
}
NOKPROBE_SYMBOL(do_general_protection);

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