[RFC PATCH 3/4] x86/traps: Attempt to fixup exceptions in vDSO before signaling
From: Sean Christopherson
Date: Wed Dec 05 2018 - 18:20:33 EST
Call fixup_vdso_exception() to attempt to fixup exceptions in vDSO code
before generating a signal for userspace faults. This allows vDSO
functions to utilize exception fixup to report unhandled exceptions
directly to userspace for specific flows in lieu of generating a signal.
Suggested-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kernel/traps.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9b7c4ca8f0a7..106a6cc20ad6 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -61,6 +61,7 @@
#include <asm/mpx.h>
#include <asm/vm86.h>
#include <asm/umip.h>
+#include <asm/vdso.h>
#ifdef CONFIG_X86_64
#include <asm/x86_init.h>
@@ -223,6 +224,10 @@ do_trap_no_signal(struct task_struct *tsk, int trapnr, const char *str,
tsk->thread.error_code = error_code;
tsk->thread.trap_nr = trapnr;
+ if (user_mode(regs) &&
+ fixup_vdso_exception(regs, trapnr, error_code, 0))
+ return 0;
+
return -1;
}
@@ -563,6 +568,9 @@ do_general_protection(struct pt_regs *regs, long error_code)
tsk->thread.error_code = error_code;
tsk->thread.trap_nr = X86_TRAP_GP;
+ if (fixup_vdso_exception(regs, X86_TRAP_GP, error_code, 0))
+ return;
+
show_signal(tsk, SIGSEGV, "", desc, regs, error_code);
force_sig(SIGSEGV, tsk);
@@ -854,6 +862,9 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
if (!si_code)
return;
+ if (fixup_vdso_exception(regs, trapnr, error_code, 0))
+ return;
+
force_sig_fault(SIGFPE, si_code,
(void __user *)uprobe_get_trap_addr(regs), task);
}
--
2.19.2