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x86/entry: Convert INT3 exception to IDTENTRY_RAW

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Convert #BP to IDTENTRY_RAW:
  - Implement the C entry point with DEFINE_IDTENTRY_RAW
  - Invoke idtentry_enter/exit() from the function body
  - Emit the ASM stub with DECLARE_IDTENTRY_RAW
  - Remove the ASM idtentry in 64bit
  - Remove the open coded ASM entry code in 32bit
  - Fixup the XEN/PV code
  - Remove the old prototypes

No functional change.

This could be a plain IDTENTRY, but as Peter pointed out INT3 is broken
vs. the static key in the context tracking code as this static key might be
in the state of being patched and has an int3 which would recurse forever.
IDTENTRY_RAW is therefore chosen to allow addressing this issue without
lots of code churn.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135313.938474960@linutronix.de
This commit is contained in:
Thomas Gleixner
2020-02-25 23:16:16 +01:00
parent 0dc6cdc21b
commit 8edd7e37ae
8 changed files with 23 additions and 26 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/kernel/idt.c
View File

@@ -60,7 +60,7 @@ static bool idt_setup_done __initdata;
*/
static const __initconst struct idt_data early_idts[] = {
INTG(X86_TRAP_DB, debug),
SYSG(X86_TRAP_BP, int3),
SYSG(X86_TRAP_BP, asm_exc_int3),
#ifdef CONFIG_X86_32
INTG(X86_TRAP_PF, page_fault),
#endif

28
arch/x86/kernel/traps.c
View File

@@ -568,7 +568,7 @@ exit:
cond_local_irq_disable(regs);
}
dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
DEFINE_IDTENTRY_RAW(exc_int3)
{
/*
* poke_int3_handler() is completely self contained code; it does (and
@@ -579,16 +579,20 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
return;
/*
* Unlike any other non-IST entry, we can be called from pretty much
* any location in the kernel through kprobes -- text_poke() will most
* likely be handled by poke_int3_handler() above. This means this
* handler is effectively NMI-like.
* idtentry_enter() uses static_branch_{,un}likely() and therefore
* can trigger INT3, hence poke_int3_handler() must be done
* before. If the entry came from kernel mode, then use nmi_enter()
* because the INT3 could have been hit in any context including
* NMI.
*/
if (!user_mode(regs))
if (user_mode(regs))
idtentry_enter(regs);
else
nmi_enter();
instrumentation_begin();
#ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
if (kgdb_ll_trap(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
if (kgdb_ll_trap(DIE_INT3, "int3", regs, 0, X86_TRAP_BP,
SIGTRAP) == NOTIFY_STOP)
goto exit;
#endif /* CONFIG_KGDB_LOW_LEVEL_TRAP */
@@ -598,19 +602,21 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
goto exit;
#endif
if (notify_die(DIE_INT3, "int3", regs, error_code, X86_TRAP_BP,
if (notify_die(DIE_INT3, "int3", regs, 0, X86_TRAP_BP,
SIGTRAP) == NOTIFY_STOP)
goto exit;
cond_local_irq_enable(regs);
do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, 0, NULL);
do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, 0, 0, NULL);
cond_local_irq_disable(regs);
exit:
if (!user_mode(regs))
instrumentation_end();
if (user_mode(regs))
idtentry_exit(regs);
else
nmi_exit();
}
NOKPROBE_SYMBOL(do_int3);
#ifdef CONFIG_X86_64
/*