* [RESEND PATCH tip] x86/idt: Remove X86_TRAP_BP initialization in idt_setup_traps()
@ 2017-11-08 19:28 Yonghong Song
2017-11-08 20:10 ` [tip:x86/urgent] " tip-bot for Yonghong Song
0 siblings, 1 reply; 2+ messages in thread
From: Yonghong Song @ 2017-11-08 19:28 UTC (permalink / raw
To: mingo, tglx, oleg, luto, hpa, a.p.zijlstra, linux-kernel, x86,
ast
Cc: kernel-team
Commit b70543a0b2b6("x86/idt: Move regular trap init to tables")
moves regular trap init for each trap vector into a table based
initialization. It introduced the initialization for vector
X86_TRAP_BP which was not in the original change and it breaks
uprobe functionality for x86_32. A program with uprobe
instrumented can have segfault on x86_32 instead of normal finish.
Uprobe still works on x86_64 even with this commit.
This patch removes X86_TRAP_BP from the structure def_idts
which is used in idt_setup_traps(). It also removes a redundant
entry for X86_TRAP_NMI in def_idts. Tested on both x86_64 and x86_32,
uprobe works fine.
Fixes: b70543a0b2b6("x86/idt: Move regular trap init to tables")
Reported-and-tested-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
arch/x86/kernel/idt.c | 2 --
1 file changed, 2 deletions(-)
[RESEND with adding linux-kernel@vger.kernel.org as the recipient.]
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index 723fa97..d985cef 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -92,8 +92,6 @@ static const __initdata struct idt_data def_idts[] = {
INTG(X86_TRAP_DF, double_fault),
#endif
INTG(X86_TRAP_DB, debug),
- INTG(X86_TRAP_NMI, nmi),
- INTG(X86_TRAP_BP, int3),
#ifdef CONFIG_X86_MCE
INTG(X86_TRAP_MC, &machine_check),
--
2.9.5
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [tip:x86/urgent] x86/idt: Remove X86_TRAP_BP initialization in idt_setup_traps()
2017-11-08 19:28 [RESEND PATCH tip] x86/idt: Remove X86_TRAP_BP initialization in idt_setup_traps() Yonghong Song
@ 2017-11-08 20:10 ` tip-bot for Yonghong Song
0 siblings, 0 replies; 2+ messages in thread
From: tip-bot for Yonghong Song @ 2017-11-08 20:10 UTC (permalink / raw
To: linux-tip-commits; +Cc: hpa, linux-kernel, yhs, mingo, tglx
Commit-ID: d0cd64b02aa854d68ce517cb7da1fe4e4fff2653
Gitweb: https://git.kernel.org/tip/d0cd64b02aa854d68ce517cb7da1fe4e4fff2653
Author: Yonghong Song <yhs@fb.com>
AuthorDate: Wed, 8 Nov 2017 11:28:45 -0800
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 8 Nov 2017 21:05:23 +0100
x86/idt: Remove X86_TRAP_BP initialization in idt_setup_traps()
Commit b70543a0b2b6("x86/idt: Move regular trap init to tables") moves
regular trap init for each trap vector into a table based
initialization. It introduced the initialization for vector X86_TRAP_BP
which was not in the code which it replaced. This breaks uprobe
functionality for x86_32; the probed program segfaults instead of handling
the probe proper.
The reason for this is that TRAP_BP is set up as system interrupt gate
(DPL3) in the early IDT and then replaced by a regular interrupt gate
(DPL0) in idt_setup_traps(). The DPL0 restriction causes the int3 trap
to fail with a #GP resulting in a SIGSEGV of the probed program.
On 64bit this does not cause a problem because the IDT entry is replaced
with a system interrupt gate (DPL3) with interrupt stack afterwards.
Remove X86_TRAP_BP from the def_idts table which is used in
idt_setup_traps(). Remove a redundant entry for X86_TRAP_NMI in def_idts
while at it. Tested on both x86_64 and x86_32.
[ tglx: Amended changelog with a description of the root cause ]
Fixes: b70543a0b2b6("x86/idt: Move regular trap init to tables")
Reported-and-tested-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: a.p.zijlstra@chello.nl
Cc: ast@fb.com
Cc: oleg@redhat.com
Cc: luto@kernel.org
Cc: kernel-team@fb.com
Link: https://lkml.kernel.org/r/20171108192845.552709-1-yhs@fb.com
---
arch/x86/kernel/idt.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index 6107ee1..014cb2f 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -92,8 +92,6 @@ static const __initdata struct idt_data def_idts[] = {
INTG(X86_TRAP_DF, double_fault),
#endif
INTG(X86_TRAP_DB, debug),
- INTG(X86_TRAP_NMI, nmi),
- INTG(X86_TRAP_BP, int3),
#ifdef CONFIG_X86_MCE
INTG(X86_TRAP_MC, &machine_check),
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2017-11-08 19:28 [RESEND PATCH tip] x86/idt: Remove X86_TRAP_BP initialization in idt_setup_traps() Yonghong Song
2017-11-08 20:10 ` [tip:x86/urgent] " tip-bot for Yonghong Song
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