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| author |   Masami Hiramatsu <mhiramat@kernel.org> | 2019-08-01 23:25:49 +0900 |
|---|---|---|
| committer |   Will Deacon <will@kernel.org> | 2019-08-02 11:55:50 +0100 |
| commit | b3980e48528c4d2a9e70b145a5bba328b73a0f93 (patch) | |
| tree | c3a7b606de4fa2f00e48c1a3c36606287523c0ea /arch/arm64/include/asm/daifflags.h | |
| parent | arm64/mm: fix variable 'tag' set but not used (diff) | |
| download | linux-dev-b3980e48528c4d2a9e70b145a5bba328b73a0f93.tar.xz linux-dev-b3980e48528c4d2a9e70b145a5bba328b73a0f93.zip | |
arm64: kprobes: Recover pstate.D in single-step exception handler
kprobes manipulates the interrupted PSTATE for single step, and
doesn't restore it. Thus, if we put a kprobe where the pstate.D
(debug) masked, the mask will be cleared after the kprobe hits.
Moreover, in the most complicated case, this can lead a kernel
crash with below message when a nested kprobe hits.
[ 152.118921] Unexpected kernel single-step exception at EL1
When the 1st kprobe hits, do_debug_exception() will be called.
At this point, debug exception (= pstate.D) must be masked (=1).
But if another kprobes hits before single-step of the first kprobe
(e.g. inside user pre_handler), it unmask the debug exception
(pstate.D = 0) and return.
Then, when the 1st kprobe setting up single-step, it saves current
DAIF, mask DAIF, enable single-step, and restore DAIF.
However, since "D" flag in DAIF is cleared by the 2nd kprobe, the
single-step exception happens soon after restoring DAIF.
This has been introduced by commit 7419333fa15e ("arm64: kprobe:
Always clear pstate.D in breakpoint exception handler")
To solve this issue, this stores all DAIF bits and restore it
after single stepping.
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Fixes: 7419333fa15e ("arm64: kprobe: Always clear pstate.D in breakpoint exception handler")
Reviewed-by: James Morse <james.morse@arm.com>
Tested-by: James Morse <james.morse@arm.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
Diffstat (limited to 'arch/arm64/include/asm/daifflags.h')
| -rw-r--r-- | arch/arm64/include/asm/daifflags.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/daifflags.h b/arch/arm64/include/asm/daifflags.h index 987926ed535e..063c964af705 100644 --- a/arch/arm64/include/asm/daifflags.h +++ b/arch/arm64/include/asm/daifflags.h @@ -13,6 +13,8 @@ #define DAIF_PROCCTX 0 #define DAIF_PROCCTX_NOIRQ PSR_I_BIT #define DAIF_ERRCTX (PSR_I_BIT | PSR_A_BIT) +#define DAIF_MASK (PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT) + /* mask/save/unmask/restore all exceptions, including interrupts. */ static inline void local_daif_mask(void) |