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Re: [Qemu-arm] [PATCH 08/11] tcg/aarch64: Make direct jump patching thre
From: |
Alex Bennée |
Subject: |
Re: [Qemu-arm] [PATCH 08/11] tcg/aarch64: Make direct jump patching thread-safe |
Date: |
Wed, 20 Apr 2016 15:01:00 +0100 |
User-agent: |
mu4e 0.9.17; emacs 25.0.92.6 |
Sergey Fedorov <address@hidden> writes:
> From: Sergey Fedorov <address@hidden>
>
> Ensure direct jump patching in AArch64 is atomic by using
> atomic_read()/atomic_set() for code patching.
>
> Signed-off-by: Sergey Fedorov <address@hidden>
> Signed-off-by: Sergey Fedorov <address@hidden>
> ---
> tcg/aarch64/tcg-target.inc.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/tcg/aarch64/tcg-target.inc.c b/tcg/aarch64/tcg-target.inc.c
> index 0ed10a974121..15fdebec921f 100644
> --- a/tcg/aarch64/tcg-target.inc.c
> +++ b/tcg/aarch64/tcg-target.inc.c
> @@ -73,6 +73,18 @@ static inline void reloc_pc26(tcg_insn_unit *code_ptr,
> tcg_insn_unit *target)
> *code_ptr = deposit32(*code_ptr, 0, 26, offset);
> }
>
> +static inline void reloc_pc26_atomic(tcg_insn_unit *code_ptr,
> + tcg_insn_unit *target)
> +{
> + ptrdiff_t offset = target - code_ptr;
> + tcg_insn_unit insn;
> + assert(offset == sextract64(offset, 0, 26));
> + /* read instruction, mask away previous PC_REL26 parameter contents,
> + set the proper offset, then write back the instruction. */
This comment could be moved from here and reloc_pc26 and made common for
the two following functions.
> + insn = atomic_read(code_ptr);
> + atomic_set(code_ptr, deposit32(insn, 0, 26, offset));
> +}
> +
> static inline void reloc_pc19(tcg_insn_unit *code_ptr, tcg_insn_unit *target)
> {
> ptrdiff_t offset = target - code_ptr;
> @@ -835,7 +847,7 @@ void aarch64_tb_set_jmp_target(uintptr_t jmp_addr,
> uintptr_t addr)
> tcg_insn_unit *code_ptr = (tcg_insn_unit *)jmp_addr;
> tcg_insn_unit *target = (tcg_insn_unit *)addr;
>
> - reloc_pc26(code_ptr, target);
> + reloc_pc26_atomic(code_ptr, target);
> flush_icache_range(jmp_addr, jmp_addr + 4);
> }
Otherwise:
Reviewed-by: Alex Bennée <address@hidden>
--
Alex Bennée
Re: [Qemu-arm] [PATCH 08/11] tcg/aarch64: Make direct jump patching thread-safe, Sergey Fedorov, 2016/04/21