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Re: [Qemu-devel] [PATCH] exec.c: Fix subpage memory access to RAM Memory
From: |
Andreas Färber |
Subject: |
Re: [Qemu-devel] [PATCH] exec.c: Fix subpage memory access to RAM MemoryRegion |
Date: |
Tue, 29 Nov 2011 13:47:02 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111105 Thunderbird/8.0 |
Am 28.11.2011 16:06, schrieb Andreas Färber:
> Commit 95c318f5e1f88d7e5bcc6deac17330fd4806a2d3 (Fix segfault in mmio subpage
> handling code.) prevented a segfault by making all subpage registrations
> over an existing memory page perform an unassigned access. Symptoms were
> writes not taking effect and reads returning zero.
>
> Very small page sizes are not currently supported either, so subpage memory
> areas cannot fully be avoided.
>
> Therefore revert the previous fix and defer recognition of IO_MEM_RAM to
> subpage_{read,write}len() and translate any access there.
>
> Signed-off-by: Andreas Färber <address@hidden>
> Cc: Avi Kivity <address@hidden>
> Cc: Gleb Natapov <address@hidden>
> Cc: Blue Swirl <address@hidden>
> ---
> exec.c | 33 +++++++++++++++++++++++++++++++--
> 1 files changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index 6b92198..fba5ba1 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -3508,6 +3508,21 @@ static inline uint32_t subpage_readlen (subpage_t
> *mmio,
>
> addr += mmio->region_offset[idx];
> idx = mmio->sub_io_index[idx];
> + if (unlikely(idx == IO_MEM_RAM)) {
> + ram_addr_t raddr = /*mmio->base |*/ addr;
> + void *ptr = qemu_get_ram_ptr(raddr);
This...
> + switch (len) {
> + default:
> + case 0:
> + return ldub_p(ptr);
> + case 1:
> + return lduw_p(ptr);
> + case 2:
> + return ldl_p(ptr);
> + case 3:
> + return ldq_p(ptr);
> + }
> + }
> return io_mem_read[idx][len](io_mem_opaque[idx], addr);
> }
>
> @@ -3522,6 +3537,22 @@ static inline void subpage_writelen (subpage_t *mmio,
> target_phys_addr_t addr,
>
> addr += mmio->region_offset[idx];
> idx = mmio->sub_io_index[idx];
> + if (unlikely(idx == IO_MEM_RAM)) {
> + ram_addr_t raddr = /*mmio->base |*/ addr;
> + void *ptr = qemu_get_ram_ptr(raddr);
...and/or this seems to lead to "Bad RAM pointer" (or so) when there's
ELF code loaded into the subpage at that address despite being IO_MEM_RAM?
(Seen, e.g., if for RL78 I increase the page size from 12 to 16.)
> + switch (len) {
> + default:
> + case 0:
> + stb_p(ptr, value);
break;
> + case 1:
> + stw_p(ptr, value);
break;
> + case 2:
> + stl_p(ptr, value);
break;
> + case 3:
> + stq_p(ptr, value);
break;
Andreas
> + }
> + return;
> + }
> io_mem_write[idx][len](io_mem_opaque[idx], addr, value);
> }
>
> @@ -3583,8 +3614,6 @@ static int subpage_register (subpage_t *mmio, uint32_t
> start, uint32_t end,
> printf("%s: %p start %08x end %08x idx %08x eidx %08x mem %ld\n",
> __func__,
> mmio, start, end, idx, eidx, memory);
> #endif
> - if ((memory & ~TARGET_PAGE_MASK) == IO_MEM_RAM)
> - memory = IO_MEM_UNASSIGNED;
> memory = (memory >> IO_MEM_SHIFT) & (IO_MEM_NB_ENTRIES - 1);
> for (; idx <= eidx; idx++) {
> mmio->sub_io_index[idx] = memory;
--
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