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Re: [Qemu-devel] [PATCH 4/5] ARM BE32 watchpoint fix.
From: |
Julian Brown |
Subject: |
Re: [Qemu-devel] [PATCH 4/5] ARM BE32 watchpoint fix. |
Date: |
Tue, 6 Dec 2016 15:12:29 +0000 |
On Fri, 4 Nov 2016 09:55:17 +0100
Paolo Bonzini <address@hidden> wrote:
> On 04/11/2016 00:20, Julian Brown wrote:
> > On Thu, 3 Nov 2016 23:14:05 +0000
> > Peter Maydell <address@hidden> wrote:
> >
> >> On 3 November 2016 at 17:30, Julian Brown <address@hidden>
> >> wrote:
> >>> In BE32 mode, sub-word size watchpoints can fail to trigger
> >>> because the address of the access is adjusted in the opcode
> >>> helpers before being compared with the watchpoint registers.
> >>> This patch reversed the address adjustment before performing the
> >>> comparison.
> >>>
> >>> Signed-off-by: Julian Brown <address@hidden>
> >>> ---
> >>> exec.c | 13 +++++++++++++
> >>> 1 file changed, 13 insertions(+)
> >>>
> >>> diff --git a/exec.c b/exec.c
> >>> index 4c84389..eadab54 100644
> >>> --- a/exec.c
> >>> +++ b/exec.c
> >>> @@ -2047,6 +2047,19 @@ static void check_watchpoint(int offset,
> >>> int len, MemTxAttrs attrs, int flags) return;
> >>> }
> >>> vaddr = (cpu->mem_io_vaddr & TARGET_PAGE_MASK) + offset;
> >>> +#if defined(TARGET_ARM) && !defined(CONFIG_USER_ONLY)
> >>> + /* In BE32 system mode, target memory is stored byteswapped
> >>> (FIXME:
> >>> + relative to a little-endian host system), and by the time
> >>> we reach here
> >>> + (via an opcode helper) the addresses of subword accesses
> >>> have been
> >>> + adjusted to account for that, which means that watchpoints
> >>> will not
> >>> + match. Undo the adjustment here. */
> >>> + if (arm_sctlr_b(env)) {
> >>> + if (len == 1)
> >>> + vaddr ^= 3;
> >>> + else if (len == 2)
> >>> + vaddr ^= 2;
> >>> + }
> >>> +#endif
> >>
> >> No target-CPU specific code in exec.c, please...
> >
> > Yeah, I'd imagine not. I struggled with this one. Any suggestions
> > for a better way to do this?
>
> You can add a function pointer to CPUClass and call it from here.
> It's how cc->debug_check_watchpoint is being called already.
How's this? There's still some grubbiness, but it's mostly confined to
the ARM backend code.
Thanks,
Julian
0003-ARM-BE32-watchpoint-fix.patch
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