Re: [PATCH 05/17] qemu: Respect length of watchpoints

[Jan Kiszka <jan.kiszka@web.de>]

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Avi Kivity wrote:
> Jan Kiszka wrote:
>> This adds length support for watchpoints. To keep things simple, only
>> aligned watchpoints are accepted.
>>
>> --- a/qemu/exec.c
>> +++ b/qemu/exec.c
>> @@ -1328,14 +1328,19 @@ static void breakpoint_invalidate(CPUSta
>>  int cpu_watchpoint_insert(CPUState *env, target_ulong addr,
>> target_ulong len,
>>                            int flags, CPUWatchpoint **watchpoint)
>>  {
>> +    target_ulong len_mask = ~(len - 1);
>>      CPUWatchpoint *wp;
>>  
>> +    /* sanity checks: allow power-of-2 lengths, deny unaligned
>> watchpoints */
>> +    if ((len != 1 && len != 2 && len != 4) || (addr & ~len_mask))
>> +        return -EINVAL;
>> +
>>   
> 
> It would be good to support 8-byte watchpoints (as x86-64 does); also,
> print a message if we deny a breakpoint due to bad alignment, so people
> know where to fix this.
> 

Yep, here the updated patch.

[ This, as well as the rest, for the convenience of testers under KVM.
  Will repost the updated QEMU series next week. ]

------------

This adds length support for watchpoints. To keep things simple, only
aligned watchpoints are accepted.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 qemu/cpu-defs.h |    2 +-
 qemu/exec.c     |   30 ++++++++++++++++++++----------
 2 files changed, 21 insertions(+), 11 deletions(-)

Index: b/qemu/exec.c
===================================================================
--- a/qemu/exec.c
+++ b/qemu/exec.c
@@ -1328,14 +1328,21 @@ static void breakpoint_invalidate(CPUSta
 int cpu_watchpoint_insert(CPUState *env, target_ulong addr, target_ulong len,
                           int flags, CPUWatchpoint **watchpoint)
 {
+    target_ulong len_mask = ~(len - 1);
     CPUWatchpoint *wp;
 
+    /* sanity checks: allow power-of-2 lengths, deny unaligned watchpoints */
+    if ((len != 1 && len != 2 && len != 4 && len != 8) || (addr & ~len_mask)) {
+        fprintf(stderr, "qemu: tried to set invalid watchpoint at "
+                TARGET_FMT_lx ", len=" TARGET_FMT_lu "\n", addr, len);
+        return -EINVAL;
+    }
     wp = qemu_malloc(sizeof(*wp));
     if (!wp)
         return -ENOBUFS;
 
     wp->vaddr = addr;
-    wp->len = len;
+    wp->len_mask = len_mask;
     wp->flags = flags;
 
     wp->next = env->watchpoints;
@@ -1359,10 +1366,12 @@ int cpu_watchpoint_insert(CPUState *env,
 int cpu_watchpoint_remove(CPUState *env, target_ulong addr, target_ulong len,
                           int flags)
 {
+    target_ulong len_mask = ~(len - 1);
     CPUWatchpoint *wp;
 
     for (wp = env->watchpoints; wp != NULL; wp = wp->next) {
-        if (addr == wp->vaddr && len == wp->len && flags == wp->flags) {
+        if (addr == wp->vaddr && len_mask == wp->len_mask
+                && flags == wp->flags) {
             cpu_watchpoint_remove_by_ref(env, wp);
             return 0;
         }
@@ -2490,7 +2499,7 @@ static CPUWriteMemoryFunc *notdirty_mem_
 };
 
 /* Generate a debug exception if a watchpoint has been hit.  */
-static void check_watchpoint(int offset, int flags)
+static void check_watchpoint(int offset, int len_mask, int flags)
 {
     CPUState *env = cpu_single_env;
     target_ulong vaddr;
@@ -2498,7 +2507,8 @@ static void check_watchpoint(int offset,
 
     vaddr = (env->mem_io_vaddr & TARGET_PAGE_MASK) + offset;
     for (wp = env->watchpoints; wp != NULL; wp = wp->next) {
-        if (vaddr == wp->vaddr && (wp->flags & flags)) {
+        if ((vaddr == (wp->vaddr & len_mask) ||
+             (vaddr & wp->len_mask) == wp->vaddr) && (wp->flags & flags)) {
             env->watchpoint_hit = wp;
             cpu_interrupt(env, CPU_INTERRUPT_DEBUG);
             break;
@@ -2511,40 +2521,40 @@ static void check_watchpoint(int offset,
    phys routines.  */
 static uint32_t watch_mem_readb(void *opaque, target_phys_addr_t addr)
 {
-    check_watchpoint(addr & ~TARGET_PAGE_MASK, BP_MEM_READ);
+    check_watchpoint(addr & ~TARGET_PAGE_MASK, ~0x0, BP_MEM_READ);
     return ldub_phys(addr);
 }
 
 static uint32_t watch_mem_readw(void *opaque, target_phys_addr_t addr)
 {
-    check_watchpoint(addr & ~TARGET_PAGE_MASK, BP_MEM_READ);
+    check_watchpoint(addr & ~TARGET_PAGE_MASK, ~0x1, BP_MEM_READ);
     return lduw_phys(addr);
 }
 
 static uint32_t watch_mem_readl(void *opaque, target_phys_addr_t addr)
 {
-    check_watchpoint(addr & ~TARGET_PAGE_MASK, BP_MEM_READ);
+    check_watchpoint(addr & ~TARGET_PAGE_MASK, ~0x3, BP_MEM_READ);
     return ldl_phys(addr);
 }
 
 static void watch_mem_writeb(void *opaque, target_phys_addr_t addr,
                              uint32_t val)
 {
-    check_watchpoint(addr & ~TARGET_PAGE_MASK, BP_MEM_WRITE);
+    check_watchpoint(addr & ~TARGET_PAGE_MASK, ~0x0, BP_MEM_WRITE);
     stb_phys(addr, val);
 }
 
 static void watch_mem_writew(void *opaque, target_phys_addr_t addr,
                              uint32_t val)
 {
-    check_watchpoint(addr & ~TARGET_PAGE_MASK, BP_MEM_WRITE);
+    check_watchpoint(addr & ~TARGET_PAGE_MASK, ~0x1, BP_MEM_WRITE);
     stw_phys(addr, val);
 }
 
 static void watch_mem_writel(void *opaque, target_phys_addr_t addr,
                              uint32_t val)
 {
-    check_watchpoint(addr & ~TARGET_PAGE_MASK, BP_MEM_WRITE);
+    check_watchpoint(addr & ~TARGET_PAGE_MASK, ~0x3, BP_MEM_WRITE);
     stl_phys(addr, val);
 }
 
Index: b/qemu/cpu-defs.h
===================================================================
--- a/qemu/cpu-defs.h
+++ b/qemu/cpu-defs.h
@@ -148,7 +148,7 @@ typedef struct CPUBreakpoint {
 
 typedef struct CPUWatchpoint {
     target_ulong vaddr;
-    target_ulong len;
+    target_ulong len_mask;
     int flags; /* BP_* */
     struct CPUWatchpoint *prev, *next;
 } CPUWatchpoint;


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