On 3/17/20 4:38 PM, Christophe Leroy wrote:
Le 09/03/2020 à 09:58, Ravi Bangoria a écrit :
ptrace and perf watchpoints on powerpc behaves differently. Ptrace
On the 8xx, ptrace generates signal after executing the instruction.
8xx logic is unchanged. I should have mentioned "Book3s DAWR".
watchpoint works in one-shot mode and generates signal before executing
instruction. It's ptrace user's job to single-step the instruction and
re-enable the watchpoint. OTOH, in case of perf watchpoint, kernel
emulates/single-steps the instruction and then generates event. If perf
and ptrace creates two events with same or overlapping address ranges,
it's ambiguous to decide who should single-step the instruction. Because
of this issue ptrace and perf event can't coexist when the address range
overlaps.
Ok, and then ? What's the purpose of this (big) patch ?
Don't allow perf and ptrace watchpoint at the same time if their address
range overlaps.
...
+struct breakpoint {
+ struct list_head list;
+ struct perf_event *bp;
+ bool ptrace_bp;
+};
Don't we have an equivalent struct already ?
No. Using this we track percpu and perthread watchpoints for both perf and
ptrace. This problems is powerpc(DAWR) specific and thus we need to hook arch
specific logic in watchopint installation/uninstallation path.
...
+static bool bp_addr_range_overlap(struct perf_event *bp1, struct perf_event
*bp2)
+{
+ __u64 bp1_saddr, bp1_eaddr, bp2_saddr, bp2_eaddr;
+
+ bp1_saddr = bp1->attr.bp_addr & ~HW_BREAKPOINT_ALIGN;
+ bp1_eaddr = (bp1->attr.bp_addr + bp1->attr.bp_len - 1) |
HW_BREAKPOINT_ALIGN;
+ bp2_saddr = bp2->attr.bp_addr & ~HW_BREAKPOINT_ALIGN;
+ bp2_eaddr = (bp2->attr.bp_addr + bp2->attr.bp_len - 1) |
HW_BREAKPOINT_ALIGN;
+
+ return (bp1_saddr <= bp2_eaddr && bp1_eaddr >= bp2_saddr);
Would be better with something like (HW_BREAKPOINT_SIZE needs to be defined).
bp1_saddr = ALIGN_DOWN(bp1->attr.bp_addr, HW_BREAKPOINT_SIZE);
bp1_eaddr = ALIGN(bp1->attr.bp_addr, HW_BREAKPOINT_SIZE);
bp2_saddr = ALIGN_DOWN(bp2->attr.bp_addr, HW_BREAKPOINT_SIZE);
bp2_eaddr = ALIGN(bp2->attr.bp_addr, HW_BREAKPOINT_SIZE);
return (bp1_saddr < bp2_eaddr && bp1_eaddr > bp2_saddr);
Ok.
Thanks,
Ravi
