From a738ea1d41daeec0cccb4ab6671f4f6d53bd9e18 Mon Sep 17 00:00:00 2001 From: Yao Qi Date: Fri, 8 Dec 2017 17:27:03 +0000 Subject: Clear non-significant bits of address on memory access ARMv8 supports tagged address, that is, the top one byte in address is ignored. It is always enabled on aarch64-linux. See https://www.kernel.org/doc/Documentation/arm64/tagged-pointers.txt The tag in the tagged address is modeled as non-significant bits in address, so this patch adds a new gdbarch method significant_addr_bit and clear the non-significant bits (the top byte in ARMv8) of the virtual address at the point before passing address to target cache layer. IOW, the address used in the target cache layer is already cleared. Before this patch, (gdb) x/x 0x0000000000411030 0x411030 : 0x00000000 (gdb) x/x 0xf000000000411030 0xf000000000411030: Cannot access memory at address 0xf000000000411030 After this patch, (gdb) x/x 0x0000000000411030 0x411030 : 0x00000000 (gdb) x/x 0xf000000000411030 0xf000000000411030: 0x00000000 Note that I used address_significant in paddress, but it causes a regression gdb.base/long_long.exp, because gdb clears the non-significant bits in address, but test still expects them. p/a val.oct^M $24 = 0x2ee53977053977^M (gdb) FAIL: gdb.base/long_long.exp: p/a val.oct so I defer the change there. gdb: 2017-12-08 Yao Qi * aarch64-tdep.c (aarch64_gdbarch_init): Install gdbarch significant_addr_bit. * gdbarch.sh (significant_addr_bit): New. * gdbarch.c, gdbarch.h: Re-generated. * target.c (memory_xfer_partial): Call address_significant. * utils.c (address_significant): New function. * utils.h (address_significant): Declare. 2017-12-08 Yao Qi gdb/testsuite: * gdb.arch/aarch64-tagged-pointer.c: New file. * gdb.arch/aarch64-tagged-pointer.exp: New file. --- gdb/target.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'gdb/target.c') diff --git a/gdb/target.c b/gdb/target.c index 3b8b8ea2186..767a2ad45ac 100644 --- a/gdb/target.c +++ b/gdb/target.c @@ -1214,6 +1214,8 @@ memory_xfer_partial (struct target_ops *ops, enum target_object object, if (len == 0) return TARGET_XFER_EOF; + memaddr = address_significant (target_gdbarch (), memaddr); + /* Fill in READBUF with breakpoint shadows, or WRITEBUF with breakpoint insns, thus hiding out from higher layers whether there are software breakpoints inserted in the code stream. */ -- cgit v1.2.1