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authorYao Qi <yao.qi@linaro.org>2017-12-08 17:27:03 +0000
committerYao Qi <yao.qi@linaro.org>2017-12-08 17:27:03 +0000
commita738ea1d41daeec0cccb4ab6671f4f6d53bd9e18 (patch)
tree774250556f5e1468e539e5726014a277d17f6327 /gdb/gdbarch.sh
parentC++-ify parse_format_string (diff)
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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 <global>: 0x00000000 (gdb) x/x 0xf000000000411030 0xf000000000411030: Cannot access memory at address 0xf000000000411030 After this patch, (gdb) x/x 0x0000000000411030 0x411030 <global>: 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 <yao.qi@linaro.org> * 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 <yao.qi@linaro.org> gdb/testsuite: * gdb.arch/aarch64-tagged-pointer.c: New file. * gdb.arch/aarch64-tagged-pointer.exp: New file.
Diffstat (limited to 'gdb/gdbarch.sh')
-rwxr-xr-xgdb/gdbarch.sh6
1 files changed, 6 insertions, 0 deletions
diff --git a/gdb/gdbarch.sh b/gdb/gdbarch.sh
index 6459b12747b..1f165cf11ba 100755
--- a/gdb/gdbarch.sh
+++ b/gdb/gdbarch.sh
@@ -621,6 +621,12 @@ m;CORE_ADDR;convert_from_func_ptr_addr;CORE_ADDR addr, struct target_ops *targ;a
# possible it should be in TARGET_READ_PC instead).
m;CORE_ADDR;addr_bits_remove;CORE_ADDR addr;addr;;core_addr_identity;;0
+# On some machines, not all bits of an address word are significant.
+# For example, on AArch64, the top bits of an address known as the "tag"
+# are ignored by the kernel, the hardware, etc. and can be regarded as
+# additional data associated with the address.
+v;int;significant_addr_bit;;;;;gdbarch_addr_bit (gdbarch);
+
# FIXME/cagney/2001-01-18: This should be split in two. A target method that
# indicates if the target needs software single step. An ISA method to
# implement it.