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This > constant represents the number of address bits in a pointer. > > Right now AArch64 is the only architecture that uses it, and 56 was a > correct option so far. > > But if we are using Pointer Authentication (PAuth), we might use up to 2 bytes > from the address space to store the required information. We could also have > cases where we're using both PAuth and MTE. > > We could adjust the constant to 48 to cover those cases, but this doesn't > cover the case where GDB needs to sign-extend kernel addresses after removal > of the non-address bits. > > This has worked so far because bit 55 is used to select between kernel-space > and user-space addresses. But trying to clear a range of bits crossing the > bit 55 boundary requires the hook to be smarter. > > The following patch renames the gdbarch hook from significant_addr_bit to > remove_non_address_bits and passes a pointer as opposed to the number of > bits. The hook is now responsible for removing the required non-address bits > and sign-extending the address if needed. > > While at it, make GDB and GDBServer share some more code for aarch64 and add a > new arch-specific testcase gdb.arch/aarch64-non-address-bits.exp. > > Bug-url: https://sourceware.org/bugzilla/show_bug.cgi?id=28947 > --- > gdb/aarch64-linux-nat.c | 2 +- > gdb/aarch64-linux-tdep.c | 55 +++++++- > gdb/arch-utils.c | 8 ++ > gdb/arch-utils.h | 4 + > gdb/arch/aarch64.c | 27 ++++ > gdb/arch/aarch64.h | 17 +++ > gdb/breakpoint.c | 6 +- > gdb/gdbarch-components.py | 22 +++- > gdb/gdbarch-gen.h | 21 ++- > gdb/gdbarch.c | 25 ++-- > gdb/target.c | 2 +- > .../gdb.arch/aarch64-non-address-bits.c | 25 ++++ > .../gdb.arch/aarch64-non-address-bits.exp | 121 ++++++++++++++++++ > gdb/utils.c | 22 ---- > gdb/utils.h | 3 - > gdbserver/linux-aarch64-low.cc | 39 ++++-- > 16 files changed, 326 insertions(+), 73 deletions(-) > create mode 100644 gdb/testsuite/gdb.arch/aarch64-non-address-bits.c > create mode 100644 gdb/testsuite/gdb.arch/aarch64-non-address-bits.exp > > diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c > index eda79ec6d35..06c7c6198ef 100644 > --- a/gdb/aarch64-linux-nat.c > +++ b/gdb/aarch64-linux-nat.c > @@ -843,7 +843,7 @@ aarch64_linux_nat_target::stopped_data_address (CORE_ADDR *addr_p) > kernel can potentially be tagged addresses. */ > struct gdbarch *gdbarch = thread_architecture (inferior_ptid); > const CORE_ADDR addr_trap > - = address_significant (gdbarch, (CORE_ADDR) siginfo.si_addr); > + = gdbarch_remove_non_address_bits (gdbarch, (CORE_ADDR) siginfo.si_addr); > > /* Check if the address matches any watched address. */ > state = aarch64_get_debug_reg_state (inferior_ptid.pid ()); > diff --git a/gdb/aarch64-linux-tdep.c b/gdb/aarch64-linux-tdep.c > index 15773c75da8..279c8d98f5d 100644 > --- a/gdb/aarch64-linux-tdep.c > +++ b/gdb/aarch64-linux-tdep.c > @@ -1591,7 +1591,7 @@ aarch64_linux_tagged_address_p (struct gdbarch *gdbarch, struct value *address) > CORE_ADDR addr = value_as_address (address); > > /* Remove the top byte for the memory range check. */ > - addr = address_significant (gdbarch, addr); > + addr = gdbarch_remove_non_address_bits (gdbarch, addr); > > /* Check if the page that contains ADDRESS is mapped with PROT_MTE. */ > if (!linux_address_in_memtag_page (addr)) > @@ -1617,7 +1617,7 @@ aarch64_linux_memtag_matches_p (struct gdbarch *gdbarch, > > /* Fetch the allocation tag for ADDRESS. */ > gdb::optional atag > - = aarch64_mte_get_atag (address_significant (gdbarch, addr)); > + = aarch64_mte_get_atag (gdbarch_remove_non_address_bits (gdbarch, addr)); > > if (!atag.has_value ()) > return true; > @@ -1656,7 +1656,7 @@ aarch64_linux_set_memtags (struct gdbarch *gdbarch, struct value *address, > else > { > /* Remove the top byte. */ > - addr = address_significant (gdbarch, addr); > + addr = gdbarch_remove_non_address_bits (gdbarch, addr); > > /* Make sure we are dealing with a tagged address to begin with. */ > if (!aarch64_linux_tagged_address_p (gdbarch, address)) > @@ -1713,7 +1713,7 @@ aarch64_linux_get_memtag (struct gdbarch *gdbarch, struct value *address, > return nullptr; > > /* Remove the top byte. */ > - addr = address_significant (gdbarch, addr); > + addr = gdbarch_remove_non_address_bits (gdbarch, addr); > gdb::optional atag = aarch64_mte_get_atag (addr); > > if (!atag.has_value ()) > @@ -1787,7 +1787,8 @@ aarch64_linux_report_signal_info (struct gdbarch *gdbarch, > uiout->text ("\n"); > > gdb::optional atag > - = aarch64_mte_get_atag (address_significant (gdbarch, fault_addr)); > + = aarch64_mte_get_atag (gdbarch_remove_non_address_bits (gdbarch, > + fault_addr)); > gdb_byte ltag = aarch64_mte_get_ltag (fault_addr); > > if (!atag.has_value ()) > @@ -1961,6 +1962,47 @@ aarch64_linux_decode_memtag_section (struct gdbarch *gdbarch, > return tags; > } > > +/* AArch64 implementation of the remove_non_address_bits gdbarch hook. Remove > + non address bits from a pointer value. */ > + > +static CORE_ADDR > +aarch64_remove_non_address_bits (struct gdbarch *gdbarch, CORE_ADDR pointer) > +{ > + aarch64_gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); > + > + /* By default, we assume TBI and discard the top 8 bits plus the VA range > + select bit (55). */ > + CORE_ADDR mask = AARCH64_TOP_BITS_MASK; > + > + if (tdep->has_pauth ()) > + { > + /* Fetch the PAC masks. These masks are per-process, so we can just > + fetch data from whatever thread we have at the moment. > + > + Also, we have both a code mask and a data mask. For now they are the > + same, but this may change in the future. */ > + struct regcache *regs = get_current_regcache (); > + CORE_ADDR cmask, dmask; > + > + if (regs->cooked_read (tdep->pauth_reg_base, &dmask) != REG_VALID) > + dmask = mask; > + > + if (regs->cooked_read (tdep->pauth_reg_base + 1, &cmask) != REG_VALID) > + cmask = mask; > + > + if (dmask != cmask) > + { > + /* Warn if the masks are different. */ > + aarch64_pauth_mask_warning (); > + mask |= dmask > cmask? dmask : cmask; > + } > + else > + mask |= cmask; > + } > + > + return aarch64_remove_top_bits (pointer, mask); > +} > + > static void > aarch64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) > { > @@ -2016,7 +2058,8 @@ aarch64_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch) > /* The top byte of a user space address known as the "tag", > is ignored by the kernel and can be regarded as additional > data associated with the address. */ > - set_gdbarch_significant_addr_bit (gdbarch, 56); > + set_gdbarch_remove_non_address_bits (gdbarch, > + aarch64_remove_non_address_bits); > > /* MTE-specific settings and hooks. */ > if (tdep->has_mte ()) > diff --git a/gdb/arch-utils.c b/gdb/arch-utils.c > index 9bd4f0ddae6..12ed38ce6a9 100644 > --- a/gdb/arch-utils.c > +++ b/gdb/arch-utils.c > @@ -82,6 +82,14 @@ legacy_register_sim_regno (struct gdbarch *gdbarch, int regnum) > return LEGACY_SIM_REGNO_IGNORE; > } > > +/* See arch-utils.h */ > + > +CORE_ADDR > +default_remove_non_address_bits (struct gdbarch *gdbarch, CORE_ADDR pointer) > +{ > + /* By default, just return the pointer value. */ > + return pointer; > +} > > /* See arch-utils.h */ > > diff --git a/gdb/arch-utils.h b/gdb/arch-utils.h > index f850e5fd6e7..e117599b171 100644 > --- a/gdb/arch-utils.h > +++ b/gdb/arch-utils.h > @@ -132,6 +132,10 @@ extern const struct floatformat ** > default_floatformat_for_type (struct gdbarch *gdbarch, > const char *name, int len); > > +/* Default implementation of gdbarch_remove_non_address_bits. */ > +CORE_ADDR default_remove_non_address_bits (struct gdbarch *gdbarch, > + CORE_ADDR pointer); > + > /* Default implementation of gdbarch_memtag_to_string. */ > extern std::string default_memtag_to_string (struct gdbarch *gdbarch, > struct value *tag); > diff --git a/gdb/arch/aarch64.c b/gdb/arch/aarch64.c > index 0f73286f145..d9c4b994850 100644 > --- a/gdb/arch/aarch64.c > +++ b/gdb/arch/aarch64.c > @@ -58,3 +58,30 @@ aarch64_create_target_description (const aarch64_features &features) > > return tdesc.release (); > } > + > +/* See arch/aarch64.h. */ > + > +CORE_ADDR > +aarch64_remove_top_bits (CORE_ADDR pointer, CORE_ADDR mask) > +{ > + /* The VA range select bit is 55. This bit tells us if we have a > + kernel-space address or a user-space address. */ > + bool kernel_address = (pointer & VA_RANGE_SELECT_BIT_MASK) != 0; > + > + /* Remove the top non-address bits. */ > + pointer &= ~mask; > + > + /* Sign-extend if we have a kernel-space address. */ > + if (kernel_address) > + pointer |= mask; > + > + return pointer; > +} > + > +/* See arch/aarch64.h. */ > + > +void > +aarch64_pauth_mask_warning () > +{ > + warning (_("Pointer authentication masks for code (C) and data (D) differ")); > +} > diff --git a/gdb/arch/aarch64.h b/gdb/arch/aarch64.h > index 8e3fd36726a..19a3fb4d7c0 100644 > --- a/gdb/arch/aarch64.h > +++ b/gdb/arch/aarch64.h > @@ -67,6 +67,16 @@ namespace std > target_desc * > aarch64_create_target_description (const aarch64_features &features); > > +/* Given a pointer value POINTER and a MASK of non-address bits, remove the > + non-address bits from the pointer and sign-extend the result if required. > + The sign-extension is required so we can handle kernel addresses > + correctly. */ > +CORE_ADDR aarch64_remove_top_bits (CORE_ADDR pointer, CORE_ADDR mask); > + > +/* Produce a warning stating the D mask and the C mask have different > + values. */ > +void aarch64_pauth_mask_warning (); > + > /* Register numbers of various important registers. > Note that on SVE, the Z registers reuse the V register numbers and the V > registers become pseudo registers. */ > @@ -96,6 +106,9 @@ enum aarch64_regnum > AARCH64_LAST_V_ARG_REGNUM = AARCH64_V0_REGNUM + 7 > }; > > +/* Bit 55 is used to select between a kernel-space and user-space address. */ > +#define VA_RANGE_SELECT_BIT_MASK 0x80000000000000 > + > #define V_REGISTER_SIZE 16 > > /* Pseudo register base numbers. */ > @@ -143,4 +156,8 @@ enum aarch64_regnum > /* Maximum supported VQ value. Increase if required. */ > #define AARCH64_MAX_SVE_VQ 16 > > +/* Mask with 1's in bits 55~63, used to remove the top byte of pointers > + (Top Byte Ignore). */ > +#define AARCH64_TOP_BITS_MASK (~((((CORE_ADDR) 1) << (64 - 9)) - 1)) > + > #endif /* ARCH_AARCH64_H */ > diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c > index 2fe74ea0d3a..c26271017af 100644 > --- a/gdb/breakpoint.c > +++ b/gdb/breakpoint.c > @@ -2112,7 +2112,8 @@ update_watchpoint (struct watchpoint *b, int reparse) > loc->gdbarch = value_type (v)->arch (); > > loc->pspace = frame_pspace; > - loc->address = address_significant (loc->gdbarch, addr); > + loc->address > + = gdbarch_remove_non_address_bits (loc->gdbarch, addr); > > if (bitsize != 0) > { > @@ -7161,7 +7162,8 @@ adjust_breakpoint_address (struct gdbarch *gdbarch, > = gdbarch_adjust_breakpoint_address (gdbarch, bpaddr); > } > > - adjusted_bpaddr = address_significant (gdbarch, adjusted_bpaddr); > + adjusted_bpaddr > + = gdbarch_remove_non_address_bits (gdbarch, adjusted_bpaddr); > > /* An adjusted breakpoint address can significantly alter > a user's expectations. Print a warning if an adjustment > diff --git a/gdb/gdbarch-components.py b/gdb/gdbarch-components.py > index 71aa5991fbe..25b6d69d2d9 100644 > --- a/gdb/gdbarch-components.py > +++ b/gdb/gdbarch-components.py > @@ -1116,15 +1116,23 @@ possible it should be in TARGET_READ_PC instead). > invalid=False, > ) > > -Value( > +Method( > comment=""" > -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. > +On some architectures, not all bits of a pointer are significant. > +On AArch64, for example, the top bits of a pointer may carry a "tag", which > +can be ignored by the kernel and the hardware. The "tag" can be regarded as > +additional data associated with the pointer, but it is not part of the address. > + > +Given a pointer for the architecture, this hook removes all the > +non-significant bits and sign-extends things as needed. It gets used to remove > +non-address bits from data pointers (for example, removing the AArch64 MTE tag > +bits from a pointer) and from code pointers (removing the AArch64 PAC signature > +from a pointer containing the return address). > """, > - type="int", > - name="significant_addr_bit", > + type="CORE_ADDR", > + name="remove_non_address_bits", > + params=[("CORE_ADDR", "pointer")], > + predefault="default_remove_non_address_bits", > invalid=False, > ) > > diff --git a/gdb/gdbarch-gen.h b/gdb/gdbarch-gen.h > index 0504962e50d..99909946fb9 100644 > --- a/gdb/gdbarch-gen.h > +++ b/gdb/gdbarch-gen.h > @@ -609,13 +609,20 @@ typedef CORE_ADDR (gdbarch_addr_bits_remove_ftype) (struct gdbarch *gdbarch, COR > extern CORE_ADDR gdbarch_addr_bits_remove (struct gdbarch *gdbarch, CORE_ADDR addr); > extern void set_gdbarch_addr_bits_remove (struct gdbarch *gdbarch, gdbarch_addr_bits_remove_ftype *addr_bits_remove); > > -/* 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. */ > - > -extern int gdbarch_significant_addr_bit (struct gdbarch *gdbarch); > -extern void set_gdbarch_significant_addr_bit (struct gdbarch *gdbarch, int significant_addr_bit); > +/* On some architectures, not all bits of a pointer are significant. > + On AArch64, for example, the top bits of a pointer may carry a "tag", which > + can be ignored by the kernel and the hardware. The "tag" can be regarded as > + additional data associated with the pointer, but it is not part of the address. > + > + Given a pointer for the architecture, this hook removes all the > + non-significant bits and sign-extends things as needed. It gets used to remove > + non-address bits from data pointers (for example, removing the AArch64 MTE tag > + bits from a pointer) and from code pointers (removing the AArch64 PAC signature > + from a pointer containing the return address). */ > + > +typedef CORE_ADDR (gdbarch_remove_non_address_bits_ftype) (struct gdbarch *gdbarch, CORE_ADDR pointer); > +extern CORE_ADDR gdbarch_remove_non_address_bits (struct gdbarch *gdbarch, CORE_ADDR pointer); > +extern void set_gdbarch_remove_non_address_bits (struct gdbarch *gdbarch, gdbarch_remove_non_address_bits_ftype *remove_non_address_bits); > > /* Return a string representation of the memory tag TAG. */ > > diff --git a/gdb/gdbarch.c b/gdb/gdbarch.c > index 0edae7f6f0a..b087aacd57e 100644 > --- a/gdb/gdbarch.c > +++ b/gdb/gdbarch.c > @@ -142,7 +142,7 @@ struct gdbarch > int frame_red_zone_size = 0; > gdbarch_convert_from_func_ptr_addr_ftype *convert_from_func_ptr_addr = nullptr; > gdbarch_addr_bits_remove_ftype *addr_bits_remove = nullptr; > - int significant_addr_bit = 0; > + gdbarch_remove_non_address_bits_ftype *remove_non_address_bits = nullptr; > gdbarch_memtag_to_string_ftype *memtag_to_string = nullptr; > gdbarch_tagged_address_p_ftype *tagged_address_p = nullptr; > gdbarch_memtag_matches_p_ftype *memtag_matches_p = nullptr; > @@ -324,6 +324,7 @@ gdbarch_alloc (const struct gdbarch_info *info, > gdbarch->stabs_argument_has_addr = default_stabs_argument_has_addr; > gdbarch->convert_from_func_ptr_addr = convert_from_func_ptr_addr_identity; > gdbarch->addr_bits_remove = core_addr_identity; > + gdbarch->remove_non_address_bits = default_remove_non_address_bits; > gdbarch->memtag_to_string = default_memtag_to_string; > gdbarch->tagged_address_p = default_tagged_address_p; > gdbarch->memtag_matches_p = default_memtag_matches_p; > @@ -493,7 +494,7 @@ verify_gdbarch (struct gdbarch *gdbarch) > /* Skip verify of frame_red_zone_size, invalid_p == 0 */ > /* Skip verify of convert_from_func_ptr_addr, invalid_p == 0 */ > /* Skip verify of addr_bits_remove, invalid_p == 0 */ > - /* Skip verify of significant_addr_bit, invalid_p == 0 */ > + /* Skip verify of remove_non_address_bits, invalid_p == 0 */ > /* Skip verify of memtag_to_string, invalid_p == 0 */ > /* Skip verify of tagged_address_p, invalid_p == 0 */ > /* Skip verify of memtag_matches_p, invalid_p == 0 */ > @@ -974,8 +975,8 @@ gdbarch_dump (struct gdbarch *gdbarch, struct ui_file *file) > "gdbarch_dump: addr_bits_remove = <%s>\n", > host_address_to_string (gdbarch->addr_bits_remove)); > gdb_printf (file, > - "gdbarch_dump: significant_addr_bit = %s\n", > - plongest (gdbarch->significant_addr_bit)); > + "gdbarch_dump: remove_non_address_bits = <%s>\n", > + host_address_to_string (gdbarch->remove_non_address_bits)); > gdb_printf (file, > "gdbarch_dump: memtag_to_string = <%s>\n", > host_address_to_string (gdbarch->memtag_to_string)); > @@ -3165,21 +3166,21 @@ set_gdbarch_addr_bits_remove (struct gdbarch *gdbarch, > gdbarch->addr_bits_remove = addr_bits_remove; > } > > -int > -gdbarch_significant_addr_bit (struct gdbarch *gdbarch) > +CORE_ADDR > +gdbarch_remove_non_address_bits (struct gdbarch *gdbarch, CORE_ADDR pointer) > { > gdb_assert (gdbarch != NULL); > - /* Skip verify of significant_addr_bit, invalid_p == 0 */ > + gdb_assert (gdbarch->remove_non_address_bits != NULL); > if (gdbarch_debug >= 2) > - gdb_printf (gdb_stdlog, "gdbarch_significant_addr_bit called\n"); > - return gdbarch->significant_addr_bit; > + gdb_printf (gdb_stdlog, "gdbarch_remove_non_address_bits called\n"); > + return gdbarch->remove_non_address_bits (gdbarch, pointer); > } > > void > -set_gdbarch_significant_addr_bit (struct gdbarch *gdbarch, > - int significant_addr_bit) > +set_gdbarch_remove_non_address_bits (struct gdbarch *gdbarch, > + gdbarch_remove_non_address_bits_ftype remove_non_address_bits) > { > - gdbarch->significant_addr_bit = significant_addr_bit; > + gdbarch->remove_non_address_bits = remove_non_address_bits; > } > > std::string > diff --git a/gdb/target.c b/gdb/target.c > index 41144901fc1..47a2195c667 100644 > --- a/gdb/target.c > +++ b/gdb/target.c > @@ -1644,7 +1644,7 @@ memory_xfer_partial (struct target_ops *ops, enum target_object object, > if (len == 0) > return TARGET_XFER_EOF; > > - memaddr = address_significant (target_gdbarch (), memaddr); > + memaddr = gdbarch_remove_non_address_bits (target_gdbarch (), memaddr); > > /* Fill in READBUF with breakpoint shadows, or WRITEBUF with > breakpoint insns, thus hiding out from higher layers whether > diff --git a/gdb/testsuite/gdb.arch/aarch64-non-address-bits.c b/gdb/testsuite/gdb.arch/aarch64-non-address-bits.c > new file mode 100644 > index 00000000000..3cf6d63da17 > --- /dev/null > +++ b/gdb/testsuite/gdb.arch/aarch64-non-address-bits.c > @@ -0,0 +1,25 @@ > +/* This file is part of GDB, the GNU debugger. > + > + Copyright 2022 Free Software Foundation, Inc. > + > + This program is free software; you can redistribute it and/or modify > + it under the terms of the GNU General Public License as published by > + the Free Software Foundation; either version 3 of the License, or > + (at your option) any later version. > + > + This program is distributed in the hope that it will be useful, > + but WITHOUT ANY WARRANTY; without even the implied warranty of > + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + GNU General Public License for more details. > + > + You should have received a copy of the GNU General Public License > + along with this program. If not, see . */ > + > +static long l = 0; > +static long *l_ptr = &l; > + > +int > +main (int argc, char **argv) > +{ > + return *l_ptr; > +} > diff --git a/gdb/testsuite/gdb.arch/aarch64-non-address-bits.exp b/gdb/testsuite/gdb.arch/aarch64-non-address-bits.exp > new file mode 100644 > index 00000000000..2b5a7b2f517 > --- /dev/null > +++ b/gdb/testsuite/gdb.arch/aarch64-non-address-bits.exp > @@ -0,0 +1,121 @@ > +# Copyright 2022 Free Software Foundation, Inc. > +# > +# This program is free software; you can redistribute it and/or modify > +# it under the terms of the GNU General Public License as published by > +# the Free Software Foundation; either version 3 of the License, or > +# (at your option) any later version. > +# > +# This program is distributed in the hope that it will be useful, > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > +# GNU General Public License for more details. > +# > +# You should have received a copy of the GNU General Public License > +# along with this program. If not, see . > +# > +# This file is part of the gdb testsuite. > +# > +# Test that GDB for AArch64/Linux can properly handle pointers with > +# the upper 16 bits (PAC) or 8 bits (Tag) set, as well as the > +# VA_RANGE_SELECT bit (55). > + > +if {![is_aarch64_target]} { > + verbose "Skipping ${gdb_test_file_name}." > + return > +} > + > +global hex > +global decimal > + > +standard_testfile > +if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } { > + return -1 > +} > + > +if ![runto_main] { > + return -1 > +} > + > +# We need to iterate over two distinct ranges, separated by a single bit. > +# This bit is 55 (VA_RANGE_SELECT) which tells us if we have a kernel-space > +# address or a user-space address. > + > +# The tag field has 8 bits. > +set tag_bits_count 8 > + > +# The pac field has 7 bits. > +set pac_bits_count 7 > + > +# A couple patterns that we reuse for the tests later. One is for a successful > +# memory read and the other is for a memory read failure. > +set memory_read_ok_pattern "$hex\( \)?:\[ \t\]+$hex" > +set memory_read_fail_pattern "$hex:\[ \t\]+Cannot access memory at address $hex" > + > +set pac_enabled 0 > + > +# Check if PAC is enabled. > +gdb_test_multiple "ptype \$pauth_cmask" "fetch PAC cmask" { > + -re "type = long\r\n$gdb_prompt" { > + set pac_enabled 1 > + } > + -re "type = void\r\n$gdb_prompt" { > + } > + -re ".*$gdb_prompt $" { > + fail $gdb_test_name > + return 1 > + } > +} > + > +# Value of the cmask register. > +set cmask 0 > + > +# If there are PAC registers, GDB uses those to unmask the PAC bits. > +if {$pac_enabled} { > + set cmask [get_valueof "" "\$pauth_cmask >> 48" "0" "fetch PAC cmask"] > +} > + > +# Cycle through the tag and pac bit ranges and check how GDB > +# behaves when trying to access these addresses. > +foreach upper_bits {"0x0" "0x1" "0x2" "0x4" "0x8" "0x10" "0x20" "0x40" "0x80"} { > + foreach lower_bits {"0x0" "0x1" "0x2" "0x4" "0x8" "0x10" "0x20" "0x40"} { > + > + # A successful memory read pattern > + set pattern $memory_read_ok_pattern > + > + if {!$pac_enabled} { > + # If PAC is not supported, memory reads will fail if > + # lower_bits != 0x0 > + if {$lower_bits != "0x0"} { > + set pattern $memory_read_fail_pattern > + } > + } else { > + # Otherwise, figure out if the memory read will succeed or not by > + # checking cmask. > + gdb_test_multiple "p/x (~${cmask}ULL & (${lower_bits}ULL))" "" { > + -re "= 0x0\r\n$gdb_prompt" { > + # Either cmask is 0x7F or lower_bits is 0x0. Either way, the > + # memory read should succeed. > + } > + -re "= $hex\r\n$gdb_prompt" { > + if {$lower_bits != "0x0"} { > + # cmask doesn't mask off all the PAC bits, which > + # results in a memory read failure, with the actual > + # address being accessed differing from the one we > + # passed. > + set pattern $memory_read_fail_pattern > + } > + } > + } > + } > + > + # Test without the VA_RANGE_SELECT bit set. > + gdb_test "x/gx ((unsigned long) l_ptr | ((${upper_bits}ULL << 56) | (${lower_bits}ULL << 48)))" \ > + $pattern \ > + "user-space memory access tag bits $upper_bits and pac bits $lower_bits" > + > + # Now test with the VA_RANGE_SELECT bit set. > + gdb_test "x/gx ((unsigned long) l_ptr | ((${upper_bits}ULL << 56) | (${lower_bits}ULL << 48) | (1ULL << 55))) " \ > + $memory_read_fail_pattern \ > + "kernel-space memory access tag bits $upper_bits and pac bits $lower_bits" > + } > +} > diff --git a/gdb/utils.c b/gdb/utils.c > index b0841e1fe5e..cf3db813777 100644 > --- a/gdb/utils.c > +++ b/gdb/utils.c > @@ -3139,28 +3139,6 @@ show_debug_timestamp (struct ui_file *file, int from_tty, > } > > > -/* See utils.h. */ > - > -CORE_ADDR > -address_significant (gdbarch *gdbarch, CORE_ADDR addr) > -{ > - /* Clear insignificant bits of a target address and sign extend resulting > - address, avoiding shifts larger or equal than the width of a CORE_ADDR. > - The local variable ADDR_BIT stops the compiler reporting a shift overflow > - when it won't occur. Skip updating of target address if current target > - has not set gdbarch significant_addr_bit. */ > - int addr_bit = gdbarch_significant_addr_bit (gdbarch); > - > - if (addr_bit && (addr_bit < (sizeof (CORE_ADDR) * HOST_CHAR_BIT))) > - { > - CORE_ADDR sign = (CORE_ADDR) 1 << (addr_bit - 1); > - addr &= ((CORE_ADDR) 1 << addr_bit) - 1; > - addr = (addr ^ sign) - sign; > - } > - > - return addr; > -} > - > const char * > paddress (struct gdbarch *gdbarch, CORE_ADDR addr) > { > diff --git a/gdb/utils.h b/gdb/utils.h > index d2acf899ba2..237ef0a5d99 100644 > --- a/gdb/utils.h > +++ b/gdb/utils.h > @@ -278,9 +278,6 @@ extern void fputs_styled (const char *linebuffer, > extern void fputs_highlighted (const char *str, const compiled_regex &highlight, > struct ui_file *stream); > > -/* Return the address only having significant bits. */ > -extern CORE_ADDR address_significant (gdbarch *gdbarch, CORE_ADDR addr); > - > /* Convert CORE_ADDR to string in platform-specific manner. > This is usually formatted similar to 0x%lx. */ > extern const char *paddress (struct gdbarch *gdbarch, CORE_ADDR addr); > diff --git a/gdbserver/linux-aarch64-low.cc b/gdbserver/linux-aarch64-low.cc > index db508696261..155706f1138 100644 > --- a/gdbserver/linux-aarch64-low.cc > +++ b/gdbserver/linux-aarch64-low.cc > @@ -508,21 +508,36 @@ aarch64_target::low_remove_point (raw_bkpt_type type, CORE_ADDR addr, > return ret; > } > > -/* Return the address only having significant bits. This is used to ignore > - the top byte (TBI). */ > - > static CORE_ADDR > -address_significant (CORE_ADDR addr) > +aarch64_remove_non_address_bits (CORE_ADDR pointer) > { > - /* Clear insignificant bits of a target address and sign extend resulting > - address. */ > - int addr_bit = 56; > + /* By default, we assume TBI and discard the top 8 bits plus the > + VA range select bit (55). */ > + CORE_ADDR mask = AARCH64_TOP_BITS_MASK; > + > + /* Check if PAC is available for this target. */ > + if (tdesc_contains_feature (current_process ()->tdesc, > + "org.gnu.gdb.aarch64.pauth")) > + { > + /* Fetch the PAC masks. These masks are per-process, so we can just > + fetch data from whatever thread we have at the moment. > + > + Also, we have both a code mask and a data mask. For now they are the > + same, but this may change in the future. */ > > - CORE_ADDR sign = (CORE_ADDR) 1 << (addr_bit - 1); > - addr &= ((CORE_ADDR) 1 << addr_bit) - 1; > - addr = (addr ^ sign) - sign; > + struct regcache *regs = get_thread_regcache (current_thread, 1); > + CORE_ADDR dmask = regcache_raw_get_unsigned_by_name (regs, "pauth_dmask"); > + CORE_ADDR cmask = regcache_raw_get_unsigned_by_name (regs, "pauth_cmask"); > + > + if (dmask != cmask && dmask != 0 && cmask != 0) > + { > + /* Warn if the masks are different. */ > + aarch64_pauth_mask_warning (); > + mask |= (dmask > cmask)? dmask : cmask; > + } > + } > > - return addr; > + return aarch64_remove_top_bits (pointer, mask); > } > > /* Implementation of linux target ops method "low_stopped_data_address". */ > @@ -549,7 +564,7 @@ aarch64_target::low_stopped_data_address () > hardware watchpoint hit. The stopped data addresses coming from the > kernel can potentially be tagged addresses. */ > const CORE_ADDR addr_trap > - = address_significant ((CORE_ADDR) siginfo.si_addr); > + = aarch64_remove_non_address_bits ((CORE_ADDR) siginfo.si_addr); > > /* Check if the address matches any watched address. */ > state = aarch64_get_debug_reg_state (pid_of (current_thread));