Gnu-morello December 2020

gnu-morello@op-lists.linaro.org

2 participants
3 discussions

Re: [Gnu-morello] [PATCH] [Morello] CHERI-style compact printing format

by Luis Machado

Hi, On 12/21/20 7:38 PM, J.R.T. Clarke wrote: > Hi Luis, >> >> @@ -556,20 +539,79 @@ capability::set_offset (uint64_t offset) >> ... >> + - (2) - If the top 64 bits are non-zero and the representation is >> + COMPACT, the capability has the following format: >> + > > You're missing documentation for this format. > Indeed. I've added the generic format from the documentation. >> ... >> + /* Handle attributes. */ >> + if (get_tag () == false) >> + attr_str = "invalid "; >> + if (get_otype () == CAP_SEAL_TYPE_RB) >> + attr_str = "sentry "; >> + if (is_sealed ()) >> + attr_str = "sealed "; > > These are supposed to be comma-separated, with no trailing space. > For some reason I missed the comma-separate entry. Fixed now. > Also sentries are not printed as sealed capabilities (but see below). > >> + cap_str += "{"; > > There are no curly braces in the specification. > I've added this one due to how GDB prints things. When showing the list of arguments for a function, it looks slightly confusing where things begin and end. >> + cap_str = val_str + " [" + perm_str + "," + range_str + "]"; >> + >> + if (!attr_str.empty ()) >> + cap_str += " ( " + attr_str + ")"; > > There should be no leading space. > Fixed. > I also couldn't help but notice you have the following: > >> inline bool is_sealed (void) >> { >> return check_permissions (CAP_PERM_SEAL); >> } > > (in capability.h) > > Whether a capability is sealed and whether a capability can be used to > seal are not the same thing. Good catch. I think I had the right idea (since I check otype in some other place), but ended up handling the sealed property incorrectly. Fixed now locally. I will push later. Thanks!

5 years, 1 month

Re: [Gnu-morello] [PATCH] [Morello] CHERI-style compact printing format

by J.R.T. Clarke

[resending with the right From:...] Hi Luis, > > @@ -556,20 +539,79 @@ capability::set_offset (uint64_t offset) > ... > + - (2) - If the top 64 bits are non-zero and the representation is > + COMPACT, the capability has the following format: > + You're missing documentation for this format. > ... > + /* Handle attributes. */ > + if (get_tag () == false) > + attr_str = "invalid "; > + if (get_otype () == CAP_SEAL_TYPE_RB) > + attr_str = "sentry "; > + if (is_sealed ()) > + attr_str = "sealed "; These are supposed to be comma-separated, with no trailing space. Also sentries are not printed as sealed capabilities (but see below). > + cap_str += "{"; There are no curly braces in the specification. > + cap_str = val_str + " [" + perm_str + "," + range_str + "]"; > + > + if (!attr_str.empty ()) > + cap_str += " ( " + attr_str + ")"; There should be no leading space. I also couldn't help but notice you have the following: > inline bool is_sealed (void) > { > return check_permissions (CAP_PERM_SEAL); > } (in capability.h) Whether a capability is sealed and whether a capability can be used to seal are not the same thing. Jess

5 years, 1 month

[PATCH] [Morello] CHERI-style compact printing format

by Luis Machado

This patch adds CHERI-style compact printing format to GDB and uses it by default. gdbsupport/ChangeLog: YYYY-MM-DD Luis Machado <luis.machado(a)arm.com> * capability.cc (cap_short_perms_strings): Remove. (capability::is_null_derived): New member function. (capability::to_str): Document and handle new CHERY-style printing format. * capability.h (cap_constants): Document the CAP_SEAL_TYPE_* constants. (struct capability) <is_null_derived>: New member function prototype. --- gdbsupport/capability.cc | 118 ++++++++++++++++++++++++++------------- gdbsupport/capability.h | 8 +++ 2 files changed, 88 insertions(+), 38 deletions(-) diff --git a/gdbsupport/capability.cc b/gdbsupport/capability.cc index 6551bab678..5ced9b6762 100644 --- a/gdbsupport/capability.cc +++ b/gdbsupport/capability.cc @@ -76,31 +76,6 @@ static const char *cap_perms_strings[] = "Load" }; -/* Short version of permission string names, indexed by bit number from - permissions - Valid bits are 0 through 17. */ -static const char *cap_short_perms_strings[] = -{ - "G", - "E", - "U0", - "U1", - "U2", - "U3", - "MLd", - "CID", - "BrUn", - "Sys", - "Un", - "Sl", - "StLoC", - "StC", - "LdC", - "X", - "St", - "Ld" -}; - /* Returns a capability, derived from the input capability, with base address set to the value of the input capability and the length set to a given value. If precise bounds setting is not possible, either the bounds are @@ -548,6 +523,14 @@ capability::set_offset (uint64_t offset) set_value (get_base () + offset); } +/* Returns true if the capability has the top 64 bits equal to zero. + Returns false otherwise. */ + +bool capability::is_null_derived (void) +{ + return _bits (m_cap, 127, 64) == 0; +} + /* Returns a string representation of the capability. If COMPACT is true, use a less verbose form. Otherwise print @@ -556,20 +539,79 @@ capability::set_offset (uint64_t offset) std::string capability::to_str (bool compact) { - /* The printing format is the following: - {tag = %d, address = 0x%016x, permissions = {[%s], otype = 0x%04x, - [range = [0x%016x - 0x%016x)}} + /* There are 3 printing formats. + + - (1) - If the top 64 bits are 0 and the tag is false, then we should print + the capability's value as a pointer. Example: 0xdeadbeef. + + - (2) - If the top 64 bits are non-zero and the representation is + COMPACT, the capability has the following format: + + - (3) - If the top 64 bits are non-zero and the representation is not + COMPACT, the capability has the following format: + + {tag = %d, address = 0x%016x, permissions = {[%s], otype = 0x%04x, + [range = [0x%016x - 0x%016x)}} */ - std::string cap_str (""); - std::string tag_str (get_tag ()? "1" : "0"); + std::string val_str (""); - std::string perm_str (""); - std::string otype_str (""); - std::string range_str (""); /* Capability value. */ val_str += core_addr_to_string_nz (get_value ()); + /* Format 1. */ + if (is_null_derived ()) + return val_str; + + std::string cap_str (""); + std::string perm_str (""); + std::string range_str (""); + + /* Format 2. */ + if (compact) + { + /* Handle compact permissions output. */ + if (check_permissions (1 << cap_perms_load)) + perm_str += "r"; + if (check_permissions (1 << cap_perms_store)) + perm_str += "w"; + if (check_permissions (1 << cap_perms_execute)) + perm_str += "x"; + if (check_permissions (1 << cap_perms_load_cap)) + perm_str += "R"; + if (check_permissions (1 << cap_perms_store_cap)) + perm_str += "W"; + if (check_permissions (1 << cap_perms_executive)) + perm_str += "E"; + + /* Handle capability range. */ + range_str += core_addr_to_string_nz (get_base ()); + range_str += "-"; + range_str += core_addr_to_string_nz (get_limit ()); + + std::string attr_str (""); + + /* Handle attributes. */ + if (get_tag () == false) + attr_str = "invalid "; + if (get_otype () == CAP_SEAL_TYPE_RB) + attr_str = "sentry "; + if (is_sealed ()) + attr_str = "sealed "; + + cap_str += "{"; + cap_str = val_str + " [" + perm_str + "," + range_str + "]"; + + if (!attr_str.empty ()) + cap_str += " ( " + attr_str + ")"; + + cap_str += "}"; + + return cap_str; + } + + /* Format 3. */ + /* Permissions. */ perm_str += "["; @@ -577,15 +619,13 @@ capability::to_str (bool compact) if (check_permissions (1 << i)) { perm_str += " "; - - if (compact) - perm_str += cap_short_perms_strings[i]; - else - perm_str += cap_perms_strings[i]; + perm_str += cap_perms_strings[i]; } perm_str += " ]"; + std::string otype_str (""); + /* Object type, if sealed. */ otype_str += core_addr_to_string_nz (get_otype ()); @@ -596,6 +636,8 @@ capability::to_str (bool compact) range_str += core_addr_to_string_nz (get_limit ()); range_str += ")"; + std::string tag_str (get_tag ()? "1" : "0"); + /* Assemble the capability string. */ cap_str += "{tag = " + tag_str + ", address = " + val_str + ", " + "permissions = {" + perm_str + " "; diff --git a/gdbsupport/capability.h b/gdbsupport/capability.h index fd94768e43..d77d8094a1 100644 --- a/gdbsupport/capability.h +++ b/gdbsupport/capability.h @@ -250,8 +250,11 @@ enum cap_constants { CAP_PERM_LOAD = (1<<17), CAP_PERM_LOAD_BIT = CAP_PERMS_LO_BIT+17, + /* Equivalent to CHERI's OTYPE_RESERVED3. */ CAP_SEAL_TYPE_LB = 3, + /* Equivalent to CHERI's OTYPE_RESERVED2. */ CAP_SEAL_TYPE_LPB = 2, + /* Equivalent to CHERI's OTYPE_SENTRY. */ CAP_SEAL_TYPE_RB = 1, CAP_TAG_BIT = 128, @@ -542,6 +545,11 @@ struct capability { otherwise. */ bool is_equal (void) const; + /* Returns true if the capability has the top 64 bits equal to zero. + Returns false otherwise. */ + + bool is_null_derived (void); + /* Printing functions. */ /* Returns a string representation of the capability. -- 2.25.1

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Gnu-morello December 2020