With suggestions applied.
Here we introduce the flags that will be used for straight line speculation.
The new flag introduced is `-mharden-sls=`.
This flag can take arguments of `none`, `all`, or a comma seperated list of one
or more of `retbr` or `blr`.
`none` indicates no special mitigation of the straight line speculation
vulnerability.
`all` requests all mitigations currently implemented.
`retbr` requests that the RET and BR instructions have a speculation barrier
inserted after them.
`blr` requests that BLR instructions are replaced by a BL to a function stub
using a BR with a speculation barrier after it.
Setting this on a per-function basis using attributes or the like is not
enabled, but may be in the future.
gcc/ChangeLog:
2020-07-03 Matthew Malcomson <matthew.malcom...@arm.com>
* config/aarch64/aarch64-protos.h (aarch64_harden_sls_retbr_p):
New.
(aarch64_harden_sls_blr_p): New.
* config/aarch64/aarch64.c (enum aarch64_sls_hardening_type):
New.
(aarch64_harden_sls_retbr_p): New.
(aarch64_harden_sls_blr_p): New.
(aarch64_validate_sls_mitigation): New.
(aarch64_override_options): Parse options for SLS mitigation.
* config/aarch64/aarch64.opt (-mharden-sls): New option.
* doc/invoke.texi: Document new option.
############### Attachment also inlined for ease of reply ###############
diff --git a/gcc/config/aarch64/aarch64-protos.h
b/gcc/config/aarch64/aarch64-protos.h
index
9e43adb7db0373df6cc5ef1d2b22f217aca2aad2..8ca67d7e69edaf73c84f079e7e1c483009ad10c0
100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -780,4 +780,7 @@ extern const atomic_ool_names aarch64_ool_ldeor_names;
tree aarch64_resolve_overloaded_builtin_general (location_t, tree, void *);
+extern bool aarch64_harden_sls_retbr_p (void);
+extern bool aarch64_harden_sls_blr_p (void);
+
#endif /* GCC_AARCH64_PROTOS_H */
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index
f3551a73d87c4e686540f39224985592c3c66fd1..b1a7c10c4eaadd78eb45926c23efc51a8272b5fd
100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -14502,6 +14502,80 @@ aarch64_validate_mcpu (const char *str, const struct
processor **res,
return false;
}
+/* Straight line speculation indicators. */
+enum aarch64_sls_hardening_type
+{
+ SLS_NONE = 0,
+ SLS_RETBR = 1,
+ SLS_BLR = 2,
+ SLS_ALL = 3,
+};
+static enum aarch64_sls_hardening_type aarch64_sls_hardening;
+
+/* Return whether we should mitigatate Straight Line Speculation for the RET
+ and BR instructions. */
+bool
+aarch64_harden_sls_retbr_p (void)
+{
+ return aarch64_sls_hardening & SLS_RETBR;
+}
+
+/* Return whether we should mitigatate Straight Line Speculation for the BLR
+ instruction. */
+bool
+aarch64_harden_sls_blr_p (void)
+{
+ return aarch64_sls_hardening & SLS_BLR;
+}
+
+/* As of yet we only allow setting these options globally, in the future we may
+ allow setting them per function. */
+static void
+aarch64_validate_sls_mitigation (const char *const_str)
+{
+ char *token_save = NULL;
+ char *str = NULL;
+
+ aarch64_sls_hardening = SLS_NONE;
+ if (strcmp (const_str, "none") == 0)
+ {
+ aarch64_sls_hardening = SLS_NONE;
+ return;
+ }
+ if (strcmp (const_str, "all") == 0)
+ {
+ aarch64_sls_hardening = SLS_ALL;
+ return;
+ }
+
+ char *str_root = xstrdup (const_str);
+ str = strtok_r (str_root, ",", &token_save);
+ if (!str)
+ error ("invalid argument given to %<-mharden-sls=%>");
+
+ int temp = SLS_NONE;
+ while (str)
+ {
+ if (strcmp (str, "blr") == 0)
+ temp |= SLS_BLR;
+ else if (strcmp (str, "retbr") == 0)
+ temp |= SLS_RETBR;
+ else if (strcmp (str, "none") == 0 || strcmp (str, "all") == 0)
+ {
+ error ("%<%s%> must be by itself for %<-mharden-sls=%>", str);
+ break;
+ }
+ else
+ {
+ error ("invalid argument %<%s%> for %<-mharden-sls=%>", str);
+ break;
+ }
+ str = strtok_r (NULL, ",", &token_save);
+ }
+ aarch64_sls_hardening = (aarch64_sls_hardening_type) temp;
+ free (str_root);
+}
+
/* Parses CONST_STR for branch protection features specified in
aarch64_branch_protect_types, and set any global variables required.
Returns
the parsing result and assigns LAST_STR to the last processed token from
@@ -14746,6 +14820,9 @@ aarch64_override_options (void)
selected_arch = NULL;
selected_tune = NULL;
+ if (aarch64_harden_sls_string)
+ aarch64_validate_sls_mitigation (aarch64_harden_sls_string);
+
if (aarch64_branch_protection_string)
aarch64_validate_mbranch_protection (aarch64_branch_protection_string);
diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index
d99d14c137d8774d3c8dab860d475f68c01a2817..5170361fd5e5721e044d1664e522b2718f654b8e
100644
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -71,6 +71,10 @@ mgeneral-regs-only
Target Report RejectNegative Mask(GENERAL_REGS_ONLY) Save
Generate code which uses only the general registers.
+mharden-sls=
+Target RejectNegative Joined Var(aarch64_harden_sls_string)
+Generate code to mitigate against straight line speculation.
+
mfix-cortex-a53-835769
Target Report Var(aarch64_fix_a53_err835769) Init(2) Save
Workaround for ARM Cortex-A53 Erratum number 835769.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index
98cc0f2f0de1d89928d98edcb2f2fa99f040f195..fd71f7c79019b681008d08284eff2878790b7ffa
100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -698,6 +698,7 @@ Objective-C and Objective-C++ Dialects}.
-msign-return-address=@var{scope} @gol
-mbranch-protection=@var{none}|@var{standard}|@var{pac-ret}[+@var{leaf}
+@var{b-key}]|@var{bti} @gol
+-mharden-sls=@var{opts} @gol
-march=@var{name} -mcpu=@var{name} -mtune=@var{name} @gol
-moverride=@var{string} -mverbose-cost-dump @gol
-mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{sysreg}
@gol
@@ -17367,6 +17368,17 @@ functions. The optional argument @samp{b-key} can be
used to sign the functions
with the B-key instead of the A-key.
@samp{bti} turns on branch target identification mechanism.
+@item -mharden-sls=@var{opts}
+@opindex mharden-sls
+Enable compiler hardening against straight line speculation (SLS).
+@var{opts} is a comma-separated list of the following options:
+@table @samp
+@item retbr
+@item blr
+@end table
+In addition, @samp{-mharden-sls=all} enables all SLS hardening while
+@samp{-mharden-sls=none} disables all SLS hardening.
+
@item -msve-vector-bits=@var{bits}
@opindex msve-vector-bits
Specify the number of bits in an SVE vector register. This option only has
diff --git a/gcc/config/aarch64/aarch64-protos.h
b/gcc/config/aarch64/aarch64-protos.h
index
9e43adb7db0373df6cc5ef1d2b22f217aca2aad2..8ca67d7e69edaf73c84f079e7e1c483009ad10c0
100644
--- a/gcc/config/aarch64/aarch64-protos.h
+++ b/gcc/config/aarch64/aarch64-protos.h
@@ -780,4 +780,7 @@ extern const atomic_ool_names aarch64_ool_ldeor_names;
tree aarch64_resolve_overloaded_builtin_general (location_t, tree, void *);
+extern bool aarch64_harden_sls_retbr_p (void);
+extern bool aarch64_harden_sls_blr_p (void);
+
#endif /* GCC_AARCH64_PROTOS_H */
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index
f3551a73d87c4e686540f39224985592c3c66fd1..b1a7c10c4eaadd78eb45926c23efc51a8272b5fd
100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -14502,6 +14502,80 @@ aarch64_validate_mcpu (const char *str, const struct
processor **res,
return false;
}
+/* Straight line speculation indicators. */
+enum aarch64_sls_hardening_type
+{
+ SLS_NONE = 0,
+ SLS_RETBR = 1,
+ SLS_BLR = 2,
+ SLS_ALL = 3,
+};
+static enum aarch64_sls_hardening_type aarch64_sls_hardening;
+
+/* Return whether we should mitigatate Straight Line Speculation for the RET
+ and BR instructions. */
+bool
+aarch64_harden_sls_retbr_p (void)
+{
+ return aarch64_sls_hardening & SLS_RETBR;
+}
+
+/* Return whether we should mitigatate Straight Line Speculation for the BLR
+ instruction. */
+bool
+aarch64_harden_sls_blr_p (void)
+{
+ return aarch64_sls_hardening & SLS_BLR;
+}
+
+/* As of yet we only allow setting these options globally, in the future we may
+ allow setting them per function. */
+static void
+aarch64_validate_sls_mitigation (const char *const_str)
+{
+ char *token_save = NULL;
+ char *str = NULL;
+
+ aarch64_sls_hardening = SLS_NONE;
+ if (strcmp (const_str, "none") == 0)
+ {
+ aarch64_sls_hardening = SLS_NONE;
+ return;
+ }
+ if (strcmp (const_str, "all") == 0)
+ {
+ aarch64_sls_hardening = SLS_ALL;
+ return;
+ }
+
+ char *str_root = xstrdup (const_str);
+ str = strtok_r (str_root, ",", &token_save);
+ if (!str)
+ error ("invalid argument given to %<-mharden-sls=%>");
+
+ int temp = SLS_NONE;
+ while (str)
+ {
+ if (strcmp (str, "blr") == 0)
+ temp |= SLS_BLR;
+ else if (strcmp (str, "retbr") == 0)
+ temp |= SLS_RETBR;
+ else if (strcmp (str, "none") == 0 || strcmp (str, "all") == 0)
+ {
+ error ("%<%s%> must be by itself for %<-mharden-sls=%>", str);
+ break;
+ }
+ else
+ {
+ error ("invalid argument %<%s%> for %<-mharden-sls=%>", str);
+ break;
+ }
+ str = strtok_r (NULL, ",", &token_save);
+ }
+ aarch64_sls_hardening = (aarch64_sls_hardening_type) temp;
+ free (str_root);
+}
+
/* Parses CONST_STR for branch protection features specified in
aarch64_branch_protect_types, and set any global variables required.
Returns
the parsing result and assigns LAST_STR to the last processed token from
@@ -14746,6 +14820,9 @@ aarch64_override_options (void)
selected_arch = NULL;
selected_tune = NULL;
+ if (aarch64_harden_sls_string)
+ aarch64_validate_sls_mitigation (aarch64_harden_sls_string);
+
if (aarch64_branch_protection_string)
aarch64_validate_mbranch_protection (aarch64_branch_protection_string);
diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index
d99d14c137d8774d3c8dab860d475f68c01a2817..5170361fd5e5721e044d1664e522b2718f654b8e
100644
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -71,6 +71,10 @@ mgeneral-regs-only
Target Report RejectNegative Mask(GENERAL_REGS_ONLY) Save
Generate code which uses only the general registers.
+mharden-sls=
+Target RejectNegative Joined Var(aarch64_harden_sls_string)
+Generate code to mitigate against straight line speculation.
+
mfix-cortex-a53-835769
Target Report Var(aarch64_fix_a53_err835769) Init(2) Save
Workaround for ARM Cortex-A53 Erratum number 835769.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index
98cc0f2f0de1d89928d98edcb2f2fa99f040f195..fd71f7c79019b681008d08284eff2878790b7ffa
100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -698,6 +698,7 @@ Objective-C and Objective-C++ Dialects}.
-msign-return-address=@var{scope} @gol
-mbranch-protection=@var{none}|@var{standard}|@var{pac-ret}[+@var{leaf}
+@var{b-key}]|@var{bti} @gol
+-mharden-sls=@var{opts} @gol
-march=@var{name} -mcpu=@var{name} -mtune=@var{name} @gol
-moverride=@var{string} -mverbose-cost-dump @gol
-mstack-protector-guard=@var{guard} -mstack-protector-guard-reg=@var{sysreg}
@gol
@@ -17367,6 +17368,17 @@ functions. The optional argument @samp{b-key} can be
used to sign the functions
with the B-key instead of the A-key.
@samp{bti} turns on branch target identification mechanism.
+@item -mharden-sls=@var{opts}
+@opindex mharden-sls
+Enable compiler hardening against straight line speculation (SLS).
+@var{opts} is a comma-separated list of the following options:
+@table @samp
+@item retbr
+@item blr
+@end table
+In addition, @samp{-mharden-sls=all} enables all SLS hardening while
+@samp{-mharden-sls=none} disables all SLS hardening.
+
@item -msve-vector-bits=@var{bits}
@opindex msve-vector-bits
Specify the number of bits in an SVE vector register. This option only has
