[PATCH v3 01/16] [gdb/aarch64] Fix register fetch/store order for native AArch64 Linux

Luis Machado via Gdb-patches
2023-06-30T13:47:15Z

I noticed we don't handle register reads/writes in the best way for native
AArch64 Linux. Some registers are fetched/stored even if upper level code
told us to fetch a particular register number.

Fix this by being more strict about which registers we touch when
reading/writing them in the native AArch64 Linux layer.

There should be no user-visible changes due to this patch.

Regression-tested on aarch64-linux Ubuntu 22.04/20.04.
---
gdb/aarch64-linux-nat.c | 60 ++++++++++++++++++++++-------------------
1 file changed, 33 insertions(+), 27 deletions(-)

diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index ecb2eeb9540..62656a7347b 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -504,6 +504,7 @@ aarch64_fetch_registers (struct regcache *regcache, int regno)
aarch64_gdbarch_tdep *tdep
= gdbarch_tdep<aarch64_gdbarch_tdep> (regcache->arch ());

+ /* Do we need to fetch all registers? */
if (regno == -1)
{
fetch_gregs_from_thread (regcache);
@@ -521,28 +522,28 @@ aarch64_fetch_registers (struct regcache *regcache, int regno)
if (tdep->has_tls ())
fetch_tlsregs_from_thread (regcache);
}
+ /* General purpose register? */
else if (regno < AARCH64_V0_REGNUM)
fetch_gregs_from_thread (regcache);
- else if (tdep->has_sve ())
+ /* SVE register? */
+ else if (tdep->has_sve () && regno <= AARCH64_SVE_VG_REGNUM)
fetch_sveregs_from_thread (regcache);
- else
+ /* FPSIMD register? */
+ else if (regno < AARCH64_FPCR_REGNUM)
fetch_fpregs_from_thread (regcache);
-
- if (tdep->has_pauth ())
- {
- if (regno == AARCH64_PAUTH_DMASK_REGNUM (tdep->pauth_reg_base)
- || regno == AARCH64_PAUTH_CMASK_REGNUM (tdep->pauth_reg_base))
- fetch_pauth_masks_from_thread (regcache);
- }
-
- /* Fetch individual MTE registers. */
- if (tdep->has_mte ()
- && (regno == tdep->mte_reg_base))
+ /* PAuth register? */
+ else if (tdep->has_pauth ()
+ && (regno == AARCH64_PAUTH_DMASK_REGNUM (tdep->pauth_reg_base)
+ || regno == AARCH64_PAUTH_CMASK_REGNUM (tdep->pauth_reg_base)))
+ fetch_pauth_masks_from_thread (regcache);
+ /* MTE register? */
+ else if (tdep->has_mte ()
+ && (regno == tdep->mte_reg_base))
fetch_mteregs_from_thread (regcache);
-
- if (tdep->has_tls ()
- && regno >= tdep->tls_regnum_base
- && regno < tdep->tls_regnum_base + tdep->tls_register_count)
+ /* TLS register? */
+ else if (tdep->has_tls ()
+ && regno >= tdep->tls_regnum_base
+ && regno < tdep->tls_regnum_base + tdep->tls_register_count)
fetch_tlsregs_from_thread (regcache);
}

@@ -592,6 +593,7 @@ aarch64_store_registers (struct regcache *regcache, int regno)
aarch64_gdbarch_tdep *tdep
= gdbarch_tdep<aarch64_gdbarch_tdep> (regcache->arch ());

+ /* Do we need to store all registers? */
if (regno == -1)
{
store_gregs_to_thread (regcache);
@@ -606,22 +608,26 @@ aarch64_store_registers (struct regcache *regcache, int regno)
if (tdep->has_tls ())
store_tlsregs_to_thread (regcache);
}
+ /* General purpose register? */
else if (regno < AARCH64_V0_REGNUM)
store_gregs_to_thread (regcache);
- else if (tdep->has_sve ())
+ /* SVE register? */
+ else if (tdep->has_sve () && regno <= AARCH64_SVE_VG_REGNUM)
store_sveregs_to_thread (regcache);
- else
+ /* FPSIMD register? */
+ else if (regno < AARCH64_FPCR_REGNUM)
store_fpregs_to_thread (regcache);
-
- /* Store MTE registers. */
- if (tdep->has_mte ()
- && (regno == tdep->mte_reg_base))
+ /* MTE register? */
+ else if (tdep->has_mte ()
+ && (regno == tdep->mte_reg_base))
store_mteregs_to_thread (regcache);
-
- if (tdep->has_tls ()
- && regno >= tdep->tls_regnum_base
- && regno < tdep->tls_regnum_base + tdep->tls_register_count)
+ /* TLS register? */
+ else if (tdep->has_tls ()
+ && regno >= tdep->tls_regnum_base
+ && regno < tdep->tls_regnum_base + tdep->tls_register_count)
store_tlsregs_to_thread (regcache);
+
+ /* PAuth registers are read-only. */
}

/* A version of the "store_registers" target_ops method used when running
--
2.25.1