[PATCH V2 7/7] arm64/hw_breakpoint: Enable FEAT_Debugv8p9

Anshuman Khandual
2024-10-28T05:51:48Z

Currently there can be maximum 16 breakpoints, and 16 watchpoints available
on a given platform - as detected from ID_AA64DFR0_EL1.[BRPs|WRPs] register
fields. But these breakpoint, and watchpoints can be extended further up to
64 via a new arch feature FEAT_Debugv8p9.

This first enables banked access for the breakpoint and watchpoint register
set via MDSELR_EL1, extended exceptions via MDSCR_EL1.EMBWE and determining
available breakpoints and watchpoints in the platform from ID_AA64DFR1_EL1,
when FEAT_Debugv8p9 is enabled.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Changes in V2:

- Alphabetically order header files in debug-monitors.c
- Dropped embwe_ref_count mechanism
- Dropped preempt_enable() from AARCH64_DBG_READ
- Dropped preempt_disable() from AARCH64_DBG_WRITE
- Dropped set_bank_index()
- Renamed read/write_wb_reg() as __read/__write_wb_reg()
- Modified read/write_wb_reg() to have MDSELR_E1 based banked read/write

arch/arm64/include/asm/debug-monitors.h | 1 +
arch/arm64/include/asm/hw_breakpoint.h | 46 +++++++++++++++++++------
arch/arm64/kernel/debug-monitors.c | 15 +++++---
arch/arm64/kernel/hw_breakpoint.c | 38 ++++++++++++++++++--
4 files changed, 84 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h
index 13d437bcbf58..a14097673ae0 100644
--- a/arch/arm64/include/asm/debug-monitors.h
+++ b/arch/arm64/include/asm/debug-monitors.h
@@ -20,6 +20,7 @@
#define DBG_MDSCR_KDE (1 << 13)
#define DBG_MDSCR_MDE (1 << 15)
#define DBG_MDSCR_MASK ~(DBG_MDSCR_KDE | DBG_MDSCR_MDE)
+#define DBG_MDSCR_EMBWE (1UL << 32)

#define DBG_ESR_EVT(x) (((x) >> 27) & 0x7)

diff --git a/arch/arm64/include/asm/hw_breakpoint.h b/arch/arm64/include/asm/hw_breakpoint.h
index bd81cf17744a..ec7c7901c61a 100644
--- a/arch/arm64/include/asm/hw_breakpoint.h
+++ b/arch/arm64/include/asm/hw_breakpoint.h
@@ -79,8 +79,8 @@ static inline void decode_ctrl_reg(u32 reg,
* Limits.
* Changing these will require modifications to the register accessors.
*/
-#define ARM_MAX_BRP 16
-#define ARM_MAX_WRP 16
+#define ARM_MAX_BRP 64
+#define ARM_MAX_WRP 64

/* Virtual debug register bases. */
#define AARCH64_DBG_REG_BVR 0
@@ -94,6 +94,14 @@ static inline void decode_ctrl_reg(u32 reg,
#define AARCH64_DBG_REG_NAME_WVR wvr
#define AARCH64_DBG_REG_NAME_WCR wcr

+static inline bool is_debug_v8p9_enabled(void)
+{
+ u64 dfr0 = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
+ int dver = cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_DebugVer_SHIFT);
+
+ return dver == ID_AA64DFR0_EL1_DebugVer_V8P9;
+}
+
/* Accessor macros for the debug registers. */
#define AARCH64_DBG_READ(N, REG, VAL) do {\
VAL = read_sysreg(dbg##REG##N##_el1);\
@@ -138,19 +146,37 @@ static inline void ptrace_hw_copy_thread(struct task_struct *task)
/* Determine number of BRP registers available. */
static inline int get_num_brps(void)
{
- u64 dfr0 = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
- return 1 +
- cpuid_feature_extract_unsigned_field(dfr0,
- ID_AA64DFR0_EL1_BRPs_SHIFT);
+ u64 dfr0, dfr1;
+ int dver, brps;
+
+ dfr0 = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
+ dver = cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_DebugVer_SHIFT);
+ if (dver == ID_AA64DFR0_EL1_DebugVer_V8P9) {
+ dfr1 = read_sanitised_ftr_reg(SYS_ID_AA64DFR1_EL1);
+ brps = cpuid_feature_extract_unsigned_field_width(dfr1,
+ ID_AA64DFR1_EL1_BRPs_SHIFT, 8);
+ } else {
+ brps = cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_BRPs_SHIFT);
+ }
+ return 1 + brps;
}

/* Determine number of WRP registers available. */
static inline int get_num_wrps(void)
{
- u64 dfr0 = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
- return 1 +
- cpuid_feature_extract_unsigned_field(dfr0,
- ID_AA64DFR0_EL1_WRPs_SHIFT);
+ u64 dfr0, dfr1;
+ int dver, wrps;
+
+ dfr0 = read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1);
+ dver = cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_DebugVer_SHIFT);
+ if (dver == ID_AA64DFR0_EL1_DebugVer_V8P9) {
+ dfr1 = read_sanitised_ftr_reg(SYS_ID_AA64DFR1_EL1);
+ wrps = cpuid_feature_extract_unsigned_field_width(dfr1,
+ ID_AA64DFR1_EL1_WRPs_SHIFT, 8);
+ } else {
+ wrps = cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_WRPs_SHIFT);
+ }
+ return 1 + wrps;
}

#ifdef CONFIG_CPU_PM
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 024a7b245056..b56716c654d8 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -21,6 +21,7 @@
#include <asm/cputype.h>
#include <asm/daifflags.h>
#include <asm/debug-monitors.h>
+#include <asm/hw_breakpoint.h>
#include <asm/system_misc.h>
#include <asm/traps.h>

@@ -34,7 +35,7 @@ u8 debug_monitors_arch(void)
/*
* MDSCR access routines.
*/
-static void mdscr_write(u32 mdscr)
+static void mdscr_write(u64 mdscr)
{
unsigned long flags;
flags = local_daif_save();
@@ -43,7 +44,7 @@ static void mdscr_write(u32 mdscr)
}
NOKPROBE_SYMBOL(mdscr_write);

-static u32 mdscr_read(void)
+static u64 mdscr_read(void)
{
return read_sysreg(mdscr_el1);
}
@@ -79,7 +80,7 @@ static DEFINE_PER_CPU(int, kde_ref_count);

void enable_debug_monitors(enum dbg_active_el el)
{
- u32 mdscr, enable = 0;
+ u64 mdscr, enable = 0;

WARN_ON(preemptible());

@@ -90,6 +91,9 @@ void enable_debug_monitors(enum dbg_active_el el)
this_cpu_inc_return(kde_ref_count) == 1)
enable |= DBG_MDSCR_KDE;

+ if (is_debug_v8p9_enabled())
+ enable |= DBG_MDSCR_EMBWE;
+
if (enable && debug_enabled) {
mdscr = mdscr_read();
mdscr |= enable;
@@ -100,7 +104,7 @@ NOKPROBE_SYMBOL(enable_debug_monitors);

void disable_debug_monitors(enum dbg_active_el el)
{
- u32 mdscr, disable = 0;
+ u64 mdscr, disable = 0;

WARN_ON(preemptible());

@@ -111,6 +115,9 @@ void disable_debug_monitors(enum dbg_active_el el)
this_cpu_dec_return(kde_ref_count) == 0)
disable &= ~DBG_MDSCR_KDE;

+ if (is_debug_v8p9_enabled())
+ disable &= ~DBG_MDSCR_EMBWE;
+
if (disable) {
mdscr = mdscr_read();
mdscr &= disable;
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index 722ac45f9f7b..630db607ca2b 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -103,7 +103,7 @@ int hw_breakpoint_slots(int type)
WRITE_WB_REG_CASE(OFF, 14, REG, VAL); \
WRITE_WB_REG_CASE(OFF, 15, REG, VAL)

-static u64 read_wb_reg(int reg, int n)
+static u64 __read_wb_reg(int reg, int n)
{
u64 val = 0;

@@ -118,9 +118,27 @@ static u64 read_wb_reg(int reg, int n)

return val;
}
+
+static u64 read_wb_reg(int reg, int n)
+{
+ int mdsel_bank, index;
+ u64 val;
+
+ if (!is_debug_v8p9_enabled())
+ return __read_wb_reg(reg, n);
+
+ mdsel_bank = n / 16;
+ index = n % 16;
+ preempt_disable();
+ write_sysreg_s(mdsel_bank << MDSELR_EL1_BANK_SHIFT, SYS_MDSELR_EL1);
+ isb();
+ val = __read_wb_reg(reg, index);
+ preempt_enable();
+ return val;
+}
NOKPROBE_SYMBOL(read_wb_reg);

-static void write_wb_reg(int reg, int n, u64 val)
+static void __write_wb_reg(int reg, int n, u64 val)
{
switch (reg + n) {
GEN_WRITE_WB_REG_CASES(AARCH64_DBG_REG_BVR, AARCH64_DBG_REG_NAME_BVR, val);
@@ -132,6 +150,22 @@ static void write_wb_reg(int reg, int n, u64 val)
}
isb();
}
+
+static void write_wb_reg(int reg, int n, u64 val)
+{
+ int mdsel_bank, index;
+
+ if (!is_debug_v8p9_enabled())
+ return __write_wb_reg(reg, n, val);
+
+ mdsel_bank = n / 16;
+ index = n % 16;
+ preempt_disable();
+ write_sysreg_s(mdsel_bank << MDSELR_EL1_BANK_SHIFT, SYS_MDSELR_EL1);
+ isb();
+ __write_wb_reg(reg, index, val);
+ preempt_enable();
+}
NOKPROBE_SYMBOL(write_wb_reg);

/*
--
2.25.1