Merge pull request #5184 from p3n1cillin/claude/sysctl-vm-overcommit

feat(libkernel): report vm.overcommit through sysctlbyname

core/libs/prx/libkernel/System/src/SystemConfiguration.cpp

@@ -206,6 +206,11 @@ int APS5_VABI sysctlbyname_nid_postfix(const char* name, void* oldValue, std::si
         for (std::size_t i = 0; i < *oldLength; ++i) bytes[i] = static_cast<std::uint8_t>(device());
         return 0;
     }
+    if (std::strcmp(name, "vm.overcommit") == 0) {
+        if (newValue != nullptr) throw std::runtime_error(std::string(__func__) + ": setting vm.overcommit");
+        static constexpr int overcommit = 0;
+        return CopyOut(&overcommit, sizeof(overcommit), oldValue, oldLength);
+    }
     if (std::strcmp(name, "kern.sdk_version") == 0) {
         if (newValue != nullptr) {
             *__error_nid_postfix() = 1;

core/libs/tests/GuestSystemConfiguration.cpp

@@ -219,6 +219,27 @@ static void CheckPseudoRandomSysctl() {
     }
     Require(threw);
 }
+static void CheckOvercommitSysctl() {
+    *__error_nid_postfix() = 13;
+    std::size_t length = 0;
+    Require(sysctlbyname_nid_postfix("vm.overcommit", nullptr, &length, nullptr, 0) == 0 && length == sizeof(int));
+    int value = -1;
+    length = sizeof(value);
+    Require(sysctlbyname_nid_postfix("vm.overcommit", &value, &length, nullptr, 0) == 0 && value == 0 && length == sizeof(int));
+    Require(*__error_nid_postfix() == 13);
+    unsigned char bytes[4] = {0xaa, 0xaa, 0xaa, 0xaa};
+    length = 2;
+    Require(sysctlbyname_nid_postfix("vm.overcommit", bytes, &length, nullptr, 0) == -1 && *__error_nid_postfix() == 12);
+    Require(length == 2 && bytes[2] == 0xaa && bytes[3] == 0xaa);
+    bool threw = false;
+    length = sizeof(value);
+    try {
+        sysctlbyname_nid_postfix("vm.overcommit", &value, &length, &value, sizeof(value));
+    } catch (const std::runtime_error&) {
+        threw = true;
+    }
+    Require(threw);
+}
 static void CheckSdkVersionSysctl() {
     *__error_nid_postfix() = 13;
     std::size_t length = 0;
@@ -282,6 +303,7 @@ int main() {
     CheckSystemSwVersion();
     CheckPseudoRandomSysctl();
     CheckSdkVersionSysctl();
+    CheckOvercommitSysctl();
     CheckArandomSysctl();
     *__error_nid_postfix() = 13;
     Require(sysconf_nid_postfix(3) == 128);

docs/dev/debt/libkernel.md

@@ -17,6 +17,7 @@
 - [kern.rng_pseudo](../../../core/libs/prx/libkernel/System/src/SystemConfiguration.cpp) (libkernel) - `sysctlbyname` fills the whole output buffer with bytes from the host's `std::random_device` and leaves the length unchanged; a write returns -1 with `EPERM` and a call without an output buffer throws. The only caller seen is mbedTLS's `mbedtls_hardware_poll` in the catalog's ProsperoLight boilerplate, which asks for 64-byte blocks and fails if fewer come back. The console's generator, its per-call maximum and its answer to a size query are unknown
 - [sysconf](../../../core/libs/prx/libkernel/System/src/SystemConfiguration.cpp) (libkernel) - `_SC_CLK_TCK` returns 128, FreeBSD's `CLK_TCK` as its [`sysconf`](https://github.com/freebsd/freebsd-src/blob/8c639945a44588f6cfdddfb057bb5aad88735da0/lib/libc/gen/sysconf.c#L100-L101) returns it ([`time.h`](https://github.com/freebsd/freebsd-src/blob/8c639945a44588f6cfdddfb057bb5aad88735da0/include/time.h#L48-L54)); the console's value is not checked, and no `times` reports ticks at that rate. CPython's `posix` module stops its import with "cannot read ticks_per_second" when the value is below 1, as the Python in PS5MC (PPSA99420) does. Names other than `_SC_CLK_TCK`, `_SC_PAGESIZE`, `_SC_NPROCESSORS_CONF`, `_SC_NPROCESSORS_ONLN` and `_SC_PHYS_PAGES` fail with `EINVAL`
 - [hw.realmem](../../../core/libs/prx/libkernel/System/src/SystemConfiguration.cpp) (libkernel) - `sysctl` {`CTL_HW`, 12} and `sysctlbyname` report the same 8-byte value as `hw.physmem` (the `_SC_PHYS_PAGES` pages of 16 KiB), read-only with `EPERM` for a write and `ENOMEM` for a short buffer, as FreeBSD's [`sysctl_hw_realmem`](https://github.com/freebsd/freebsd-src/blob/8c639945a44588f6cfdddfb057bb5aad88735da0/sys/kern/kern_mib.c#L191-L204) does. FreeBSD reports there the memory the firmware describes, which is at least `hw.physmem`; the console's values are not known. Dolphin reads it as the machine's memory size in [`MemPhysical`](https://github.com/dolphin-emu/dolphin/blob/8d2ad1a662472955497e5bb79d7b9ec6999e1f0d/Source/Core/Common/MemoryUtil.cpp#L253-L273) (RetroArch PPSA99169's `dolphin_libretro` core)
+- [vm.overcommit](../../../core/libs/prx/libkernel/System/src/SystemConfiguration.cpp) (libkernel) - `sysctlbyname` reports the 4-byte value 0, the default FreeBSD gives its [`vm.overcommit`](https://github.com/freebsd/freebsd-src/blob/8c639945a44588f6cfdddfb057bb5aad88735da0/sys/vm/swap_pager.c#L158-L161) `int`, with `ENOMEM` for a short buffer; the console's value is not known and a write throws. mimalloc reads it in [`unix_detect_overcommit`](https://github.com/microsoft/mimalloc/blob/31d034d94cdb8e22f7d7ed55967f581a2d6e831d/src/prim/unix/prim.c#L129-L153) and takes 0 as no overcommit, as PS5MC (PPSA99420) does at start-up
 - [kern.sdk_version](../../../core/libs/prx/libkernel/System/src/SystemConfiguration.cpp) (libkernel) - `sysctlbyname` reports the system software version as the 4-byte value `0x01000000` (1.00), the value `sceKernelGetSystemSwVersion` reports; a write returns -1 with `EPERM`. The major version is byte 3 and the minor version byte 2, in hex digits that read as decimal (13.60 is `0x1360xxxx`), as [Capy Mobile](https://github.com/khalifa007/CapyMobile/blob/2758c016/src/ps5/platform.c#L64-L71) (PPSA92280), [remote_lua_loader](https://github.com/n0llptr/remote_lua_loader/blob/7c2840e475/savedata/misc.lua#L195-L209) and the [lapse payload](https://github.com/NetflixNHack/Netflix-N-Hack/blob/605eb93ba5/PS4/payloads/lapse.js#L436-L450) read it. Capy Mobile only displays it. The console's firmware version is not modeled and the low two bytes are unknown
 - [sceKernelGetProsperoSystemSwVersion](../../../core/libs/prx/libkernel/System/src/SoftwareVersion.cpp) (libkernel) reports system software version `0x01000000` ("01.000.000"); the console's firmware version is not modeled. The 0x28-byte block (a 64-bit size at 0, the version string at 8 and the packed version at 0x24) follows [SharpProspero](https://github.com/SvenGDK/SharpProspero/blob/main/src/SharpProspero/Interop/Kernel/KernelSystem.cs), which Prospero Multi Tools (PPSA99110) and Prospero Explorer (PPSA99109) are built with and which sets the size to 40, and the same fields in [etaHEN](https://github.com/etaHEN/etaHEN/blob/main/Source%20Code/daemon/include/ipc.hpp) and [shsrv](https://github.com/ps5-payload-dev/shsrv/blob/master/sh.c). A size other than 0x28 returns `SCE_KERNEL_ERROR_EINVAL` without writing; whether the console checks the size is unverified, since etaHEN and shsrv declare a 0x30-byte block and do not set it
 - [sceKernelGetAllowedSdkVersionOnSystem](../../../core/libs/prx/libkernel/System/src/SoftwareVersion.cpp) (libkernel) reports the system software version with the 12 patch bits set, `0x01000fff`, as [shadPS4](https://github.com/shadps4-emu/shadPS4/blob/98fd0689/src/core/libraries/kernel/kernel.cpp) does on the PS4 and as [SharpProspero](https://github.com/SvenGDK/SharpProspero/blob/main/src/SharpProspero/Interop/Kernel/KernelSystem.cs) describes it, which Prospero Explorer (PPSA99109) reads it through; a null pointer returns `SCE_KERNEL_ERROR_EINVAL`. The console's value and its errors are unverified