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plugins: add PC diversion API function

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This patch adds a plugin API function that allows diverting the program
counter during execution. A potential use case for this functionality is
to skip over parts of the code, e.g., by hooking into a specific
instruction and setting the PC to the next instruction in the callback.

Link: https://lists.nongnu.org/archive/html/qemu-devel/2025-08/msg00656.html
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Florian Hofhammer <florian.hofhammer@epfl.ch>
Link: https://lore.kernel.org/qemu-devel/20260305-setpc-v5-v7-4-4c3adba52403@epfl.ch
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
This commit is contained in:
Florian Hofhammer
2026-03-05 11:06:02 +01:00
committed by Pierrick Bouvier
parent 9097087147
commit 4f55cd7801
3 changed files with 31 additions and 2 deletions
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13
include/plugins/qemu-plugin.h
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@@ -76,6 +76,7 @@ typedef uint64_t qemu_plugin_id_t;
* *
* version 6: * version 6:
* - changed return value of qemu_plugin_{read,write}_register from int to bool * - changed return value of qemu_plugin_{read,write}_register from int to bool
* - added qemu_plugin_set_pc
*/ */
extern QEMU_PLUGIN_EXPORT int qemu_plugin_version; extern QEMU_PLUGIN_EXPORT int qemu_plugin_version;
@@ -1042,6 +1043,18 @@ QEMU_PLUGIN_API
bool qemu_plugin_write_register(struct qemu_plugin_register *handle, bool qemu_plugin_write_register(struct qemu_plugin_register *handle,
GByteArray *buf); GByteArray *buf);
/**
* qemu_plugin_set_pc() - set the program counter for the current vCPU
*
* @vaddr: the new virtual (guest) address for the program counter
*
* This function sets the program counter for the current vCPU to @vaddr and
* resumes execution at that address. This function does not return.
*/
QEMU_PLUGIN_API
__attribute__((__noreturn__))
void qemu_plugin_set_pc(uint64_t vaddr);
/** /**
* qemu_plugin_read_memory_vaddr() - read from memory using a virtual address * qemu_plugin_read_memory_vaddr() - read from memory using a virtual address
* *

11
plugins/api.c
View File

@@ -41,6 +41,7 @@
#include "qemu/log.h" #include "qemu/log.h"
#include "system/memory.h" #include "system/memory.h"
#include "tcg/tcg.h" #include "tcg/tcg.h"
#include "exec/cpu-common.h"
#include "exec/gdbstub.h" #include "exec/gdbstub.h"
#include "exec/target_page.h" #include "exec/target_page.h"
#include "exec/translation-block.h" #include "exec/translation-block.h"
@@ -467,6 +468,16 @@ bool qemu_plugin_write_register(struct qemu_plugin_register *reg,
return (gdb_write_register(current_cpu, buf->data, GPOINTER_TO_INT(reg) - 1) > 0); return (gdb_write_register(current_cpu, buf->data, GPOINTER_TO_INT(reg) - 1) > 0);
} }
void qemu_plugin_set_pc(uint64_t vaddr)
{
g_assert(current_cpu);
g_assert(qemu_plugin_get_cb_flags() == QEMU_PLUGIN_CB_RW_REGS_PC);
cpu_set_pc(current_cpu, vaddr);
cpu_loop_exit(current_cpu);
}
bool qemu_plugin_read_memory_vaddr(uint64_t addr, GByteArray *data, size_t len) bool qemu_plugin_read_memory_vaddr(uint64_t addr, GByteArray *data, size_t len)
{ {
g_assert(current_cpu); g_assert(current_cpu);

9
scripts/qemu-plugin-symbols.py
View File

@@ -20,9 +20,14 @@ def extract_symbols(plugin_header):
# Remove QEMU_PLUGIN_API macro definition. # Remove QEMU_PLUGIN_API macro definition.
content = content.replace('#define QEMU_PLUGIN_API', '') content = content.replace('#define QEMU_PLUGIN_API', '')
expected = content.count('QEMU_PLUGIN_API') expected = content.count('QEMU_PLUGIN_API')
# Find last word between QEMU_PLUGIN_API and (, matching on several lines. # Find last word between QEMU_PLUGIN_API and ( to get the function name,
# matching on several lines. Discard attributes, if any.
# We use *? non-greedy quantifier. # We use *? non-greedy quantifier.
syms = re.findall(r'QEMU_PLUGIN_API.*?(\w+)\s*\(', content, re.DOTALL) syms = re.findall(
r'QEMU_PLUGIN_API\s+(?:__attribute__\(\(\S+\)\))?.*?(\w+)\s*\(',
content,
re.DOTALL,
)
syms.sort() syms.sort()
# Ensure we found as many symbols as API markers. # Ensure we found as many symbols as API markers.
assert len(syms) == expected assert len(syms) == expected